NCHurricane2009's Blog

2016 Atlantic Hurricane Season Birdseye Discussion #133

By: NCHurricane2009, 10:53 AM GMT on September 30, 2016

...FRIDAY SEPTEMBER 30 2016 6:55 AM EDT...
Alert! Interests in Jamaica...Haiti...eastern Cuba...and Bahamas should begin thinking about preparations this weekend for early next week...for severe weather (highly damaging winds and flooding) from a possible major hurricane of extraordinary strength. Tropical Storm Matthew has continued to rapidly strengthen and is now a category 2 hurricane. With conditions remaining highly favorable for Matthew...this storm could become the first category 5 in the Atlantic basin since Felix in 2007. See first special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on Matthew...including for more information on its current strength as additional rapid strengthening could occur at any time.

In addition to Matthew...see the following statements for two other areas of interest...

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic in the atmospheric features chart below. The vigorous tropical wave which has recently emerged from western Africa has lost all thunderstorm activity except for a strong but small burst of thunderstorms just west of the Republic of Cabo Verde this morning. Its possible that this tropical wave will become unfavorably sheared by the westward-retrograding upper vortex in the eastern and central tropical Atlantic. However it is also possible that as this upper vortex weakens while it retrogrades...the deelopment of a more favorable upper ridge to the southeast of the upper vortex could reduce the shear. Therefore will continue to monitor this tropical wave.

The following statement concerns area of interest #2 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Satellite pictures suggest there is yet another vigorous tropical wave emerging into the eastern tropical Atlantic from western Africa. Additional development of this tropical wave is possible over the next few days as a more favorable upper ridge develops to the southeast of the weakening and retrograding upper vortex in the eastern and central tropical Atlantic and over this tropical wave. Should this tropical wave become better organized...I will consider upgrading it to a special feature with a tropical cyclone formation forecast. Regardless of development or not...this tropical wave could spread some of its northern squally weather (heavy rain with gusty winds) over the Republic of Cabo Verde in the next day or so.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0125Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...HURRICANE MATTHEW...
Current Prognosis...Once again...Matthew has strengthened rapidly as confirmed by aircraft reconaissance overnight and is already a category 2 hurricane with 100 mph maximum sustained winds. Nighttime infrared shows Matthew overall is a small to medium sized hurricane with a circular core of thunderstorms with a comma shaped curved band extending to the north and east of the circular core. Colorized infrared schemes show the western half of the core exhibits very strong thunderstorm activity with perhaps a pinhole eye developing as of 0900Z as the hurricane crosses 70W longitude. Earlier this morning at 0600Z the center of Matthew passed over 14N-69.5W. With atmospheric and thermodynamic conditions expected to become even more favorable in the coming days...Matthew in the next couple of days could become one of the strongest hurricanes in the Atlantic basin we have seen in the last few years.

Atmospheric Outlook for the Forecast Period...The westward-retrograding cut-off upper vortex in the eastern and central Atlantic has continued to push the upper anticyclone over Matthew in a westward direction...and it appears that the anticyclone has already caught up enough to Matthew such that the shear has reduced enough to allow Matthew to already rapidly strengthen into a decent hurricane. Matthew will be slowing down and then bending northward in track during the forecast period in response to the deep-layered 1011 mb frontal cyclone currently over the eastern United States. This will allow the upper anticyclone to further catch up and become vertically stacked with Matthew...potentially allowing Matthew to reach extrodinary strength while taking advantage of its low shear and enhanced upper outflow. It should be noted the northward turn is made initially very slow between 24 and 48 hours as it appears Matthew will be a bit too far south of the deep-layered frontal cyclonic system to be pulled in by it. But then the northward turn is made increasingly faster from 48 to 120 hours as Matthew is forecast to move closer to and get steered by a southern fracture upper trough to get left behind by the deep-layered frontal cyclonic system.

Thermodynamic Outlook for the Forecast Period...Matthew will be passing over rather favorable 30 to 31 deg C waters in the Caribbean in the next 96 hours...with an extremely favorable 32 deg C maximum located between Jamaica and Cuba possibly lying ahead in its path. Therefore additional rapid intensification of Matthew is possible...perhaps likely.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0600Z Oct 1)...125 mph maximum sustained wind hurricane centered in the south-central Caribbean Sea north of Colombia at 13.5N-74.1W

48 Hr Forecast (0600Z Oct 2)...150 mph maximum sustained wind hurricane in the central Caribbean Sea at 14.5N-75.5W

72 Hr Forecast (0600Z Oct 3)...160 mph maximum sustained wind hurricane just south-southeast of Jamaica at 16.5N-76.5W

96 Hr Forecast (0600Z Oct 4)...155 mph maximum sustained wind hurricane approaching the south coast of eastern Cuba at 19N-76.5W

120 Hr Forecast (0600Z Oct 5)...135 mph maximum sustained wind hurricane centered over the western Bahamas at 24N-76.5W

Track Forecast...Based on the 0600Z center fix in the above current prognosis...Matthew is a bit south and west of the previous forecast and satellite animation suggests some west-southwest wobbling is beginning as some of the computer models have been forecasting. Therefore I show some west-southwest tracking in the next 24 hours and have adjusted the track forecast a bit south and west overall when compared to the previous.

Intensity Forecast...I show further rapid intensification and put category 5 strength (160+ mph maximum sustained winds) on the table due to the rather favorable atmospheric and thermodynamic conditions Matthew will experience while moving into the central Caribbean Sea. Weakening is then shown by 96 to 120 hours due to land interaction with Jamaica and eastern Cuba.

Impact Forecast...Impact swath is an extrapolation of the 5 AM EDT NHC tropical storm wind field along my forecast track. On the current forecast track...the impact swath of tropical storm force winds does clip the north coast of Colombia where a tropical storm watch is in effect...and therefore some peripheral tropical storm conditions are possible in this area in the next 24 hours. Above all...interests in Jamaica...Haiti...and eastern Cuba...and Bahamas should begin thinking about preparing this weekend for what could be a severe strike from an intense Hurricane Matthew early next week...stay tuned.

2016 Atlantic Hurricane Season Birdseye Discussion #132

By: NCHurricane2009, 11:56 AM GMT on September 29, 2016

...THURSDAY SEPTEMBER 29 2016 8:00 AM EDT...
Alert! Interests in Jamaica...Haiti...and eastern Cuba...and Bahamas should begin thinking about preparations for early next week just after the weekend...for severe weather (highly damaging winds and flooding) from a possible major hurricane. Tropical wave Invest 97-L has rapidly strengthened into Tropical Storm Matthew while moving across the Lesser Antilles and into the eastern Caribbean Sea...and conditions could become extremely favorable for intensification this weekend before this system moves northward into these areas. See first special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on Matthew.

In addition to Matthew...see the following statements for three other areas of interest...

The following statment concerns area of interest #1 marked over the eastern and central tropical Atlantic in the atmospheric features chart below. A pair of tropical waves moving into the central tropical Atlantic are producing an east-west band of low-latitude thunderstorms while enhanced by upper divergence between the southwest side of a retrograding cut-off upper vortex and southeast side of the anticyclonic upper ridge currently pumped up by Matthew's thunderstorm latent heat release. The upper vortex is forecast to weaken...with the upper anticyclone over Matthew forecast to strengthen as Matthew itself strengthens. This will produce hostile northwesterly shear and upper convergence over this area of disturbed weather and therefore development is not expected. This is my final statement on this disturbance on this blog.

The following statement concerns area of interest #2 marked over the western Gulf of Mexico and east-central Mexico in the atmospheric features chart below. The tropical disturbance in this region has edged westward into Mexico and only a clump of thunderstorms remains. This is my final statment on this disturbance on this blog.

The following statement concerns area of interest #3 marked over the eastern tropical Atlantic in the atmospheric features chart below. The latest satellite pictures suggest a vigorous tropical wave has recently emerged from western Africa. Additional development is possible as the unfavorable cut-off upper vortex currently in the eastern Atlantic retrogrades westward and away while weakening...which will allow the development of a favorable upper ridge to the southeast of the upper vortex and over the tropical wave. Will consider upgrading the tropical wave to a special feature with a tropical cyclone formation forecast in my next blog update if the tropical wave continues to become better organized. Regardless of tropical cyclone formation or not...heavy rain with gusty winds will be possible over the Republic of Cabo Verde today and tomorrow.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0122Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM MATTHEW...
Current Prognosis...Over the last 24 hours...aircraft reconaissance confirmed that tropical wave Invest 97-L rapidly strengthened into strong Tropical Storm Matthew just before crossing the Lesser Antilles and into the eastern Caribbean Sea. Tropical storm conditions have quickly hit and now cleared the Lesser Antilles as Matthew advances further westward into the eastern Caribbean Sea this morning. The rapid strengthening has ceased and Matthew is currently parked at 65 mph maximum sustained winds due to the tropical storm encountering westerly vertical shear on the west side of the upper anticyclone that it was previously under. Infrared satellite animation shows the low-level cloud swirl of Matthew becoming exposed on the west side of its highly-organized circular thunderstorm mass as the storm runs into the shear. As of 0600Z earlier this morning...the center of Matthew passed over 14N-64W.

Atmospheric Outlook for the Forecast Period...Although the westward-retrograding cut-off upper vortex in the eastern Atlantic has continued to push the upper anticyclone over Matthew in a westward direction...Matthew's westward pace has exceeded the westward pace of the anitcyclone and Matthew is now dealing with an early episode of westerly shear that was not previously forecast. However Matthew will be slowing down and then bending northward in track later in the forecast period in response to the deep-layered 1010 mb frontal cyclone currently over the eastern United States. This will allow the upper anticyclone to catch up to Matthew...potentially allowing Matthew to again rapidly strengthen while again taking advantage of its low shear and enhanced upper outflow. It should be noted the northward turn is made initially very slow between 48 and 72 hours as it appears Matthew will be a bit too far south of the deep-layered frontal cyclonic system to be pulled in by it. But then the northward turn is made increasingly faster from 72 to 120 hours as Matthew is forecast to move closer and get steered by a southern fracture upper trough to get left behind by the deep-layered frontal cyclonic system. Just beyond the forecast period...conditions may get slightly less favorable for Matthew should it begin to encounter some westerly shear from the southern fracture upper trough. Other possiblities include Matthew's northward track eventually slowing down a couple of days after the 120-hour forecast period due to the strength of the surface ridge building behind the frontal cyclonic system.

Thermodynamic Outlook for the Forecast Period...Matthew will be passing over rather favorable 30 to 31 deg C waters during the entire forecast period. Therefore rapid intensification of Matthew is possible should atmospheric conditions become favorable.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0600Z Sep 30)...75 mph maximum sustained wind hurricane centered over the central Caribbean Sea at 14.5N-69W

48 Hr Forecast (0600Z Oct 1)...80 mph maximum sustained wind hurricane centered in the central Caribbean Sea south of Haiti at 15N-73.6W

72 Hr Forecast (0600Z Oct 2)...100 mph maximum sustained wind hurricane centered southeast of Jamaica and southwest of Haiti at 16N-75W

96 Hr Forecast (0600Z Oct 3)...120 mph maximum sustained wind hurricane centered between Jamiaca...Haiti...and eastern Cuba at 18N-76W

120 Hr Forecast (0600Z Oct 4)...120 mph maximum sustained wind hurricane centered over eastern Cuba at 20.5N-76W

Track Forecast...Based on the 0600Z center fix in the above current prognosis...Matthew is further west than the previous forecast and so the first 48 hours of the track forecast are adjusted accordingly. Also now that the center has become established...it is now clear that Matthew is moving with a less northward angle than I previously forecasted...and so the northward angle of the first 48 hours is reduced. This now means that my 48 hour position is too far south for Matthew to be strongly steered by the deep-layered frontal cyclone over the eastern US by that time...and so like the computer models have been doing I show an initial near-stall by 72 hours followed by an eventual northward acceleration by 96 hours and beyond. This brings the center of Matthew into eastern Cuba about one day later than I previously forecasted.

Intensity Forecast...Due to the early episode of shear noted in the above current prognosis...my intensity forecast for the first 48 hours is lower than the previous. However by 72 hours I show more intensification than previously forecast as the favorable upper anticyclone catches up to Matthew and reduces shear when Matthew slows down...and also because the delay in northward acceleration in the updated track forecast gives Matthew an extra day before it deals with land interaction with the northern Caribbean islands and possible westerly shear from the southern fracture upper trough mentioned in the above atmospheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 5 AM EDT NHC tropical storm wind field along my forecast track...with some slight growth of the swath shown in the later part of the forecast due to anticipated strengthening forecasted. The islands of Aruba...Bonaire...and Curacao offshore of northern South America are under a tropical storm watch but are not quiet in the impact swath for tropical storm force winds...but there are some model solutions that still show Matthew dipping a bit southward in track in which case tropical storm conditions would occur. Interests in Jamiaca...Haiti...and eastern Cuba...and Bahamas should begin thinking about preparations for early next week just after the weekend...for severe weather (highly damaging winds and flooding) from a possible major hurricane should the current forecast hold.

2016 Atlantic Hurricane Season Birdseye Discussion #131

By: NCHurricane2009, 5:41 AM GMT on September 28, 2016

...WEDNESDAY SEPTEMBER 28 2016 1:42 AM EDT...
Please note that the development of a significant hurricane in the Caribbean Sea is possible later this week. See the following statement for area of interest #1 and the special feature section below for more details...

The following statement concerns area of interest #1 marked over the central tropical Atlantic in the atmospheric features chart below. Vigorous tropical wave Invest 97-L has continued to become better organized. Meanwhile a southward-digging upper vortex in the east Atlantic is pushing the favorable anticyclonic upper ridging currently over this tropical wave in a westward direction such that it is staying collocated with the tropical wave. Combined with the rather warm waters in the Caribbean Sea...the development of a signficant hurricane is possible in the Caribbean in the next few days. Interests in the Lesser Antilles...the Virigin Islands...Puerto Rico...Haiti...the Dominican Republic...Jamaica...eastern Cuba...and Bahamas are urged to monitor this situation very carefully. Peripherial southern sea swells and heavy rain bands may also overspread the north coast of Venezula (and offshore islands) should this system develop into a strong tropical cyclone. See the special feature section below for more details.

The following statment concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. The tropical wave in this area is currently suppressed by westerly vertical shear and upper-level air being pushed southward toward this system which is shutting off poleward upper outflow...all courtesy of an eastern Atlantic cut-off upper vortex. However as this upper vortex weakens and retrogrades westward...some more favorable upper ridging will develop southeast of this upper vortex and possibly over the this tropical wave...and therefore will continue to watch this tropical wave in the coming days. Meanwhile an area of enhanced thunderstorms west of the tropical wave should not be confused with this tropical wave...and is being driven by upper divergence between the southwest side of the upper vortex and southeast side of the anticyclonic upper ridge currently over area of interest #1. Should this area of thunderstorms persist or become better organized...I will consider marking this as a seperate area of interest in my next blog post.

The following statement concerns area of interest #3 marked over the western Gulf of Mexico and eastern Mexico in the atmospheric features chart below. The surface low in this area has seen an increase in concentration and organization of its thunderstorm activity as the tail end of a cold front has overspread it and boosted its surface convergence...and while continuing to take advantage of lower shear and upper outflow from an upper ridge expanding from the southwest from the eastern Pacific. Currently this system is stalled in conflicting steering currents between the surface 997 mb frontal cyclone and upper trough over eastern North America to its northeast...and strong surface ridge building behind the frontal cyclone to its northwest. As the frontal cyclone moves away...the surface ridge is likely to slowly edge this system westward into eastern Mexico in the next 48 hours. Therefore although this system appears to have recently become better organized at 21.5N-97.5W...this location is already the east coast of Mexico and therefore land interaction will only increase as this system edges westward. Thus I have not upgraded this system to a special feature with a tropical cyclone formation forecast on this blog...but will continue to monitor this area for the formation of a short-lived tropical cyclone. Regardless of tropical cyclone formation or not...locally heavy rainfall and isolated flash flooding will be possible over east-central Mexico due to the slow-moving nature of this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1932Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 97-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...Tropical wave Invest 97-L in the central tropical Atlantic continues to become better organized while now featuring a small central dense overcast of thunderstorms and highly organized bands in the north half of the circulation. However aircraft reconaissance from this past afternoon found the surface circulation was not fully closed...and therefore Invest 97-L was not upgraded to a tropical cyclone. Satellite animation suggests the center of rotation passed over 13.5N-55W as of 0000Z earlier this evening. This is notably further north and east when compared to the previous forecast track...and therefore my updated forecast track listed below is adjusted north and east accordingly in the short-term. However the longer-term track forecast is adjusted more south and west due to changes in the forecast atmopsheric pattern...see atmospheric outlook section below for more details.

Atmospheric Outlook for the Forecast Period...The tropical wave has continued to become better organized while taking advantage of low shear and enhanced upper outflow beneath a large upper anticyclone. Meanwhile a cut-off upper vortex in the eastern Atlantic has continued to dive southward...and as a result the upper vortex is pushing the favorable anticyclone over this tropical wave in a westward direction such that it is staying collocated with the tropical wave. The track forecast continues to a show a slow down and then a bend to the north as this system moves into the central Caribbean Sea...due to the 997 mb frontal cyclone and upper trough currently over the eastern US and eastern Canada arriving into the west Atlantic. This weather system is shown stalling further west in the latest model runs and so the later part of the forecast track is shifted west and delays the bend to the north. The forecast strengthening rate is slowed after 48 hours...with some weakening shown by the end of the forecast...due to my forecast track taking this system into less favorable southwesterly vertical shear on the northwest side of the aforementioned upper anticyclone and due to forecast land interaction with the northern Caribbean Islands. It should be noted that I move this system sooner to the north compared to the lastest model runs...as I believe this system will be both far north enough and strong/tall enough to feel some steering influence from the upper trough associated with the aforementioned 997 mb frontal cyclone. I believe the latest model runs are initialized too far south based on the latest satellite organization...and therefore are preferring to stall this system before eventually moving it northward...perhaps due to the strength of the surface ridge building behind the frontal cyclone and the models having reduced interaction with the upper trough due to their further south initialization. However I do give some credence to the strength of the surface ridge building behind the frontal cyclone by showing only a slow northwest track by the end of the forecast. But if indeed this system takes longer to move north as the models show...I will have to adjust the later forecast points southward...perhaps with a higher intensity forecast as such a scenario would prevent or delay exposure to the westerly shear on the north side of the upper anticyclone.

Thermodynamic Outlook for the Forecast Period...This tropical wave will be passing over rather favorable 30 to 31 deg C waters during the entire forecast period. Coupled with the favorable atmospheric conditions through 48 hours mentioned above...the intensity forecast listed below shows brisk development of this system for the next 48 hours.

24 Hr Forecast (0000Z Sep 29)...45 mph maximum sustained wind tropical storm moving through the Lesser Antilles at 13.9N-61W

48 Hr Forecast (0000Z Sep 30)...70 mph maximum sustained wind tropical storm centered over the eastern Caribbean Sea at 16.4N-66W

72 Hr Forecast (0000Z Oct 1)...90 mph maximum sustained wind hurricane centered just south of Haiti and the Dominican Republic at 17.5N-71W

96 Hr Forecast (0000Z Oct 2)...100 mph maximum sustained wind hurricane centered between Haiti and eastern Cuba at 19N-74W

120 Hr Forecast (0000Z Oct 3)...80 mph maximum sustained wind hurricane centered over eastern Cuba at 20.5N-77W

2016 Atlantic Hurricane Season Birdseye Discussion #130

By: NCHurricane2009, 3:40 AM GMT on September 27, 2016

...MONDAY SEPTEMBER 26 2016 11:41 PM EDT...
Please note that the development of a significant hurricane in the Caribbean Sea is possible later this week. See the following statement for area of interest #2 and the special feature section below for more details...

The following statement concerns area of interest #1 marked in the northeast Atlantic in the atmospheric features chart below. Shortly after discussion #129 was released...and while moving beneath a more favorable upper ridge axis being pumped up by the warm air advection ahead of Karl's non-tropical remnant gale...the remnant low of Lisa re-generated significant thunderstorm activity and at one point the National Hurricane Center tropical weather outlook suggested the re-formation of tropical storm force winds. However their was not enough evidence to know if their was a closed circulation or not...and therefore Lisa was not re-upgraded to a tropical storm. In the next 24 hours while curving northeastward in track...Lisa's remnant will become absorbed by the cold front extending from Karl's remnant. This is my final statement on Lisa on this blog unless it continues to be mentioned in the National Hurricane Center tropical weather outlook.

The following statement concerns area of interest #2 marked over the central tropical Atlantic in the atmospheric features chart below. Vigorous tropical wave Invest 97-L has continued to become better organized. Meanwhile a southward-digging upper vortex in the east Atlantic is pushing the favorable anticyclonic upper ridging currently over this tropical wave in a westward direction such that it is staying collocated with the tropical wave. Combined with the rather warm waters in the Caribbean Sea...the development of a signficant hurricane is possible in the Caribbean in the next few days. Interests in the Lesser Antilles...the north coast of Venezula (and offshore islands)...Haiti...the Dominican Republic...Jamaica...eastern Cuba...and the eastern Bahamas are urged to monitor this situation very carefully. Peripherial northern and eastern sea swells and heavy rain bands may also overspread Puerto Rico and the Virgin Islands should this system develop into a signficant hurricane. See the special feature section below for more details.

The following statment concerns area of interest #3 marked over western Africa and the eastern tropical Atlantic in the atmospheric features chart below. A tropical wave is emerging from Africa and into the Atlantic tropics...but has lost thunderstorm activity in the process. It is not clear at this time if the cut-off upper vortex currently in the eastern tropical Atlantic will unfavorably shear this tropical wave...or if the tropical wave will develop beneath more favorable upper ridging to develop southeast of this upper vortex as the upper vortex begins to weaken. Therefore will continue to monitor this situation over the next few days as well.

The following statement concerns area of interest #4 marked just east of Florida in western Atlantic in the atmospheric features chart below. The surface trough supported by divergence on the southeast side of the upper vortex currently centered over the Florida panhandle has lifted northward from the western Bahamas while pulled by the 994 mb frontal cyclone moving into eastern North America. Additional development is not expected as the upper trough of the frontal cyclone will produce strong southwesterly upper winds likely to unfavorably shear this system. This is my final statement on this blog concerning this feature.

The following statement concerns area of interest #5 marked over the western Gulf of Mexico and southeastern Mexico in the atmospheric features chart below. A surface trough left behind by a tropical wave in the area has strengthened further into a 1010 mb surface low while taking advantage of lower shear and upper outflow from an upper ridge expanding from the southwest from the eastern Pacific. Currently this system is stalled in conflicting steering currents between the surface 994 mb frontal cyclone and upper trough over eastern North America to its northeast...and strong surface ridge building behind the frontal cyclone to its northwest. As the frontal cyclone moves away...the surface ridge is likely to slowly edge this system westward into eastern Mexico in the next 72 hours. Currently computer model support for this system is weak...and I also have not upgraded it to a special feature with a tropical cyclone formation forecast on this blog at this time because there are no signs of the thunderstorms organizing around the surface low...as thus far satellite animation shows the thunderstorm motion being dominated by the upper northwesterly anticyclonic flow on the northeast side of the upper ridge.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1927Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 97-L...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...Tropical wave Invest 97-L in the central tropical Atlantic continues to become better organized as the number of curved thunderstorm bands in the north half of the circulation continues to increase. The spin is also better defined in satellite animation...with the center of rotation passing over 11.5N-49.5W as of 0000Z. The position of the center is notably further north than yesterday and I have adjusted my forecast track listed below accordingly. I have also upped the intensity forecast due to the more quickly improving organization seen on satellite.

Atmospheric Outlook for the Forecast Period...The tropical wave has continued to become better organized while taking advantage of low shear and enhanced upper outflow beneath a large upper anticyclone. Meanwhile a cut-off upper vortex in the eastern Atlantic will continue to dive southward...and as a result the upper vortex is pushing the favorable anticyclone over this tropical wave in a westward direction such that it it staying collocated with the tropical wave. The track forecast continues to a show a slow down and then a bend to the north as this system moves into the central Caribbean Sea...due to the 994 mb frontal cyclone currently over the eastern US and eastern Canada arriving into the west Atlantic. I slow the strengthening rate by 72 to 96 hours...and then show weakening by 96 to 120 hours...due to my forecast track taking this system into less favorable westerly vertical shear on the north side of the aforementioned upper anticyclone and due to forecast land interaction with Haiti and the Dominican Republic. It should be noted that I move this system sooner to the north by 120 hours when compared to the lastest model runs...as I believe this system will be strong/tall enough to feel some steering influence from the upper trough associated with the aforementioned 994 mb frontal cyclone. It seems at this time the latest model runs mitigate the interaction with the upper trough...instead preferring to stall this system before eventually moving it northward...perhaps due to the strength of the surface ridge building behind the frontal cyclone? If indeed this system takes longer to move north...I will have to adjust the later part of my forecast to show a slower northward movement...perhaps with a higher intensity forecast as such a scenario would prevent or delay exposure to the westerly shear on the north side of the upper anticyclone.

Thermodynamic Outlook for the Forecast Period...This tropical wave will be passing over rather favorable 30 deg C waters during the entire forecast period. Coupled with the favorable atmospheric conditions through 72 hours mentioned above...the intensity forecast listed below shows brisk development of this system for the next 72 hours.

24 Hr Forecast (0000Z Sep 28)...Tropical low approaching the southern Lesser Antilles...centered at 11.8N-57.5W

48 Hr Forecast (0000Z Sep 29)...45 mph maximum sustained wind tropical storm centered over the southeastern Caribbean Sea at 12.2N-63.5W

72 Hr Forecast (0000Z Sep 30)...70 mph maximum sustained wind tropical storm centered over the eastern Caribbean Sea at 14.7N-68.5W

96 Hr Forecast (0000Z Oct 1)...90 mph maximum sustained wind hurricane centered just south of Haiti and the Dominican Republic at 17.2N-72.5W

120 Hr Forecast (0000Z Oct 2)...75 mph maximum sustained wind hurricane centered over Haiti at 19N-72.5W

2016 Atlantic Hurricane Season Birdseye Discussion #129

By: NCHurricane2009, 12:51 AM GMT on September 26, 2016

...SUNDAY SEPTEMBER 25 2016 8:52 PM EDT...
Please note that the development of a significant hurricane in the Caribbean Sea is possible later this week. See the following statement for area of interest #3 and the special feature section below for more details...

The following statement concerns area of interest #1 marked in the atmospheric features chart below. Tropical Storm Karl as expected has transitioned into a strong non-tropical gale while moving into the north-central Atlantic...as it has merged with the cold front of the 998 mb frontal cyclone emerging from Canada and as it has become supported by the divergence on the east side of the upper trough associated with the frontal cyclone. The remnant gale of Karl is expected to continue northeast into the northeastern Atlantic while combining with or becoming absorbed by the center of the 998 mb frontal cyclone. This is my final statement on Karl on this blog.

The following statement concerns area of interest #2 marked in the atmospheric features chart below. The remnant low of Lisa has not re-developed any significant thunderstorm activity while moving beneath a more favorable upper ridge axis being pumped up by the warm air advection ahead of Karl's non-tropical remnant gale. In the next 24 hours while curving northeastward in track...Lisa's remnant will become absorbed by the cold front extending from Karl's remnant. This is my final statement on Lisa on this blog.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. The organized tropical wave in this area has continued to become better organized and thus has been upgraded to tropical disturbance Invest 97-L. Meanwhile the upper troughing in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl will continue to amplify upper ridging into the north Atlantic...with the southward-digging upper vortex pushing the favorable anticyclonic upper ridging currently over this tropical wave in a westward direction such that it stays collocated with the tropical wave. Combined with the rather warm waters in the Caribbean Sea...the development of a signficant hurricane is possible in the Caribbean in the next few days. Interests across the Caribbean Sea are urged to carefully monitor the progress of this tropical wave over the next few days. See the special feature section below for more details.

The following statment concerns area of interest #4 marked over western Africa in the atmospheric features chart below. A tropical wave moving into western Africa has become better defined in satellite pictures as a large-sized concentration of strong thunderstorms. This tropical wave will emerge into the eastern tropical Atlantic in the next 48 hours. Meanwhile the upper troughing in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl continues to amplify upper ridging into the north Atlantic. It is not clear at this time if this upper vortex will unfavorably shear this tropical wave...or if the tropical wave will develop beneath more favorable upper ridging to develop southeast of this upper vortex. Therefore will continue to monitor this situation over the next few days as well.

The following statement concerns area of interest #5 marked over the western Bahamas and western Atlantic in the atmospheric features chart below. What is left of a decaying stalled frontal system and its upper trough over the eastern Unites States is a shrinking upper vortex currently centered over southern Alabama. Divergence on the southeast side of this upper vortex is producing a surface trough over the western Bahamas with shower and thunderstorm activity. However additional development is not likely as by 48 hours and beyond...this system will be accelerated north-norteastward by the 1000 mb frontal cyclone currently over the central US and central Canada...with the upper trough of this frontal cyclone producing strong southwesterly upper winds likely to unfavorably shear this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1327Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 97-L...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...The organized tropical wave in the central tropical Atlantic has continued to have an increase in curved thunderstorm bands...particularly on the north half of the system. The curvature in the thunderstorm activity and satellite animation suggest a center of surface low pressure is located at 9.5N-40.2W as of 0000Z this evening. Hovmoller Diagarams (http://www.nhc.noaa.gov/tafb_latest/gehov1latest. gif) suggest this tropical wave is progressing westward at a rate of 9W longitude per 24 hours.

Atmospheric Outlook for the Forecast Period...The tropical wave has continued to become better organized while taking advantage of low shear and enhanced upper outflow beneath a large upper anticyclone. Meanwhile the upper troughing in the northeast Atlantic is beginning to amplify into a southward-digging upper vortex as the remnant gale of Karl continues to amplify upper ridging into the north Atlantic. This southward-digging upper vortex will push the favorable anticyclone over this tropical wave in a westward direction such that it stays collocated with the tropical wave through the forecast period. The track forecast listed below at first is a continuation of the 9W longitude per 24 hour rate noted in the above current prongosis section. However later on the track forecast is slowed and bent increasingly to the north to be more in alignment with the latest computer model guidance. Presumably this change in track will be due to a low-level ridge weakness induced as the 1000 mb frontal cyclone currently over the central US and central Canada moves into the west Atlantic.

Thermodynamic Outlook for the Forecast Period...This tropical wave will be passing over rather favorable 29 to 30 deg C waters during the entire forecast period. Coupled with the favorable atmospheric conditions mentioned above...this is why the intensity forecast listed below shows the brisk development by the end of the forecast period.

24 Hr Forecast (0000Z Sep 27)...Tropical low centered at 9.8N-49.2W

48 Hr Forecast (0000Z Sep 28)...Tropical low approaching the southern Lesser Antilles...centered at 10.1N-57.2W

72 Hr Forecast (0000Z Sep 29)...35 mph maximum sustained wind tropical depression centered over the southeastern Caribbean Sea at 10.5N-63.2W

96 Hr Forecast (0000Z Sep 30)...60 mph maximum sustained wind tropical storm centered over the southeastern Caribbean Sea at 13N-68.2W

120 Hr Forecast (0000Z Oct 1)...80 mph maximum sustained wind hurricane centered over the central Caribbean Sea at 15.5N-72.2W

2016 Atlantic Hurricane Season Birdseye Discussion #128

By: NCHurricane2009, 5:42 AM GMT on September 25, 2016

...SUNDAY SEPTEMBER 25 2016 1:45 AM EDT...
Tropical Storm Karl is racing northeastward toward the north-central Atlantic and is expected to transition into a strong non-tropical gale affecting the Atlantic high seas in the next 24 hours. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

The following statement concerns area of interest #1 marked in the atmospheric features chart below. Although Lisa regained tropical storm status breifly this past morning...all thunderstorm activity since then has become sheared off and has dissipated and Lisa has just been downgraded to a remnant low. Lisa will continue northward into a more favorable lower shear environment beneath an upper ridge that has recently been pumped up by Karl's thunderstorm latent heat release and warm air advection ahead of the frontal system about to absorb Karl. However I have cancelled it as a special feature on this blog...but will consider re-upgrading it if it shows signs of re-generation. Regardless of re-generation or not...Lisa will become absorbed by the same frontal system absorbing Karl in 48 hours.

In addition to Karl and Lisa...see the following statements for two additional areas of interest...

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. The organized tropical wave in this area has regained thunderstorm activity as it moves into the central tropical Atlantic. Meanwhile the upper troughing in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl will continue to amplify upper ridging into the north Atlantic...with the southward-digging upper vortex pushing the favorable anticyclonic upper ridging currently over this tropical wave in a westward direction such that it stays collocated with the tropical wave. Computer model support continues to increase for this tropical wave...with the CMC...GFS...NAVGEM...and European (ECMWF) models all agreeing that this tropical wave will develop as it moves across the Caribbean Sea next week. I have not yet upgraded this tropical wave to a special feature with a 5-day tropical cyclone formation forecast as it appears this tropical wave is organizing at a far south latitude where it might in the short-term lack the coriolis effect that helps produce cyclonic rotation until it later reaches a more northward position. Also a more southward trajectory is increasing the likelihood that the wave becomes limited by land interaction with northern South America such that tropical cyclone formation might be more likely after 5 days when clears land and enters the south-central Caribbean.

The following statement concerns area of interest #3 marked over Africa in the atmospheric features chart below. Computer models suggest that a strong tropical wave will emerge from Africa and into the Atlantic tropics in about three days. Meanwhile the upper troughing in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl continues to amplify upper ridging into the north Atlantic. It is not clear at this time if this upper vortex will unfavorably shear this tropical wave...or if the tropical wave will develop beneath more favorable upper ridging to develop southeast of this upper vortex. Therefore will continue to monitor this situation over the next few days as well.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1935Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...While passing nearby and then pulling away from Bermuda...Karl has failed to strengthen in the last 24 hours due to increasing westerly vertical shear being applied by the amplifying upper trough entering the northwest Atlantic from eastern Canada. The shear has caused the once circular mass of thunderstorms over Karl's center to become elliptical in a southwest-northeast elongation...and the mass of thunderstorms is also becoming biased to the northeast of the center. As of 0000Z the center of Karl passed over 34N-59.5W.

Atmospheric Outlook for the Forecast Period...Karl will continue to accelerate northeastward while becoming pulled by the 996 mb frontal cyclone and its amplifying upper trough emerging from eastern Canada to its northwest. In the next 24 hours...Karl will transition into a powerful non-tropical remnant gale racing northeastward into the north-central Atlantic while becoming supported by divergence on the east side of the amplifying upper trough.

Thermodynamic Outlook for the Forecast Period...Karl is currently over favorable 28 deg C waters. However by 24 hours Karl will have crossed the 26 deg C isotherm and into cooler waters that will aid the transition to non-tropical mentioned at the end of the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 26)...Strong non-tropical remnant gale centered at 42.5N-41W

Track Forecast...Karl is following the previous track forecast line but is at a further southwest position along that line per the 0000Z center fix in the above current prognosis. Yet the 1800Z GFS computer model continues to show Karl going as far to the northeast as it forecasted yesterday. Therefore my updated forecast track is a compromise...showing Karl only slightly southwest of the 1800Z GFS for 24 hours.

Intensity Forecast...With Karl failing to strengthen in the last 24 hours...Karl remains on par with my previous intensity forecast and so I have made no changes.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track.

2016 Atlantic Hurricane Season Birdseye Discussion #127

By: NCHurricane2009, 9:25 AM GMT on September 24, 2016

...SATURDAY SEPTEMBER 24 2016 5:30 AM EDT...
Tropical Storm Karl's center to pass just southeast of Bermuda later this morning...tropical storm conditions are currently underway on the island. Weather conditions are to improve in Bermuda by this afternoon after Karl pulls away. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

Lisa weakens to a tropical depression under vertical shear while it continues northward across the open Atlantic. See second special feature section below for more details. Visit www.nhc.noaa.gov for up to the minute latest information on Lisa.

In addition to Karl and Lisa...see the following statements for two additional areas of interest...

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic in the atmospheric features chart below. The tropical wave which recently entered the eastern tropical Atlantic from Africa remains organized but has lost thunderstorm activity as it passes south of the Republic of Cabo Verde. However favorable anticyclonic upper ridging with low shear and enhanced upper outflow in the eastern tropical Atlantic...which aided in the formation of Lisa a few days ago...is forecast to persist. Moreover the the upper troughing in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl amplifies upper ridging into the north Atlantic...with the southward-digging upper vortex pushing the favorable eastern tropical Atlantic upper ridge westward such that it stays collocated with this tropical wave. Computer model support is increasing for this tropical wave...with the CMC...GFS...and NAVGEM models agreeing that this tropical wave will develop as it moves into the Caribbean Sea next week. Therefore will continue to monitor this tropical wave over the next few days.

The following statment concerns area of interest #2 marked over Africa in the atmospheric features chart below. Computer models suggest that a strong tropical wave will emerge from Africa and into the Atlantic tropics in about four days. Meanwhile the upper troughing in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl amplifies upper ridging into the north Atlantic. It is not clear at this time if this upper vortex will unfavorably shear this tropical wave...or if the tropical wave will develop beneath more favorable upper ridging to develop southeast of this upper vortex. Therefore will continue to monitor this situation over the next few days as well.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0123Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...As expected Karl has strengthened as it nears the island of Bermuda this early morning. Karl has the classic satellite appearance of a healthy and strong tropical storm featuring a large circular mass of thunderstorms with cirrus upper outflow clouds extending from the storm mass. As of 0600Z the center of Karl was just south of Bermuda at 31.2N-65W and was moving northeast such that the center will pass southeast of Bermuda later this morning. However the northern and western spiral bands of Karl are overspreading Bermuda with tropical storm conditions.

Atmospheric Outlook for the Forecast Period...Karl is beginning to accelerate northeastward while becoming pulled by the 1006 mb frontal cyclone and its amplifying upper trough emerging from eastern Canada to its north. Karl will transition into a powerful non-tropical remnant gale racing northeastward into the north-central Atlantic by 48 hours while becoming supported by divergence on the east side of the amplifying upper trough.

Thermodynamic Outlook for the Forecast Period...Karl is currently over favorable 29 to 30 deg C waters. However by the end of the 48-hour forecast period Karl will have crossed the 26 deg C isotherm and into cooler waters that will aid the transition to non-tropical mentioned at the end of the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0600Z Sep 25)...65 mph maximum sustained wind tropical storm centered at 36.5N-54W

48 Hr Forecast (0600Z Sep 26)...Strong non-tropical remnant gale centered at 46N-35W

Track Forecast...Karl is tracking slightly south of my previous track forecast...and so my updated forecast track is adjusted accordingly. By 48 hours my forecast track shows Karl notably further northeast than the previous forecasts. This is to keep up with the latest computer model guidance which shows Karl getting hurled into the north-central Atlantic at a faster pace.

Intensity Forecast...So far Karl is on par with my previous intensity forecast and so I have made no changes. I show no additional strengthening for the next 24 hours as the amplifying upper trough north of Karl should increase unfavorable westerly vertical shear across the tropical storm later today. Karl will then make the transition to non-tropical from high-end tropical storm strength...which means Karl's remnant will be a substantial non-tropical gale affecting the north Atlantic high seas.

Impact Forecast...Impact swath is an extrapolation of the 5 AM EDT NHC tropical storm wind field along my forecast track. Tropical storm conditions currently affecting Bermuda (rain bands with tropical storm force winds...as well as sea swells crashing ashore) should diminish later today once Karl pulls away.

...SPECIAL FEATURE...TROPICAL DEPRESSION LISA...
Current Prognosis...Under westerly vertical shear...Lisa has weakened to a tropical depression over the last 24 hours. However Lisa is hanging on as it produces a band of sheared off thunderstorms to the northeast of the swirl center. This band is currently oriented southwest-to-northeast...and at times there is a round strong of burst of thunderstorms at the southwest end of the band closest to the swirl center. As of 0600Z the center of Lisa was located at 23.8N-37.5W.

Atmospheric Outlook for the Forecast Period...Lisa continues on a northwestward track while influenced by both upper vorticity trying to drive it northward and 1026 mb surface ridge in the east Atlantic trying to drive it westward. The shear is due to the storm track not lining up with the southwesterly upper flow on the southeast side of the upper vorticity. In 24 hours however...Lisa will reach southeasterly flow on the northeast side of the upper vorticity better aligned with its track...likely resulting in reduced shear. The track forecast for 24 hours and beyond continues to be more northward due to a low-level ridge weakness created by Karl approaching from the west. At 48 hours...low-level southerly flow ahead of what is expected to be a non-tropical Karl will induce warm air advection and development of more favorable warm core upper ridging over Lisa...and so I show Lisa recovering a little bit during this time. By 48 hours the shear increases again as the upper trough associated with a non-tropical Karl approaches...and so I show weakening again. It is also likely that at 72 hours Lisa will become absorbed by the cold front driven by non-tropical Karl.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will be moving across a 27 deg C sea surface temp isotherm which will be warm enough to support Lisa tropically. A mass of dry air lies to the west of this tropical cyclone...due to upper convergence on the west side of the upper vorticity mentioned in the above atmospheric outlook section...and on the east side of a large upper anticyclone currently in the central Atlantic. The shear mentioned in the above current prongosis is pushing in this dry air which is only exacerbating the current disorganized state of Lisa.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0600Z Sep 25)...35 mph maximum sustained wind tropical depression centered at 26.5N-40W

48 Hr Forecast (0600Z Sep 26)...40 mph maximum sustained wind tropical storm centered at 31N-40.5W

72 Hr Forecast (0600Z Sep 27)...35 mph maximum sustained wind tropical depression becoming absorbed by cold front at 36N-37.5W

Track Forecast...Lisa is notably south and slightly east of the previous track forecast...and so I have adjusted my forecast track accordingly.

Intensity Forecast...Lisa is on par with the previous intensity forecast...no changes to make this early morning.

Impact Forecast...If Lisa follows the above intensity forecast...a small area of tropical storm force winds may re-develop near the storm center in 48 hours. The impact swath in the above forecast graphic depicts this scenario.

2016 Atlantic Hurricane Season Birdseye Discussion #126

By: NCHurricane2009, 4:45 AM GMT on September 23, 2016

...FRIDAY SEPTEMBER 23 2016 12:46 AM EDT...
Tropical Storm Karl strengthens and jumps northward in track such that its center will now pass over or close to the islands of Bermuda in the next 24 hours. A tropical storm warning for Bermuda has been raised this past afternoon for the strengthening tropical storm...and preparations in Bermuda should be completed by this upcoming morning. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

Tropical Storm Lisa is expected to weaken under vertical shear while it continues northward across the open Atlantic. See second special feature section below for more details. Visit www.nhc.noaa.gov for up to the minute latest information on Lisa.

In addition to Karl and Lisa...see the following statement for one additional area of interest...

The following statement concerns area of interest #1 marked over western Africa in the atmospheric features chart below. The tropical wave over western Africa has started to become better organized while it enters the eastern tropical Atlantic. Favorable anticyclonic upper ridging with low shear and enhanced upper outflow in the eastern tropical Atlantic...which aided in the formation of Tropical Storm Lisa a few days ago...is forecast to persist. Moreover the the upper trough that recently arrived in the northeast Atlantic is forecast to amplify into a southward-digging upper vortex as Karl amplifies upper ridging into the north Atlantic...with the southward-digging upper vortex pushing the favorable eastern tropical Atlantic upper ridge westward such that it stays collocated with this tropical wave. Computer model support is increasing for this tropical wave...with the CMC model suggesting this wave developing in the central tropical Atlantic...and the GFS computer model suggesting this wave developing as it approaches the eastern Caribbean Sea next week. If current organizational trends continue...I will consider upgrading this tropical wave to a special feature on this blog with a tropical cyclone formation forecast.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1928Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...The broad surface circulation of Karl appears to have jumped or regenerated northward in the last 24 hours beneath its canopy of organized spiral thunderstorm bands. Aircraft reconaissance confirmed that Karl has regained tropical storm status this past afternoon. As of 0000Z the center of the tropical storm was located at 27N-64W.

Atmospheric Outlook for the Forecast Period...Atmospheric conditions remain highly favorable for additional strengthening of Karl as Karl is collocated with a large central Atlantic upper anticyclone keeping shear low and enhancing the tropical storm's upper outflow. Karl continues on a northwestward track while pulled into a low-level ridge weakness in the western Atlantic created by the surface cold front and upper trough over the eastern United States (of note the remnants of Julia are along this front). The evolution of the leftover 1000 mb non-tropical low and upper trough over eastern Canada will affect the evolution of Karl from this point forward. This energy will become much more amplified in the next 24 hours...knocking out the 1021 mb ridge over the northeastern US coast and pulling Karl northward and eventually northeastward so that it passes over or very close to Bermuda in 24 to 48 hours. Karl will likely transition into a powerful non-tropical remnant gale racing northeastward into the north-central Atlantic by 72 hours while becoming supported by divergence on the east side of the amplifying upper trough.

Thermodynamic Outlook for the Forecast Period...Karl will be passing over rather favorable 30 deg C waters during the next 24 hours. By the end of the 72-hour forecast period...Karl will be approaching the 26 deg C isotherm and headed toward cooler waters...which will help the transition to non-tropical mentioned at the end of the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 24)...65 mph maximum sustained wind tropical storm centered just southwest of Bermuda at 31N-66W

48 Hr Forecast (0000Z Sep 25)...65 mph maximum sustained wind tropical storm centered at 34.5N-59.5W

72 Hr Forecast (0000Z Sep 26)...Strong non-tropical remnant gale centered at 42N-43.5W

Track Forecast...Per the 0000Z center fix in the current prognosis section...Karl is now notably more north and also slightly east of the prior forecast...and therefore I have adjusted my forecast accordingly. This now brings the center of Karl much closer to Bermuda than previously forecast.

Intensity Forecast...I have lowered the intensity forecast as Karl has taken its sweet time only slowly strengthening in the currently favorable environment. This environment is characterized by the large favorable upper anticyclone in the central Atlantic collolcated with Karl...which is helping keep shear favorably low and upper outflow favorably high...and the rather warm 30 deg C waters at the surface. Because aircraft reconaissance observations indicate the circulation is much better defined now and because these favorable conditions will persist for another 24 hours...I forecast Karl to briskly strengthen into a high-end tropical storm. I then show no additional strengthening from 24 to 48 hours due to increasing shear from the upper trough approaching Karl by that time per the above atmospheric outlook section. The above intensity forecast depicts Karl transitioning to non-tropical from high-end tropical storm strength...which means Karl's remnant will be a substantial non-tropical gale affecting the north Atlantic high seas should the current intensity forecast come to fruition.

Impact Forecast...Impact swath shows some expansion of the 11 PM EDT NHC tropical storm wind field along my forecast track in anticipation of Karl further strengthening. On the current forecast track which has Karl's center passing very close to Bermuda by 24 hours...strong tropical storm conditions are likely. A tropical storm warning was raised for Bermuda in the last 24 hours...and preparations for strong tropical storm conditions should be completed by this upcoming morning.

...SPECIAL FEATURE...TROPICAL STORM LISA...
Current Prognosis...Under westerly vertical shear...Lisa was essentially able to maintain strength over the last 24 hours while firing thunderstorm bursts near the center. However the most recent satellite frames suggest the thunderstorm activity is become well-removed from the center and therefore Lisa is likely to weaken in the next day or so. As of 0000Z the center of Lisa was located at 20.8N-35W.

Atmospheric Outlook for the Forecast Period...Lisa continues on a north-northwestward track while influenced by both an eastern Atlantic upper vortex trying to drive it northward and 1025 mb surface ridge in the east Atlantic trying to drive it westward. The shear is due to the storm track not lining up with the southwesterly upper flow on the southeast side of the upper vortex. In 48 hours however...Lisa will reach southeasterly flow on the northeast side of the upper vortex better aligned with its track...likely resulting in reduced shear. The track forecast for 48 hours and beyond continues to be more northward instead of westward around the north side of the upper vortex due to a low-level ridge weakness created by Karl approaching from the west. At 72 hours...low-level southerly flow ahead of what is expected to be a non-tropical Karl will induce warm air advection and development of more favorable warm core upper ridging over Lisa...and so I show Lisa recovering a little bit during this time. By 96 hours the shear increases again as the upper trough associated with a non-tropical Karl approaches...and so I show weakening again. It is also likely that at 96 hours Lisa will become absorbed by the cold front extending from non-tropical Karl.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will be moving across a 27 deg C sea surface temp isotherm which will be warm enough to support Lisa tropically. A mass of dry air lies to the west of this tropical cyclone...due to upper convergence on the west side of the east Atlantic upper vortex mentioned in the above atmospheric outlook section...and on the east side of a large upper anticyclone currently in the central Atlantic. The shear mentioned in the above current prongosis is pushing in this dry air which is only exacerbating the current disorganizational trend noted in the above current prognosis section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 24)...35 mph maximum sustained wind tropical depression centered at 24.5N-37.5W

48 Hr Forecast (0000Z Sep 25)...35 mph maximum sustained wind tropical depression centered at 27.5N-40W

72 Hr Forecast (0000Z Sep 26)...40 mph maximum sustained wind tropical storm centered at 31.5N-41W

96 Hr Forecast (0000Z Sep 27)...35 mph maximum sustained wind tropical depression becoming absorbed by cold front at 36.5N-39W

Track Forecast...No changes to the track forecast as Lisa remains essentially on the prior forecast per the above current prognosis 0000Z center fix.

Intensity Forecast...The intensity forecast is slightly raised when compared to the previous as Lisa has been holding on to low-end tropical storm strength per the above current prognosis section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with the swath absent along the portion of the forecast where Lisa is expected to be below tropical storm force.

2016 Atlantic Hurricane Season Birdseye Discussion #125

By: NCHurricane2009, 3:21 AM GMT on September 22, 2016

...WEDNESDAY SEPTEMBER 21 2016 11:25 PM EDT...
Tropical Storm Karl weakens to a tropical depression while continuing to deal with nearby upper vorticity. However this upper vorticity has finally begun dissipating and Karl is quickly recovering its organization on satellite pictures...a sign Karl could strengthen briskly and develop into a hurricane as it moves into warmer waters and more favorable atmospheric conditions. Karl is likely to bring tropical storm conditions in about 2 to 3 days to the island of Bermuda while the center passes nearby. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

While moving northward into the open Atlantic...Lisa already begins weakening under vertical shear ahead of schedule. See second special feature section below for more details. Visit www.nhc.noaa.gov for up to the minute latest information on Lisa.

In addition to Karl and Lisa...see the following statements for two other areas of interest...

The following statement concerns area of interest #1 marked in the southern Caribbean Sea in the atmospheric features chart below. A large area of showers and thunderstorms has developed while a surface tropical wave moving westward in the region interacts with split flow upper divergence between the south side of the large upper vortex currently in the Caribbean Sea and east side of an upper ridge over the eastern Pacific Ocean. This tropical wave is not expected to develop in the Caribbean as it makes landfall in Central America shortly...afterwards moving into the the eastern Pacific. This is my first and also final statement on this disturbed weather on this blog.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. The tropical wave over western Africa has not become better organized while it begins to enter the eastern tropical Atlantic. However...favorable anticyclonic upper ridging with low shear and enhanced upper outflow in the eastern tropical Atlantic...which has recently aided in the formation of Tropical Storm Lisa...is forecast to persist. Therefore will continue to monitor the progress of this tropical wave. At this time...no computer models show this tropical wave developing.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1928Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL DEPRESSION KARL...
Current Prognosis...This past morning and afteroon...Karl weakened further to a tropical depression featuring a disorganized surface circulation on visible satellite pictures that was de-coupled from its thunderstorm activity lying behing to the east. This was due to the persistent upper vortex that has been near the northern Lesser Antilles which was suppressing thunderstorm activity over Karl's west half. At one point earlier today the National Hurricane Center wasn't sure if Karl lost its closed circulation or not as aircraft reconaissance struggled to find one. This late afternoon and evening however...the upper vortex has essentially diminished and Karl is already quickly repsonding to the more favorable environment. The thunderstorm activity that was lagging behind to the east has significantly expanded while catching up to and covering the surface circulation...while strengthening and becoming better organized with spiral banding features. As of 1800Z the National Hurricane Center 5 PM EDT advisory suggested the surface circulation was at 21.9N-58.7W...and this surface circulation was somewhat discernable in visible satellite. However as the sun has set over Karl...it was a little more challenging with the infrared to spot the low-level clouds beneath the cirrus upper outflow clouds of the aforementioned thunderstorm activity spreading in from the east...but my guess is that the center was near or at 22N-59.5W as of 0000Z.

Atmospheric Outlook for the Forecast Period...Atmospheric conditions are becoming more favorable for Karl to develop as the nearby upper vortex near the northern Lesser Antilles is finally dissipating...with the large favorble central Atlantic upper anticyclone growing and beginning to collocate with Karl. The track of Karl on cue has developed a more northward angle in response to a low-level ridge weakness in the western Atlantic created by the surface cold front and upper trough over the eastern United States (of note the remnants of Julia are along this front). The evolution of the 992 mb frontal cyclone and its upper trough currently over eastern Canada will affect the evolution of Karl from 48 to 96hours. A seperate new 1000 mb frontal cyclone has formed to the east where divergence along the east side of the upper trough is maximum...and this new frontal cyclone will produce its own cold air advection and thus its own upper trough while moving into the north Atlantic (however these features will not be enough to recurve Karl in the next 24 hours as the 1025 mb ridge currently over the eastern US moves into the west Atlantic and blocks the recurvature). Meanwhile the original 992 mb frontal cyclone/upper trough energy will become much more amplified by 48 hours...knocking out the aforementioned 1025 mb ridge...and pulling Karl northward and northeastward so that it passes near the island of Bermuda by 48 to 72 hours. Karl will likely transition into a powerful non-tropical remnant gale racing northeastward into the north-central Atlantic by 96 hours while becoming supported by divergence on the east side of the amplifying upper trough.

Thermodynamic Outlook for the Forecast Period...Karl will be passing over rather favorable 30 to 31 deg C waters during the next 48 hours. By the end of the 96-hour forecast period...Karl will be approaching the 26 deg C isotherm and headed toward cooler waters...which will help the transition to non-tropical mentioned at the end of the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 23)...60 mph maximum sustained wind tropical storm centered at 24N-65W

48 Hr Forecast (0000Z Sep 24)...85 mph maximum sustained wind hurricane centered just southwest of Bermuda at 28N-67W

72 Hr Forecast (0000Z Sep 25)...75 mph maximum sustained wind hurricane centered east-northeast of Bermuda at 33.5N-60.5W

96 Hr Forecast (0000Z Sep 26)...Strong non-tropical remnant gale centered at 40N-47.5W

Track Forecast...No changes to the track forecast as Karl remains essentially on the prior forecast per the above current prognosis 0000Z center fix.

Intensity Forecast...Even though Karl is currently weaker than the previous intensity forecast...I only have lowered the intensity forecast for 24 hours and catch up to the previous intensity forecast by 48 hours and onwards as Karl per the above current prognosis is showing quick signs of organization while moving into a rather favorable environment. This environment is characterized by the large favorable upper anticyclone in the central Atlantic expanding and collocating with Karl which will help keep shear favorably low and upper outflow favorably high...and the rather warm 30 to 31 deg C waters Karl is moving into tonight. Weakening is shown by 72 hours due to increasing shear from the upper trough approaching Karl by that time per the above atmospheric outlook section. The above intensity forecast depicts Karl transitioning to non-tropical from hurricane strength...which means Karl's remnant will be a substantial non-tropical gale affecting the north Atlantic high seas should the current intensity forecast come to fruition.

Impact Forecast...Impact swath shows re-development and expansion of a tropical storm wind field along my forecast track in anticipation of Karl potentially re-strengthening briskly. On the current forecast track which has Karl's center passing just southeast of Bermuda in 3 to 4 days...tropical storm conditions are likely. Any northwest shift in the forecast track could mean hurricane conditions for Bermuda...that is if Karl strengthens as forecast.

...SPECIAL FEATURE...TROPICAL STORM LISA...
Current Prognosis...The hunch that Lisa was starting to get sheared during last night's current prognosis turned out correct...and now Lisa is weakening tonight after reaching a peak of 50 mph maximum sustained winds earlier today. Like a typical tropical storm that gets sheared...the organized thunderstorms and mid-level center have become displaced eastward from the surface center on satellite pictures...and now the thunderstorms are losing their organization. As of 0000Z the center of Lisa was located at 19N-32.8W.

Atmospheric Outlook for the Forecast Period...The eastern Atlantic upper trough that is shearing Lisa has recently amplified further into an upper vortex that will soon retrograde southwestward. Lisa continues on a north-northwestward track while influenced by both the upper vortex trying to drive it northward and 1023 mb surface ridge in the east Atlantic trying to drive it westward. The shear is due to the storm track not lining up with the southwesterly upper flow on the southeast side of the upper vortex. In 72 hours however...Lisa will reach southeasterly flow on the northeast side of the upper vortex better aligned with its track...likely resulting in reduced shear. The track forecast for 72 hours and beyond continues to be more northward instead of westward around the north side of the upper vortex due to a low-level ridge weakness created by Karl approaching from the west. At 96 hours...low-level southerly flow ahead of what is expected to be a non-tropical Karl will induce warm air advection and development of more favorable warm core upper ridging over Lisa...and so I show Lisa recovering a little bit during this time. By 120 hours the shear increases again as the upper trough associated with a non-tropical Karl approaches...and so my forecast recovery remains slight. It is also likely that at 120 hours Lisa will become absorbed by the cold front extending from non-tropical Karl.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will be moving across a 27 deg C sea surface temp isotherm which will be warm enough to support Lisa tropically. A mass of dry air lies to the west of this tropical cyclone...due to upper convergence on the west side of the east Atlantic upper trough mentioned in the above atmospheric outlook section...and on the east side of a large upper anticyclone currently in the central Atlantic. The shear mentioned in the above current prongosis is pushing in this dry air which is only exacerbating the current weakening of this system.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 23)...35 mph maximum sustained wind tropical depression centered at 21.5N-35W

48 Hr Forecast (0000Z Sep 24)...Remnant low centered at 24.5N-37.5W

72 Hr Forecast (0000Z Sep 25)...Remnant low centered at 27.5N-40W

96 Hr Forecast (0000Z Sep 26)...30 mph maximum sustained wind tropical depression centered at 31.5N-41W

120 Hr Forecast (0000Z Sep 27)...35 mph maximum sustained wind tropical depression becoming absorbed by cold front at 36.5N-39W

Track Forecast...No changes to the track forecast as Lisa remains essentially on the prior forecast per the above current prognosis 0000Z center fix.

Intensity Forecast...I have lowered the intensity forecast as Lisa is getting sheared and weakening ahead of schedule. Therefore Lisa is now likely to become a remnant low by 48 hours. However I still show a forecast through 120 hours as I forecast this system to re-develop a little in a more favorable atmopsheric environment in 72 to 120 hours (see above atmospheric outlook section for more details).

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with the swath absent along the portion of the forecast where Lisa is expected to be below tropical storm force.

2016 Atlantic Hurricane Season Birdseye Discussion #124

By: NCHurricane2009, 4:50 AM GMT on September 21, 2016

...WEDNESDAY SEPTEMBER 21 2016 12:51 AM EDT...
Tropical Storm Karl weakens and struggles again while continuing to deal with nearby upper vorticity. However Karl could strengthen briskly and develop into a hurricane while moving into warmer waters and more favorable atmospheric conditions over the next few days. Karl is likely to bring tropical storm conditions in about 3 to 4 days to the island of Bermuda while the center passes nearby. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

Tropical depression thirteen in the eastern tropical Atlantic strengthens further into Tropical Storm Lisa. Lisa is only expected to be a marine threat while curving northward into the open Atlantic over the next few days...see second special feature section below for more details. Visit www.nhc.noaa.gov for up to the minute latest information on Lisa.

In addition to Karl and Lisa...see the following statements for two other areas of interest...

The following statement concerns area of interest #1 marked in the western Atlantic just over and just south of Bermuda in the atmospheric features chart below. The surface trough in this area has not developed further...and without a closed circulation will be exposed to the approach of Karl from the south...with Karl stealing all low-level inflow. Moreover the window of time for this system to tropically develop is now only 48 hours before the upper trough currently moving into eastern Canada approaches and amplified over it...which will cause this surface trough to transition into a non-tropical frontal low. With tropical cyclone formation unlikely...this is my final statement on this feature on this blog.

The following statement concerns area of interest #2 marked over Africa in the atmospheric features chart below. The tropical wave that was over central Africa last night has become weaker on satellite pictures while moving into western Africa tonight. However...favorable anticyclonic upper ridging with low shear and enhanced upper outflow in the eastern tropical Atlantic...which has recently aided in the formation of Tropical Storm Lisa...is forecast to persist as this tropical wave approaches and then enters the Atlantic from Africa in the next couple of days. Therefore will continue to monitor the progress of this tropical wave. At this time...no computer models show this tropical wave developing.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1928Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...As Karl has moved westard into the upper vortex that has been lingering near the northern Lesser Antilles...it has become less organized and has weakened back to a minimal tropical storm. The strongest thunderstorm activity is biased well east of Karl's swirl center as the upper vortex is blocking the western upper outflow of the tropical storm. As of 0000Z the center of Karl passed over 20N-55.8W.

Atmospheric Outlook for the Forecast Period...In the next few days...atmospheric conditions are still expected to become more conducive for additional development of Karl as the nearby upper vortex mentioned in the above current prognosis diminishes. This will allow the large favorble central Atlantic upper anticyclone to grow and stay collocated with Karl. The track of Karl is expected to develop a more northward angle in the next 24 hours as Karl moves into the low-level ridge weakness in the western Atlantic created by the surface cold front and upper vortex over the eastern United States (of note the remnants of Julia are along this front). The evolution of the frontal cyclone and its upper trough currently moving into eastern Canada will affect the evolution of Karl from 72 to 120 hours. A seperate new frontal cyclone is expected to form where the cold...warm...and occluded fronts intersect...with the new frontal cyclone creating its own upper trough and moving into the north Atlantic (however these features will not be enough to recurve Karl as the 1022 mb ridge currently over the eastern US moves into the west Atlantic and blocks the recurvature). Meanwhile the original frontal cyclone/upper trough energy will become much more amplified by 72 hours...knocking out the aforementioned 1022 mb ridge...and pulling Karl northward and northeastward so that it passes either near or over the island of Bermuda by 72 to 96 hours. Karl will likely transition into a powerful non-tropical remnant gale racing northeastward into the north-central Atlantic by 120 hours while becoming supported by divergence on the east side of the amplifying upper trough.

Thermodynamic Outlook for the Forecast Period...Karl will be passing over rather favorable 29 to 31 deg C waters during the next 72 hours. By the end of the 120-hour forecast period...Karl will be approaching the 26 deg C isotherm and headed toward cooler waters...which will help the transition to non-tropical mentioned at the end of the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 22)...45 mph maximum sustained wind tropical storm centered at 22.5N-60W

48 Hr Forecast (0000Z Sep 23)...65 mph maximum sustained wind tropical storm centered at 24N-65W

72 Hr Forecast (0000Z Sep 24)...85 mph maximum sustained wind hurricane centered just southwest of Bermuda at 28N-67W

96 Hr Forecast (0000Z Sep 25)...75 mph maximum sustained wind hurricane centered east-northeast of Bermuda at 33.5N-60.5W

120 Hr Forecast (0000Z Sep 26)...Strong non-tropical remnant gale centered at 40N-47.5W

Track Forecast...No changes to the track forecast as Karl remains essentially on the prior forecast per the above current prognosis 0000Z center fix.

Intensity Forecast...I have reverted back to the weaker intensity forecast from discussion #122...which accounted for Karl struggling with the nearby upper vorticity as Karl is currently doing. However even this forecast still shows brisk strengthening for the timeframe that is now at 48 to 72 hours as the latest upper wind forecast still shows the large favorable upper anticyclone in the central Atlantic expanding and staying collocated with Karl which will help keep shear favorably low and upper outflow favorably high...and due to the very favorable 30 to 31 deg C waters Karl will be over by that time. Weakening is shown by 96 hours due to increasing shear from the upper trough approaching Karl by that time per the above atmospheric outlook section. The above intensity forecast depicts Karl transitioning to non-tropical from hurricane strength...which means Karl's remnant will be a substantial non-tropical gale affecting the north Atlantic high seas should the current intensity forecast come to fruition.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with growth of the swath where Karl is still forecast to strengthen. On the current forecast track which has Karl's center passing just southeast of Bermuda in 3 to 4 days...tropical storm conditions are likely. Any northwest shift in the forecast track could mean hurricane conditions for Bermuda...that is if Karl strengthens as forecast.

...SPECIAL FEATURE...TROPICAL STORM LISA...
Current Prognosis...Tropical depression thirteen has continued to become better organized and stronger while west of the Republic of Cabo Verde...and now is Tropical Storm Lisa. The satellite appearance of this system is that of a classic healthy tropical storm...with a large comma-shaped central storm mass and some outer skeletal bands to the south. However the central storm mass is a bit lopsided to the east of the center...perhaps as some westerly vertical shear from the upper trough that has moved into the eastern Atlantic begins affecting Lisa. As of 0000Z the center of Lisa was located at 16.8N-31.5W.

Atmospheric Outlook for the Forecast Period...Lisa is tracking more north and less west than prior track forecasts suggested...indicating Lisa is already a strong and tall enough tropical cyclone to be influenced track-wise by the upper that has recently moved into the eastern Atlantic. After 24 hours...Lisa will have moved into shearing southwesterly flow on the east side of this upper trough which will cause Lisa to begin weakening. By 96 hours...the upper trough will have cut-off into a southwestward-retrograding upper vortex...with this system likely to be located beneath the northeast side of this feature. Southeastery flow on the northeast side of the upper vortex will be more in alignment with the forecast northwest track which should reduce the shear. The track forecast for 96 and 120 hours will likely continue to be more northward instead of westward around the north side of the upper vortex due to a low-level ridge weakness created by Karl approaching from the west. By 120 hours...low-level southerly flow ahead of what is expected to be a non-tropical Karl will induce warm air advection and perhaps the development of more favorable warm core upper ridging over Lisa...and so I show Lisa recovering a little bit at the end of the forecast period.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will be moving across a 27 deg C sea surface temp isotherm which will be warm enough to support Lisa tropically. A mass of dry air lies to the west of this tropical cyclone...due to upper convergence on the west side of the east Atlantic upper trough mentioned in the above atmospheric outlook section...and on the east side of a large upper anticyclone currently in the central Atlantic. As long as shear remains low...this tropical cyclone will be able to ward off this dry air by producing thunderstorms stacked with the circulation. However by 48 hours and beyond when the shear is forecast to increase...the shear may waft in this dry air which could exacerbate the weakening of this system.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 22)...65 mph maximum sustained wind tropical storm centered at 19N-33W

48 Hr Forecast (0000Z Sep 23)...50 mph maximum sustained wind tropical storm centered at 21.5N-35W

72 Hr Forecast (0000Z Sep 24)...35 mph maximum sustained wind tropical depression centered at 24.5N-37.5W

96 Hr Forecast (0000Z Sep 25)...35 mph maximum sustained wind tropical depression centered at 27.5N-40W

120 Hr Forecast (0000Z Sep 26)...40 mph maximum sustained wind tropical storm centered at 31.5N-41W

Track Forecast...Per the above atmospheric outlook section...Lisa is tracking at a more northward angle and thus my updated track forecast is adjusted eastward.

Intensity Forecast...I have slightly lowered the intensity forecast as Lisa is slightly below the previous forecast...but the updated intensity forecast still shows Lisa strengthening to a strong tropical storm in the next 24 hours. Weakening is then shown by 48 to 72 hours when the shear increases per the above atmospheric outlook section. Weakening is stopped by 96 and 120 hours when this system reaches a lower shear environment also per the above atmospheric outlook.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with the swath width maximum where I forecast Lisa to reach peak strength..and then a tapering off of the swath to reflect the subsequent forecast weakening.

2016 Atlantic Hurricane Season Birdseye Discussion #123

By: NCHurricane2009, 8:15 AM GMT on September 20, 2016

**This blog post was intended to be posted by 2 or 3 AM EDT this morning. However failure of my wireless modem at home created technical difficulties in accessing the internet...resulting in this post getting uploaded just after 4 AM EDT via an ethernet connection I was finally able to make through the modem. The track and intensity forecast graphics for Karl and tropical depression thirteen were not created due to difficulties in internet access**

...TUESDAY SEPTEMBER 20 2016 4:15 AM EDT...
Tropical Storm Karl has begun strengthening while moving across the central tropical Atlantic. Karl could strengthen more rapidly into a strong hurricane while moving into warmer waters and even more favorable atmospheric conditions over the next few days. Changes in the computer model runs regarding the evolution of the frontal cyclone currently over central Canada have resulted in a northward shift in the track forecast...and Karl could strike Bermuda as a strong hurricane in 4 to 5 days. Intersts in Bermuda should carefully monitor Karl and begin thinking about preparations if the current forecast holds. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

The vigorous tropical wave in the eastern tropical Atlantic strengthens into the thirteenth tropical depression of the 2016 Atlantic hurricane season...and is forecast to strengthen further into a tropical storm. This system is expected to curve northward into the open Atlantic over the next few days...see second special feature section below for more details. Visit www.nhc.noaa.gov for up to the minute latest information on this tropical cyclone.

In addition to Karl and tropical depression thirteen...see the following statements for two other areas of interest...

The following statement concerns area of interest #1 marked in the western Atlantic just south of Bermuda in the atmospheric features chart below. Over the last few days...what was left of the tropical wave that produced Tropical Storm Ian has migrated northwestward to the waters south of Bermuda while becoming absorbed by the cold front that Ian drove southward when Ian transitioned to non-tropical. This front is beginning to decay into a surface trough...with the tail end of this surface trough producing organized thunderstorm activity to the south of Bermuda this past afternoon while a favorable anticyclonic upper ridge expands over it from the south. Over the next 72 hours...this surface trough is likely to continue northwestward into the waters offshore of the northeastern United States while steered by the 1031 mb ridge in the northeast Atlantic...after which time it will transition into a northeastward tracking non-tropical remnant gale as the upper trough currently over central Canada approaches and amplifies over it. Will watch for signs of additional tropical development from this system over the next 72 hours as the favorable upper ridge will continue to expand over this system from the south.

The following statement concerns area of interest #2 marked over Africa in the atmospheric features chart below. A tropical wave is becoming better defined and stronger in satellite pictures over central Africa. Favorable anticyclonic upper ridging with low shear and enhanced upper outflow in the eastern tropical Atlantic...which has recently aided in the formation of tropical depression thirteen...is forecast to persist as this tropical wave approaches and then enters the Atlantic from Africa in the next few days. Therefore will continue to monitor the progress of this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...It appears that as Karl is approaching warmer 29 deg C waters...it has tapped into enough instability to finally fire some strong thunderstorm activity to overcome the effects of dry air and nearby upper vorticity. As a result Karl has finally begun to strengthen. However thunderstorm activity remains lopsided to the northeast of the surface center...this time due to southerly vertical shear from the upper vortex that has been hanging around 57.5W longitude over the last few days. As of 0000Z the center of Karl passed over 19.5N-50.5W.

Atmospheric Outlook for the Forecast Period...In the next few days...atmospheric conditions are expected to become more conducive for additional development of Karl as the upper vortex currently near 57.5W longitude is expected to dissipate...which will allow the large favorble central Atlantic upper anticyclone to grow and stay collocated with Karl. The track of Karl is expected to have a more northward angle after 24 hours as Karl moves into the low-level ridge weakness in the western Atlantic created by the arrival of a dissipating frontal cyclone and upper trough recently arriving into the eastern US (of note the remnants of Julia have become entagled in that system). There have been some notable changes in the computer models regarding the evolution of the stronger frontal cyclone and its upper trough currently over central Canada that have ramifications in how Karl evolves. Like before...the models show a seperate new frontal cyclone forming where the cold...warm...and occluded fronts intersect...with the new frontal cyclone creating its own upper trough and moving into the north Atlantic (however these features will not be enough to recurve Karl as the 1019 mb ridge currently over the eastern US moves into the west Atlantic and blocks the recurvature). The big change with the models is how the original frontal cyclone/upper trough energy evolves while moving into eastern Canada and the northwest Atlantic...with the models now showing this upper trough energy become much more amplified...knocking out the aforementioned 1019 mb ridge...and pulling Karl northward and northeastward either near or over the island of Bermuda by 96 to 120 hours. The only good news for Bermuda then is increasing shear from the amplifying upper trough may prevent additional strengthening of Karl as it passes over or near Bermuda.

Thermodynamic Outlook for the Forecast Period...Karl will be passing over 28 to 31 deg C waters on the updated forecast track during the 120-hour forecast period. Therefore water temps will support Karl as a tropical cyclone during the duration of the forecast period.

**Forecast graphic not available tonight due to difficulties in personal internet access**

24 Hr Forecast (0000Z Sep 21)...50 mph maximum sustained wind tropical storm centered at 20.5N-56W

48 Hr Forecast (0000Z Sep 22)...65 mph maximum sustained wind tropical storm centered at 22.5N-60W

72 Hr Forecast (0000Z Sep 23)...85 mph maximum sustained wind hurricane centered at at 24N-65W

96 Hr Forecast (0000Z Sep 24)...105 mph maximum sustained wind hurricane centered just southwest of Bermuda at 28N-67W

120 Hr Forecast (0000Z Sep 25)...100 mph maximum sustained wind hurricane centered east-northeast of Bermuda at 33.5N-60.5W

Track Forecast...The track forecast is adjusted slightly northward in the short-term due to the 0000Z position in the above current prognosis being slightly north of the prior track forecast. The track forecast is then significantly adjusted northward for 0000Z September 24 and onwards due to changes with how the computer models handle the frontal cyclone over central Canada per the above atmospheric outlook section. This means the island of Bermuda could be struck by what could be a rather strong Hurricane Karl in 96 to 120 hours...and interests in Bermuda should begin thinking about preparations for Karl.

Intensity Forecast...I have raised the intensity forecast for Karl as the tropical storm is already beginning to overcome the unfavorable dry air and nearby upper vorticity. Brisk strengthening is shown from 48 to 96 hours as the latest upper wind forecast still shows the large favorable upper anticyclone in the central Atlantic expanding and staying collocated with Karl which will help keep shear favorably low and upper outflow favorably high...and due to the very favorable 30 to 31 deg C waters Karl will be over by that time. Weakening is shown by 120 hours due to increasing shear from the upper trough approaching Karl by that time per the above current prognosis.

Impact Forecast...Sea swells and rough seas are expected in the storm and storm vicinity over the next few days...with swells reaching the shores of the northern Caribbean Islands...Bahamas...and Bermuda later this week. Bermuda could be struck by tropical storm conditions in 4 to 5 days...with hurricane force conditions possible if both the anticipated strengthening occurs and the center of Karl passes close enough to the island.

...SPECIAL FEATURE...TROPICAL DEPRESSION THIRTEEN...
Current Prognosis...The vigorous tropical wave in the eastern tropical Atlantic has continued to become better organized at a location just southwest of the Republic of Cabo Verde and is now the thirteenth tropical depression of the 2016 Atlantic Hurricane Season. As of 0000Z the center of the new tropical depression was located at 14N-29W.

Atmospheric Outlook for the Forecast Period...As Karl strengthens while moving toward the west Atlantic in the coming days...latent heat release of its thunderstorm activity is likely to pump up a warm core upper anticyclone currently in the central Atlantic...which should cause the upper trough that has recently moved into the northeast Atlantic to dive southeastward around the east side of this anticyclone and toward this system. This upper trough is likely to bend the track northward and begin unfavorably shearing this system by the later part of the forecast period. By the end of the 120-hour forecast period...the upper trough will have cut-off into a southwestward-retrograding cut-off upper vortex...with this system likely to be located beneath the northeast side of this feature. Southeasterly flow on the northeast side of the upper vortex will be more in alignment with the forecast northwest track which should reduce the shear. The track forecast will likely continue northwestward instead of more westward around the north side of the upper vortex due to a low-level ridge weakness created by Karl approaching from the west.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will pass over 27 to 28 deg C waters supportive for tropical development. A mass of dry air lies to the northwest of this tropical cyclone...due to upper convergence on the west side of the northeast Atlantic upper trough mentioned in the above atmospheric outlook section. As long as shear remains low...this tropical cyclone will be able to ward off this dry air by producing thunderstorms stacked with the circulation. However by 72 hours and beyond when the shear is forecast to increase...the shear may waft in this dry air which could exacerbate the weakening of this system.

**Forecast graphic not available tonight due to difficulties in personal internet access**

24 Hr Forecast (0000Z Sep 21)...50 mph maximum sustained wind tropical storm centered at 14.5N-34W

48 Hr Forecast (0000Z Sep 22)...70 mph maximum sustained wind tropical storm centered at 17.5N-37W

72 Hr Forecast (0000Z Sep 23)...60 mph maximum sustained wind tropical storm centered at 21.5N-39.5W

96 Hr Forecast (0000Z Sep 24)...40 mph maximum sustained wind tropical storm centered at 24.5N-42W

120 Hr Forecast (0000Z Sep 25)...40 mph maximum sustained wind tropical storm centered at 27.5N-44.5W

Track Forecast...I have updated my track forecast to be slightly south and east of the previous due to the initial 0000Z position (listed in the above current prognosis) being slightly south and east of the prior forecast track.

Intensity Forecast...I have slightly raised my intensity forecast as this system is already a tropical depression. The intensity forecast is similar to what I showed for this system in discussion #121 as that forecast predicted tropical depression status by tonight. The intensity forecast shows strengthening through 48 hours..followed by weakening by 72 to 96 hours when the shear increases per the above atmospheric outlook section. Weakening is stopped by 120 hours when this system reaches a lower shear environment also per the above atmospheric outlook.

Impact Forecast...Sea swells and rough seas within the storm and storm vicinity are expected to develop as this system acquires tropical storm strength.

2016 Atlantic Hurricane Season Birdseye Discussion #122

By: NCHurricane2009, 5:51 AM GMT on September 19, 2016

...MONDAY SEPTEMBER 19 2016 1:53 AM EDT...
The following statement concerns area of interest #1 marked offshore of the southeastern United States in the atmospheric features chart below. As the upper ridge west of Julia moved on top of Julia...it displaced all of its thunderstorm activity far to the southeast with Julia's swirl center failing to produce renewed thunderstorm activity under the lower shear and enhanced outflow of the upper ridge. Therefore Julia has been downgraded from a tropical depression to a remnant low tonight. This is my final statment on Julia on this blog unless it re-produces thunderstorm activity beneath the more favorable low shear/enhanced upper outflow environment. It should be noted this window of favorable conditions will be short-lived as the large upper trough over the eastern United States is expected to leave behind a shortwave upper trough that will near and unfavorably shear this system by 48 hours.

Tropical Storm Karl not strengthening at this time while dealing with unfavorable upper vorticity and dry air in its path. This upper vorticity is expected to gradually dissipate which may allow Karl to briskly strengthen and possibly become a hurricane while passing north of the Caribbean Islands and into the western Atlantic later this week. See first special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. Satellite imagery suggests the tropical wave in this region is slowly becoming better organized...and upper-level winds are expected to remain favorable in the eastern tropical Atlantic with the persistence of the upper anticyclone that aided in the formation of Tropical Storm Karl a few days ago. Therefore this tropical wave could strengthen into a tropical storm in this environment over the next few days. See second special feature section below for additional details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1933Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...Karl has not strengthened as expected...and in fact has become less organized it appears for a number of reasons. First bits of what's left of the nearby upper vortex that was shearing Karl (marked by blue-dashed lines over Karl in the above atmospheric features chart) have retrograded westward with the tropical storm and continue to disrupt the organization of the thunderstorm activity. Second the tropical storm has ran into dry air. An inspection of water vapor imagery over the last few days suggest this dry air originated west of the Canary Islands on September 11...created by upper-level convergence and sinking on the west side of upper troughing in the northeast Atlantic...and wafted southwestward into the path of Karl by upper convergence and northerly flow on the east side of the large upper anticyclone that has persisted in the central Atlantic. Also visible satellite over the past couple of days shows Karl's low-level circulation is somewhat large and broad...which may mean the tropical storm lacks a focused enough center to produce strong surface convergence to boost thunderstorm activity that would help it combat the dry air and what's left of the overhead upper vorticity (latent heat release from thunderstorms would help elminate the colder core upper vorticity). As of 0000Z...the center of Karl passed over 18.2N-46W.

Atmospheric Outlook for the Forecast Period...In the next few days...atmospheric conditions are still expected to become more conducive for additional development of Karl as the upper vorticity lingering over Karl and upper vortex currently near 57.5W longitude are expected to dissipate...which will allow the large favorble central Atlantic upper anticyclone to grow and stay collocated with Karl. The track of Karl is expected to have a more northward angle by 48 hours and beyond due to the 1009 mb frontal depression currently over eastern Canada...and another stronger frontal cyclone following behind currently over western Canada...both moving into the Atlantic. However the 1019 mb ridge currently over Arkansas will strengthen to the south of these frontal cyclones while moving into the west Atlantic...which will help prevent either cyclone from recurving Karl northeastward during the forecast period. Also the upper vortex currently in the eastern Caribbean will move westward while growing in size...with this feature also likely contributing to the northward lean in track from 48 to 120 hours.

Thermodynamic Outlook for the Forecast Period...On the current forecast track...Karl will move from not as favorable dry air and 28 to 29 deg C waters to more favorable less dry air and 30 to 31 deg C waters north of the Caribbean and south of Bermuda. Therefore the thermodynamic outlook becomes increasingly favorable for Karl as we progress through the 120-hour forecast period.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 20)...35 mph maximum sustained wind tropical depression centered at 18.5N-51W

48 Hr Forecast (0000Z Sep 21)...35 mph maximum sustained wind tropical depression centered at 20N-56W

72 Hr Forecast (0000Z Sep 22)...45 mph maximum sustained wind tropical depression centered at 21.5N-60W

96 Hr Forecast (0000Z Sep 23)...65 mph maximum sustained wind tropical storm centered at at 23N-65W

120 Hr Forecast (0000Z Sep 24)...85 mph maximum sustained wind hurricane centered at 25N-70W

Track Forecast...No changes to the track forecast as Karl is essentially on par with the previous forecast.

Intensity Forecast...I have significantly lowered the intensity forecast due to the currently poor state of Karl. I forecast Karl to weaken to a tropical depression in the next 48 hours till it clears the drier air and reaches the more moist air currently seen south of Bermuda and north the Caribbean. It may also take 48 hours or a little longer for the overhead upper vorticity and upper vortex currently near 57.5W longitude to dissipate as Karl's lack of thunderstorm activity/latent heat release may allow these cold core upper features to linger. I then show a brisk strengthening rate by 72 hours and beyond due to the latest upper wind forecast which still shows the large favorable upper anticyclone in the central Atlantic expanding and staying collocated with Karl which will help keep shear favorably low and upper outflow favorably high...and due to the very favorable 30 to 31 deg C waters Karl will be over by that time.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with removal of the swath where I forecast Karl to lose tropical storm strength..and then re-development and growth of the swath where I forecast Karl to strengthen.

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE INVEST 96-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...The vigorous tropical wave in the eastern tropical Atlantic has only slowly become better organized..but the organization appears to have quickened around 0000Z and 0300Z tonight with Meteosat-9 satellite showing the thunderstorm activity becoming concentrated and circular near the center of circulation. However I have slightly lowered the intensity forecast as the rate of organization has been a bit slower than I previously anticipated. As of 0000Z the center of circulation passed 13N-25W...which is slightly southeast of the previous track forecast and therefore my updated forecast is adjusted southeast accordingly.

Atmospheric Outlook for the Forecast Period...As Karl strengthens while moving toward the west Atlantic in the coming days...latent heat release of its thunderstorm activity is likely to pump up a warm core upper anticyclone currently in the central Atlantic...and in turn the latest computer model runs show the east-west upper trough currently southeast of Newfoundland in the north-central Atlantic diving southeastward around the east side of this anticyclone and toward this system. This upper trough is likely to bend the track northward and begin unfavorably shearing this system by the later part of the forecast period. Thus the later part of the forecast track shows a northward bend while the later part of the intensity forecast shows weakening.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will pass over 27 to 29 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 20)...Tropical low centered at 13.5N-29.5W

48 Hr Forecast (0000Z Sep 21)...40 mph maximum sustained wind tropical storm centered at 14N-34.5W

72 Hr Forecast (0000Z Sep 22)...60 mph maximum sustained wind tropical storm centered at 17N-37.5W

96 Hr Forecast (0000Z Sep 23)...60 mph maximum sustained wind tropical storm centered at 21N-40W

120 Hr Forecast (0000Z Sep 24)...50 mph maximum sustained wind tropical storm centered at 24N-42.5W

2016 Atlantic Hurricane Season Birdseye Discussion #121

By: NCHurricane2009, 6:36 AM GMT on September 18, 2016

...SUNDAY SEPTEMBER 18 2016 2:45 AM EDT...
Julia survives the current wind shear episode as a minimal tropical depression and now has a chance to re-develop offshore of the southeastern United States in the coming days as shear will reduce. See first special feature section for additional details on this situation. Visit www.nhc.noaa.gov for up to the minute lastest information on Julia.

Tropical Storm Karl not strengthening at this time while dealing with the first of two unfavorable upper vortices in its path. Both upper vortices are expected to gradually dissipate which may allow Karl to significantly strengthen into a strong hurricane while passing north of the eastern Caribbean Islands and into the western Atlantic by early next week. See second special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic in the atmospheric features chart below. Although satellite imagery suggests the tropical wave in this region has not become any better organized...upper-level winds are expected to remain favorable in the eastern tropical Atlantic with the persistence of the upper anticyclone that recently aided in the formation of Tropical Storm Karl...therefore this tropical wave could strengthen into a tropical storm in this environment over the next few days. See third special feature section below for additional details. Regardless of development or not...squally weather with heavy rain and gusty winds on the north side of the tropcal wave could pass over the islands of the Republic of Cabo Verde over the next day.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1931Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL DEPRESSION JULIA...
Current Prognosis...Julia essentially has been stationary offshore of the southeastern United States and under vertical shear was hanging on to minimal tropical depression status for the last 24 hours while firing pockets of thunderstorms east of the center...and ocassionally firing a burst of storms near the center. Julia's survival under shear may have to do with the rather warm 29 to 30 deg C waters its parked over that have allowed it to fire thunderstorm activity...and with shear forecast to relax Julia could linger as a tropical cyclone for a few more days. As of 0000Z the surface center of Julia was located at 30.6N-76.5W.

Atmospheric Outlook for the Forecast Period...Julia's lack of motion over the last day may have had to do with the fact its not been able to escape the influence of the amplifying upper trough in the northwest Atlantic to its northeast. In fact the base of this trough has cut-off into an upper vortex immediately northeast of Julia due to the warm air advection ahead of the north-central US 1006 mb frontal cyclone and resultant amplification of an upper ridge immediately west of Julia. The nearby cut-off upper vortex maybe trying to pull Julia east while the 1033 mb ridge in the northwest Atlantic maybe trying to push Julia west...and Julia has gone nowhere. Some northward motion may begin shortly as the upper vortex de-amplifies and moves away while low-level steering currents become southerly ahead of the 1006 mb frontal cyclone. However this northward motion will be slow and probably come to a stop in 48 to 72 hours as the 1018 mb ridge currently over Missouri nears Julia and pins it against the 1033 mb northwest Atlantic ridge moving into the Atlantic. Strengthening is also possible during this time as the upper ridge immediately west of Julia overspreads it...which will reduce shear and enhance its upper outflow. Then as the 1018 mb ridge passes north of Julia while strengthening...it could steer Julia west-southwestward into the southeastern United States coast. Weakening is likely at 96 hours as a shortwave upper trough to be left behind by the north-central US 1006 mb frontal cyclone nears and shears Julia...but the weakening could be slowed at 120 hours as this shortwave upper trough weakens.

Thermodynamic Outlook for the Forecast Period...On the updated forecast track shown below...Julia will be over 28 to 29 deg C waters which will help it linger as a tropical cyclone over the next few days.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 19)...35 mph maximum sustained wind tropical depression centered at 31.8N-77W

48 Hr Forecat (0000Z Sep 20)...45 mph maximum sustained wind tropical storm centered at 32.5N-77W

72 Hr Forecast (0000Z Sep 21)...50 mph maximum sustained wind tropical storm centered at 32.5N-77W

96 Hr Forecast (0000Z Sep 22)...35 mph maximum sustained wind tropical depression centered at 32.2N-78.2W

120 Hr Forecast (0000Z Sep 23)...30 mph maximum sustained wind tropical depression approaching landfall at the southern tip of South Carolina at 32.1N-81.2W

Track Forecast...I was previously expecting Julia to dissipate under shear...but clearly this is not happening. Now as shear is expected to reduce...I have had to create a track forecast for the next few days while predicting Julia to last a few days more. My track forecast shows a northward motion...stall...and then a west-southwest motion for the next five days per the detials in the above atmospheric outlook section.

Intensity Forecast...My updated intensity forecast shows Julia re-strengthening as shear reduces in the next couple of days...followed by another round of weakening at the end of the forecast period during another round of wind shear.

Impact Forecast...Some tropical storm force winds are possible well offshore of the southeastern United States should Julia regain tropical storm status.

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...Karl remains a sheared tropical storm while it passes beneath the shearing westerlies on the southwest side of an upper vortex. The shear is keeping the thunderstorm activity northeast of Karl's swirl center...although very recently some thunderstorm activity is beginning to cover the center as it begins to escape the upper vortex. As of 0000Z the center of Karl was located at 17.9N-40.9W. When compared to the 0000Z center fix from yesterday...Karl has slid a little south in its westward track. This is likely to have been caused by northerly flow on the west side of the upper vortex and/or the strengthening of the 1033 mb ridge northwest Atlantic ridge as this ridge spreads further into the Atlantic.

Atmospheric Outlook for the Forecast Period...In the next 24 hours Karl will move away from the upper vortex currently shearing it and take advantage of more favorable conditions on the south side of the large upper anticyclone currently in the central Atlantic. The latest model runs suggest the other upper vortex currently at 55W longitude will dissipate fast enough to avoid disrupting the development of Karl. The track of Karl is expected to have a more northward angle by 72 hours and beyond due to the 1006 mb frontal cyclone currently over the north-central US...and another stronger frontal cyclone following behind from Canada...both moving into the Atlantic. However the 1018 mb ridge currently over Missouri will strengthen to the south of these frontal cyclones while moving into the west Atlantic...which will help prevent either cyclone from recurving Karl northeastward during the forecast period. Also the upper vortex currently in the eastern Caribbean will move westward while growing in size...with this feature also likely to contribute to the northward lean in track from 72 to 120 hours.

Thermodynamic Outlook for the Forecast Period...Karl will pass over 27 to 29 deg C waters for most of the forecast period...reaching warmer 30 to 31 deg C waters by the end of the 120-hour forecast period. Therefore water temps will be rather supportive for additional development of Karl in the coming days.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 19)...50 mph maximum sustained wind tropical storm centered at 18N-46W

48 Hr Forecast (0000Z Sep 20)...65 mph maximum sustained wind tropical storm centered at 18.5N-51W

72 Hr Forecast (0000Z Sep 21)...85 mph maximum sustained wind hurricane centered at 20N-56W

96 Hr Forecast (0000Z Sep 22)...105 mph maximum sustained wind hurricane centered at 21.5N-60W

120 Hr Forecast (0000Z Sep 23)...125 mph maximum sustained wind hurricane centered at 23N-65W

Track Forecast...My first few forecast points are adjusted slightly south and east due to the current initial position of Karl. However the later points have no eastward adjustment to keep up with the latest computer model guidance which shows Karl moving faster to the west by the end of the forecast period.

Intensity Forecast...I have slightly lowered the intensity forecast of Karl due to the initial strength of the storm which is slightly below the previous intensity forecast. With that said...I forecast Karl to strengthen into a major hurricane (115+ mph...or category 3+ hurricane) by 120 hours while the favorable central Atlantic upper anticyclone expands and stays collocated with Karl...and due to the warm 30 to 31 deg C sea-surface temps Karl will be traversing over by that time.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track. I grow the size of the swath by the end of the 120-hour forecast period in anticipation of strengthening.

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE INVEST 96-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...Over the last 24 hours the vigorous tropical wave that recently entered the eastern tropical Atlantic from Africa had an increase in thunderstorms and was becoming better organized during the daylight...only to lose some thunderstorm activity and become less organized with southwest-northeast elongation in satellite pictures this evening. Currently the bands of thunderstorm suggest the center of the elongated circulation is at approximately 13N-22W...which is slightly east of the previous forecast and therefore the updated forecast is adjusted eastward accordingly. The intensity forecast listed below is also lowered when compared to the previous due to the lack of progress in organization.

Atmospheric Outlook for the Forecast Period...As Karl strengthens while moving toward the west Atlantic in the coming days...latent heat release of its thunderstorm activity is likely to pump up a warm core upper anticyclone currently in the central Atlantic...and in turn the latest computer model runs show upper trough currently in the northwest Atlantic diving southeastward around the east side of this anticyclone and toward this system. This upper trough is likely to bend the track northward and begin unfavorably shearing this system by the end of the 120-hour forecast period. Thus the later part of the forecast track is adjusted northward and the intensity forecast shows a bit of weakening during this timeframe accordingly.

Thermodynamic Outlook for the Forecast Period...On the latest forecast track listed below...this system will pass over 27 to 29 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 19)...Tropical low centered just southwest of the Republic of Cabo Verde at 14N-26.5W

48 Hr Forecast (0000Z Sep 20)...35 mph maximum sustained wind tropical depression centered at 14.5N-31W

72 Hr Forecast (0000Z Sep 21)...50 mph maximum sustained wind tropical storm centered at 15N-36W

96 Hr Forecast (0000Z Sep 22)...70 mph maximum sustained wind tropical storm centered at 18N-39W

120 Hr Forecast (0000Z Sep 23)...65 mph maximum sustained wind tropical storm centered at 22N-41.5W

2016 Atlantic Hurricane Season Birdseye Discussion #120

By: NCHurricane2009, 6:36 AM GMT on September 17, 2016

...SATURDAY SEPTEMBER 17 2016 2:40 AM EDT...
Julia continues drifting erratically offshore of the southeastern United States under shifting steering currents while weakening to a tropical depression under hostile westerly vertical shear. See first special feature section for additional details on Julia. Visit www.nhc.noaa.gov for up to the minute lastest information on Julia.

The following statement concerns area of interest #1 marked in the north-central Atlantic in the atmospheric features chart below. Ian transitions from a tropical storm to a non-tropical remnant gale as expected...therefore this is my final statement on Ian on this blog.

Tropical Storm Karl not strengthening at this time while dealing with the first of two unfavorable upper vortices in its path. Both upper vortices are expected to gradually dissipate which may allow Karl to significantly strengthen into a strong hurricane while passing north of the eastern Caribbean Islands and into the western Atlantic by early next week. See second special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

In addition to Ian...Julia...and Karl...see the following statements for two other areas of interest.

The following statement concerns area of interest #2 marked over the northwestern Gulf of Mexico in the atmospheric features chart below. The weak surface low in this area has remained organized...but has run out of time to become a tropical cyclone while making landfall in eastern Texas and Louisiana. Currently the rainfall with this system is weak on doppler radar as this system has once again lost thunderstorm activity during the nighttime hours...but as this system becomes drawn northward and becomes absorbed by the cold front moving across the central United States...the tropical moisture it has pumped in may enhance rainfall along the front resulting in isolated flash flooding along the front. This is my final statement on this system on this blog.

The following statement concerns area of interest #3 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Although satellite imagery suggests the tropical wave emerging from Africa has become less organized...upper-level winds are expected to remain favorable in the eastern tropical Atlantic with the persistence of the upper anticyclone that recently aided in the formation of Tropical Storm Karl...therefore this tropical wave could strengthen into a tropical storm or hurricane in this environment over the next few days. See third special feature section below for additional details. Regardless of development or not...squally weather with heavy rain and gusty winds on the north side of the tropcal wave could pass over the islands of the Republic of Cabo Verde over the next couple of days.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 0131Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL DEPRESSION JULIA...
Current Prognosis...Julia continues to drift southeastward offshore of the southeatern United States and was hanging on to minimal tropical storm status for most of the last 24 hours while firing renewed thunderstorm activity near the center. However tonight as the thunderstorm activity weakens while getting sheared away...Julia has finally weakened to a tropical depression. As of 0000Z the surface center of Julia was located at 30.2N-76.2W.

Atmospheric Outlook for the Forecast Period...Westerly shear per the above current prognosis should cause Julia to continue weakening going forward. The 1028 mb ridge currently moving into the northwestern Atlantic should cause Julia...or whatever is left of it...to loop back westward toward the southeastern United States coast. Southerly low-level flow and resultant warm air advection ahead of the 1007 mb frontal cyclone over the north-central United States and southern Canada should amplify an upper ridge to the west of Julia...with northerly upper flow and upper convergence on the east side of the upper ridge shearing and suppressing Julia. Therefore whatever is left of Julia should be weak and benign should the remnants loop back toward the southeastern United States.

Thermodynamic Outlook for the Forecast Period...Although Julia should be parked over rather warm 29 to 30 deg C waters offshore of the southeastern United States...unfavorable atmospheric conditions are expected to suppress Julia from this point forward per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 18)...Remnant low centered at 30N-77.5W

Track Forecast...Julia has drifted southeastward instead of southwestward over the last 24 hours...with the eastward component being caused by the upper trough amplifying over the northwest Atlantic to the northeast of Julia. Perhaps the tail end of the surface cold front associated with the upper trough may have also played a role in the eastward lean in the track. However the latest satellite frames during sunset and this evening suggest the track is finally leaning westward as the 1028 mb ridge moving into the northwest Atlantic is finally getting a grip on steering Julia. Therefore I show a southwestward track in the next 24 hours.

Intensity Forecast...With the thunderstorms becoming seperated from the surface per the above current prognosis...my above intensity forecast assumes Julia will dissipate as a tropical cyclone in the next 24 hours due to persistence in westerly shear.

Impact Forecast...No signficant impacts are expected as Julia is now a weak tropical depression forecast to become a remnant low.

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...Karl remains a sheared tropical storm while it passes beneath the shearing westerlies on the south side of an upper vortex. The shear is keeping the thunderstorm activity northeast of Karl's swirl center. As of 0000Z the center of Karl was located at 18.5N-36.5W.

Atmospheric Outlook for the Forecast Period...It is apparent that Karl is not weakening but instead maintaining strength while getting sheared by the upper vortex mentioned in the above current prognosis section. The 1800Z GFS model run suggests the upper vortex might retrograde a bit westward with Karl while it moves around the southeast side of the large upper anticyclone in the central Atlantic...and therefore the next 24 hours Karl is not likely to stregnthen while still sheared by the upper vortex. However after 24 hours Karl will move away from this upper vortex and take advantage of more favorable conditions on the south side of the aforementioned central Atlantic upper anticyclone. The latest model runs suggest the other upper vortex currently at 55W longitude will dissipate fast enough to avoid disrupting the development of Karl. The track of Karl is expected to bend more northward by 96 and 120 hours due to the 1007 mb frontal cyclone currently over the north-central US...and another stronger frontal cyclone following behind from Canada...both moving into the Atlantic. Also another cut-off upper vortex has developed over the Lesser Antilles at 60W longitude while fracturing from the base of the upper trough currently in the north-central Atlantic associated with Ian's non-tropical remnants. This upper vortex will move westward into the Caribbean and grow in size...and is also likely to help with the northward lean in Karl's track at the end of the 120-hour forecast period.

Thermodynamic Outlook for the Forecast Period...This tropical cyclone will pass over 27 to 29 deg C waters for most of the forecast period...reaching warmer 30 deg C waters by the end of the 120-hour forecast period. Therefore water temps will be rather supportive for additional development of Karl in the coming days.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 18)...45 mph maximum sustained wind tropical storm centered at 18.5N-41.5W

48 Hr Forecast (0000Z Sep 19)...60 mph maximum sustained wind tropical storm centered at 18.5N-46.5W

72 Hr Forecast (0000Z Sep 20)...75 mph maximum sustained wind hurricane centered at 19N-51.5W

96 Hr Forecast (0000Z Sep 21)...90 mph maximum sustained wind hurricane centered at 20.5N-56W

120 Hr Forecast (0000Z Sep 22)...110 mph maximum sustained wind hurricane centered at 22.5N-60W

Track Forecast...Karl is slightly east of my previous forecast track and therefore the updated forecast track is adjusted accordingly. Also the northward angle of the track forecast for the first 48 hours has been removed as Karl is now seen tracking straight west along 18.5N latitude and some model runs have suggested Karl may even lean a bit southward in track. The southward lean may be induced by the southwest side of the upper vortex that Karl is currently dealing with...or by the strengthening of the 1028 mb northwest Atlantic ridge as this ridge spreads into the Atlantic (Ian's non-tropical remnant gale is pulling cool air southward on its west side...which in turn is amplifying the upper trough in the north-central Atlantic...and in turn strengthening upper convergence on the west side of the upper trough will strengthen this surface ridge).

Intensity Forecast...I have significantly raised my intensity forecast on Karl for a number of reasons. First...Karl has not weakened while interacting with the first upper vortex its dealing with. Second...the eastward adjustment in the forecast track means more distance between Karl and the diminishing upper vortex currently at 55W longitude...which is reducing the probability that Karl will deal with shear from that upper vortex during the middle of the forecast period.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track. I grow the size of the swath by the end of the 120-hour forecast period in anticipation of strengthening.

...SPECIAL FEATURE...STRONG TROPICAL WAVE EMERGING FROM WESTERN AFRICA...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...The vigorous tropical wave over western Africa has become less organized as it emerges into the eastern tropical Atlantic. Currently there are scattered bands of thunderstorms outlining a center of rotation offshore of Africa at 12N-18W. The intensity forecast listed below is lowered when compared to the previous due to the less organized satellite appearance.

Atmospheric Outlook for the Forecast Period...Warm air advection ahead Ian's non-tropical remnant gale has amplified upper ridging in the northeast Atlantic...which in turn has pushed the upper trough currently in the northeast Atlantic southward toward this system. However it now appears it may take this system a little longer to become a strong-tall enough tropical cyclone to feel steering influence from this upper trough...and the 1800Z GFS shows this upper trough shifting eastward and away more than before...thus the updated track forecast listed below is a southward shift when compared to the previous. As the upper vortex shearing Tropical Storm Karl to the west dissipates and as the upper vortex currently at 55W longitude also dissipates...there will be a region of widespread favorable upper anticyclonic flow with low shear and good upper outflow potentially aiding in significant development of this system as it moves westward across the Atlantic tropics in the coming days.

Thermodynamic Outlook for the Forecast Period...On the forecast track listed below...this system will pass over 28 to 29 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 18)...Tropical low centered just south-southeast of the Republic of Cabo Verde at 13N-23.5W

48 Hr Forecast (0000Z Sep 19)...35 mph maximum sustained wind tropical depressioncentered just southwest of the Republic of Cabo Verde at 14N-28W

72 Hr Forecast (0000Z Sep 20)...50 mph maximum sustained wind tropical storm centered at 14.5N-32.5W

96 Hr Forecast (0000Z Sep 21)...75 mph maximum sustained wind hurricane centered at 15N-37.5W

120 Hr Forecast (0000Z Sep 22)...95 mph maximum sustained wind hurricane centered at 15.5N-42.5W

2016 Atlantic Hurricane Season Birdseye Discussion #119

By: NCHurricane2009, 6:35 AM GMT on September 16, 2016

...FRIDAY SEPTEMBER 16 2016 2:45 AM EDT...
Tropical Storm Julia is looping eratically offshore of the southeastern United States under shifting steering currents and is expected to weaken into a remnant low under hostile westerly vertical shear. See first special feature section for additional details on Julia. Visit www.nhc.noaa.gov for up to the minute lastest information on Julia.

Tropical Storm Ian continues to curve northeastward into the open north-central Atlantic where it will transition into a strong non-tropical remnant gale in the next 24 hours. See second special feature section below for additional details on Ian. Visit www.nhc.noaa.gov for up to the minute latest information on Ian.

Tropical depression twelve strengthens into Tropical Storm Karl while pulling away from the Republic of Cabo Verde. Over the next few days additional development of Karl is expected to be slow while it deals with a pair of unfavorable upper vortices that lie ahead in its path. See third special feature section below for more details on Karl. Visit www.nhc.noaa.gov for up to the minute latest information on Karl.

In addition to our three active tropical cyclones...see the following statements for two other areas of interest.

The following statement concerns area of interest #1 marked over the Gulf of Mexico in the atmospheric features chart below. The weak surface low in the Gulf of Mexico has become better organized but has not produced thunderstorms for a sustained period to strengthen into a tropical cyclone. While being steered northwestward by the 1028 mb ridge over the northeast United States...time is running out for this system to become a tropical cyclone as it is sliding away from the favorable upper anticyclone that recently developed over the Gulf...and is moving into more hostile westerly shear north of the anticyclone and toward landfall in eastern Texas and Louisiana. Regardless of tropical cyclone formation or not...this system may produce heavy rainfall with isolated flash flooding if it re-develops a burst of thunderstorms at landfall.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. Satellite imagery suggests the tropical wave that was over southern Mali last night has become the dominant wave in this region while rapidly strengthening and organizing further. Upper-level winds are expected to remain favorable in the eastern tropical Atlantic with the persistence of the upper anticyclone that recently aided in the formation of Tropical Storm Karl...therefore this tropical wave could strengthen into a tropical storm or hurricane in the eastern tropical Atlantic in this environment over the next few days. See fourth special feature section below for additional details on this developing situation. Interests in the Republic of Cabo Verde should watch the progress of this tropical wave as the center of circulation is expected to pass nearby in the next 48 hours.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM JULIA...
Current Prognosis...Julia's eastward track has turned southward tonight...and likely loop back more westward while steered by the 1028 mb ridge over the northeastern United States. As of 0000Z the surface center of Julia was located offshore of the southeastern United States at 31.6N-77.4W. Strong upper-level westerlies continue to shear away the thunderstorm activity from Julia's center...at one point causing Julia to weaken to a tropical depression in the last 24 hours...only to become a tropical storm again late this afternoon and tonight. However the latest satellite imagery shows the thunderstorm activity displaced further away from the surface center more than ever and Julia is likely to weaken to a tropical depression again.

Atmospheric Outlook for the Forecast Period...Westerly shear per the above current prognosis should cause Julia to weaken going forward. The 1028 mb ridge currently over the northeastern United States should cause Julia...or whatever is left of it...to loop back westward toward the southeastern United States coast. Southerly low-level flow and resultant warm air advection ahead of a frontal cyclone developing west of the surface ridge should amplify an upper ridge to the west of Julia...with northerly upper flow and upper convergence on the east side of the upper ridge shearing and suppressing Julia. Therefore whatever is left of Julia should be weak and benign should the remnants loop back toward the southeastern United States.

Thermodynamic Outlook for the Forecast Period...Although Julia should be parked over rather warm 29 to 30 deg C waters offshore of the southeastern United States...unfavorable atmospheric conditions are expected to suppress Julia from this point forward per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 17)...35 mph maximum sustained wind tropical depression dissipating into remnant low...centered at 30.5N-78.5W

Track Forecast...I show a southwestward change in position in the next 24 hours as I forecast the 1028 mb surface ridge currently over the northeastern United States to bend the current southward track in a more westward dirction.

Intensity Forecast...With the thunderstorms becoming seperated from the surface per the above current prognosis...my above intensity forecast assumes Julia will dissipate as a tropical cyclone in the next 24 hours due to persistence in westerly shear.

Impact Forecast...Impact swath is drawn to the size of the 11 PM EDT NHC tropical storm wind radius...with the assumption Julia will lose tropical storm strength fairly soon near its current location.

...SPECIAL FEATURE...TROPICAL STORM IAN...
Current Prognosis...The upper vortex that was over Ian has become absorbed by an upper trough incoming from the northwest...which has allowed Ian to fire thunderstorm activity closer to the center and in a more solid fashion with the suppressing upper-convergence of the upper vortex gone. However the thunderstorm activity is biased to the north side of the circulation due to strong southwesterly vertical shear ahead of the upper trough...and Ian's cloudiness is also beginning to assimilate into the larger-scale cloudieness associated with the 998 mb surface frontal cyclone emerging from eastern Canada that is supported by the upper trough. The shear and also perhaps increasingly cooler waters has prevented Ian from additional strengthening. As of 0000Z the center of Ian passed over 40.1N-47W.

Atmospheric Outlook for the Forecast Period...Ian is accelerating in southwesterly flow ahead of the 998 mb frontal cyclone and upper trough mentioned in the above current prognosis section. In the next 24 hours...Ian is likely to strengthen...but because it will be transitioning into a non-tropical remnant gale supported by divergence on the east side of the upper trough.

Thermodynamic Outlook for the Forecast Period...This system has crossed the 26 deg C isotherm and will be entering even cooler waters over the next 24 hours...aiding in the transition to non-tropical per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 17)...Non-tropical remnant gale centered at 53.5N-35W

Track Forecast...Ian is 1.5E longitude off of my previous forecast track per the above current prognosis 0000Z fix...and thus the updated track forecast is adjusted eastward by 1.5E accordingly.

Intensity Forecast...Ian should strengthen in the next 24 hours and beyond as it transitions to non-tropical per the above atmopsheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track.

...SPECIAL FEATURE...TROPICAL STORM KARL...
Current Prognosis...Tropical depression twelve has strengthened to Tropical Storm Karl tonight while firing strong thunderstorm bursts over and east of the center. The thunderstorm activity is biased to the east of the center due to westerly vertical shear from an upper vortex immediately west of the tropical storm...which has formed in relatively lower pressures between the warm core upper anticyclone trying to form overhead and warm core upper anticyclone in the central Atlantic which was previously pumped up by Tropical Storm Ian's thunderstorm latent heat release. As of 0000Z the center of Karl was located at 18N-32W.

Atmospheric Outlook for the Forecast Period...As expected...shear is increasing as a new upper vortex has formed between the overhead anticyclone and central Atlantic upper anticyclone that was pumped up by Ian's thunderstorm latent heat release earlier. I forecast dissipation of this system as a tropical cyclone by 48 hours when the forecast track takes it beneath this new upper vortex. Latest model runs suggest the other cut-off upper vortex currently at 47W longitude will dissipate fast enough to allow this system to take advantage of more favorable conditions on the south side of the aforementioned central Atlantic upper anticyclone...and so I forecast this system to re-generate as a tropical cyclone in 72 hours...although this system may encounter some light southerly vertical shear from the dissipating upper vortex in 96 hours which could slow the re-development during this timeframe. More rapid strengthening is shown at 120 hours as upper anticyclonic flow expands over this system after the upper vortex dissipates. A northward lean in track is possible at 120 hours as the frontal cyclone currently developing over the north-central US moves into the Atlantic...and may also be induced by a large upper vortex forecast to develop across the Caribbean Sea. This upper vortex is expected for form as the base of the upper trough currently in the northwest Atlantic cuts off and retrogrades southwestward.

Thermodynamic Outlook for the Forecast Period...This tropical cyclone will pass over 27 to 29 deg C waters that will be supportive of tropical development.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 17)...Sheared 35 mph maximum sustained wind tropical depression centered at 18.5N-37.5W

48 Hr Forecast (0000Z Sep 18)...Remnant low centered at 19N-42.5W

72 Hr Forecast (0000Z Sep 19)...35 mph maximum sustained wind tropical depression centered at 19.5N-47.5W

96 Hr Forecast (0000Z Sep 20)...45 mph maximum sustained wind tropical storm under light southerly vertical shear centered at 20N-52.5W

120 Hr Forecast (0000Z Sep 21)...60 mph maximum sustained wind troipcal storm centered at 21.5N-57W

Track Forecast...Unlike prior forecasts...Karl is now south of the previous forecast track...thus I have adjusted the forecast points southward and have reduced the northward angle of the forecast track to be more in alignment with Karl's recent more westward track.

Intensity Forecast...Karl has been following my previous two intensity forecasts perfectly...and so once again I have made no changes. I still forecast Karl to dissipate as a tropical cyclone by 0000Z September 18...followed by a forecast re-development from 0000Z September 19 and onwards per the above atmospheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track. I grow the size of the swath by the end of the 120-hour forecast period in anticipation of some strengthening.

...SPECIAL FEATURE...STRONG TROPICAL WAVE EMERGING FROM WESTERN AFRICA...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...A tropical wave that was over southern Mali 24 hours ago has continued strengthen and become better organized on satellite pictures while continuing westward. As of 0000Z satellite imagery suggests the tropical wave has spun up into a well-organized tropical low about to emerge into the eastern tropical Atlantic...centered at 11N-13W.

Atmospheric Outlook for the Forecast Period...As Tropical Storm Ian transitions into a non-tropical remnant gale in the north-central Atlantic...warm air advection ahead of the gale will amplify upper ridging in the northeast Atlantic...which in turn will push the upper trough currently in the norhteast Atlantic southward toward this system. Due to the well-organized initial structure...my forecast below assumes this system will quickly develop into a tropical storm strong and tall enough to have its track bent northward by this upper trough. During the latter half of the 120 hour forecast period...computer models show this upper trough de-amplify which will keep the shear over this system favorably low and allow the track of this system to bend back more westward.

Thermodynamic Outlook for the Forecast Period...On the forecast track listed below...this system will pass over 28 to 29 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 17)...Tropical low centered at 12N-19W

48 Hr Forecast (0000Z Sep 18)...45 mph maximum sustained wind tropical storm passing just south of the Republic of Cabo Verde...centered at 13N-24.5W

72 Hr Forecast (0000Z Sep 19)...60 mph maximum sustained wind tropical storm centered just southwest of the Republic of Cabo Verde at 15N-28.5W

96 Hr Forecast (0000Z Sep 20)...75 mph maximum sustained wind hurricane centered at 16.5N-33W

120 Hr Forecast (0000Z Sep 21)...90 mph maximum sustained wind hurricane centered at 17.5N-38W

2016 Atlantic Hurricane Season Birdseye Discussion #118

By: NCHurricane2009, 7:19 AM GMT on September 15, 2016

...THURSDAY SEPTEMBER 15 2016 3:30 AM EDT...
Conditions are improving along the southeastern United States coast as Tropical Storm Julia begins to become less organized under increasing westerly vertical shear. See first special feature section for additional details on Julia. Visit www.nhc.noaa.gov for up to the minute lastest information on Julia.

Tropical Storm Ian continues to curve northward toward the open north-central Atlantic where it will transition into a strong non-tropical remnant gale. See second special feature section below for additional details on Ian. Visit www.nhc.noaa.gov for up to the minute latest information on Ian.

The organized tropical wave that was passing over the Republic of Cabo Verde has strengthened into tropical depression twelve...and conditions on the islands will improve as the tropical depression moves away later today. See third special feature section below for additional details on the newly-formed tropical depression. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression twelve.

In addition to our three active tropical cyclones...see the following statements for two other areas of interest.

The following statement concerns area of interest #1 marked over the Gulf of Mexico in the atmospheric features chart below. The weak surface low that was moving away from the Florida Keys in discussion #114 on Sunday has made a comeback...as the upper trough southern fracture that was shearing it is now breaking up while a more favorable upper anticyclone forms in its wake. This anticyclone has reduced the shear and enhanced the upper outflow such that this surface low has re-developed thunderstorm activity over the center. I have not upgraded this surface low back to a special feature with a tropical cyclone formation forecast due to the thunderstorm activity dissipating tonight. However conditions will remain favorable for development as it moves northwestward toward Texas or Louisiana in the next day or so while steered by the southwest side of the 1027 mb ridge currently over the Great Lakes. Interests in coastal Texas and Lousiana should keep an eye on this disturbed weather as a short-lived tropical cyclone cannot be ruled out.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. Satellite imagery suggests the tropical wave that was approaching the west coast of Africa and eastern tropical Atlantic last night has signficantly weakened. However another vigorous and well-organized tropical wave is moving into southern Mali over western Africa. Upper-level winds are expected to remain favorable in the eastern tropical Atlantic with the persistence of the upper anticyclone that is currently helping tropical depression twelve...and computer models continue to suggest that one of the two aforementioned tropical waves will develop in this environment. Therefore will continue to watch this area over the next few days.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0129Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM JULIA...
Current Prognosis...Julia has clearly tracked more eastward and moved offshore of the southeastern United States coast than previously forecast...perhaps while the surface center re-generated toward the heavier offshore thunderstorm activity and also while getting dragged by the cold front moving across the eastern United States from eastern Canada. As of 0000Z the surface center of Julia was located just offshore of southern South Carolina at 32N-80.1W and is slowing to a stall while becoming pinned down by the strong 1027 mb ridge moving into the Great Lakes region to the north of the tropical storm. Meanwhile strong upper-level westerlies at the base of the upper trough associated with the aforementioned cold front are beginning to shear away the thunderstorm activity from Julia's center.

Atmospheric Outlook for the Forecast Period...Increasing westerly shear per the above current prognosis should cause Julia to weaken going forward. Julia should soon stall while becoming pinned down by the strong 1027 mb ridge currently over the Great Lakes...with this surface ridge perhaps causing whatever is left of Julia to loop back westward toward the southeastern United States coast. Southerly low-level flow and resultant warm air advection ahead of a frontal cyclone developing west of the surface ridge should amplify an upper ridge to the west of Julia...with northerly upper flow and upper convergence on the east side of the upper ridge shearing and suppressing Julia. Therefore whatever is left of Julia should be weak and benign should the remnants loop back into the southeastern United States.

Thermodynamic Outlook for the Forecast Period...Although Julia should be parked over rather warm 29 to 30 deg C waters offshore of the southeastern United States...unfavorable atmospheric conditions are expected to suppress Julia from this point forward per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 16)...35 mph maximum sustained wind tropical depression dissipating into remnant low...centered offshore of southern South Carolina at 32N-79W

Track Forecast...Julia should drift eastward a little more or stall per the above current prognosis and atmospheric outlook sections.

Intensity Forecast...With the thunderstorms becoming seperated from the surface per the above current prognosis...my above intensity forecast assumes Julia will dissipate as a tropical cyclone in the next 24 hours due to increasing levels of westerly shear.

Impact Forecast...Impact swath is drawn to the size of the 11 PM EDT NHC tropical storm wind radius...with the assumption Julia will lose tropical storm strength fairly soon while stalling near its current location. Latest doppler radar shows the rain shield of Julia is clearing away from the southeast US coast due to westerly vertical shear pulling away thunderstorm activity from Julia...and therefore it appears the threat of heavy rain is over.

...SPECIAL FEATURE...TROPICAL STORM IAN...
Current Prognosis...Ian's structure has changed as its surface center and nearby upper vortex have whirled toward each other and have become vertically stacked. This suggests Ian may actually be more of a subtropical storm rather than a fully tropical one at the moment. Like a subtropical storm...the thunderstorm activity is being supported by instability induced by the cold temperatures of the upper vortex coupled with the warm waters at the surface. The thunderstorm activity around Ian is actually better organized and more symmetrically distributed around the center...better than any prior time in its life as Ian is a spot of low shear directly below the upper vortex center. However the thunderstorm intensity is generally weaker than before as the instability is not enough to support the prior stronger activity...and the upper vortex is producing oppressive upper convergence over Ian...thus Ian has not strengthened. As of 0000Z the center of Ian passed over 33.5N-53.5W.

Atmospheric Outlook for the Forecast Period...Ian is beginning to accelerate north-norhteastward while becoming steered by the surface cold front and its upper trough currently moving into the Atlantic from the northeastern US/eastern Canada. By 48 hours...Ian is likely to strengthen...but because it will be transitioning into a non-tropical remnant gale supported by divergence on the east side of the upper trough.

Thermodynamic Outlook for the Forecast Period...On the current forecast track...this system will be over 27 to 28 deg C waters supportive of tropical status for the first part of the forecast period...reaching waters well below 26 deg C by 48 hours which will help this system transition to non-tropical per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 16)...50 mph maximum sustained wind tropical storm centered at 40.5N-48.5W

48 Hr Forecast (0000Z Sep 17)...Non-tropical remnant gale centered at 53.5N-36.5W

Track Forecast...Ian is 1.5N latitude and 1.5E longitude off of my previous forecast track per the above current prognosis 0000Z fix...and thus the updated track forecast is adjusted northeastward by 1.5N and 1.5E accordingly.

Intensity Forecast...As the above current prognosis notes...Ian is being suppressed by the overhead upper vortex...and in the next 24 hours Ian will move into a hostile southwesterly shear environment ahaed of the incoming upper trough approaching from the northeastern US/eastern Cananda. Therefore I forecast no additional strengthening of Ian as a tropical cyclone. However Ian could strengthen further by 48 hours and beyond as it transitions to non-tropical per the above atmopsheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track.

...SPECIAL FEATURE...TROPICAL DEPRESSION TWELVE...
Current Prognosis...While passing over the northwestern Republic of Cabo Verde islands this past afternoon...the strong tropical wave in the eastern Atlantic strengthened into the twelvth tropical depression of the 2016 Atlantic Hurricane Season. Most recently...nighttime infrared shows a circular thunderstorm burst surrounded by curved thunderstorm bands. However a faint orb of low-level clouds is poking out to the west of the burst and bands and closer to the 0000Z center fix of 17.6N-32.5W suggested by the National Hurricane Center 11 PM EDT advisory...suggesting that the low-level center may already be beginning to seperate from the thunderstorm activity due to westerly vertical shear. This shear is developing due to the development of an upper trough immediately west of the tropical depression...forming in relatively lower pressures between the warm core upper anticyclone trying to form over the depression and warm core upper anticyclone in the central Atlantic which was pumped up by Tropical Storm Ian's thunderstorm latent heat release over the last couple of days. The 0000Z center fix is north of the previous forecast again...perhaps as the tropical depression was vertically tall enough to be tugged northward by the upper trough. However satellite animation from 0000Z to 0300Z...and also the NHC recorded storm track...shows the track is bending back more westward. As the tropical depression moves away from the Republic of Cabo Verde...weather conditions will improve later this morning.

Atmospheric Outlook for the Forecast Period...Tropical depression twelve has developed to the east of a cut-off upper vortex that has retrograded southwestward to 45W longitude...due to an upper anticyclone to the east of the upper vortex and over the tropical depression which helped its upper outflow and kept shear low. However over the next 72 hours...shear will be increasing as an upper trough and then new upper vortex develops between the overhead anticyclone and central Atlantic upper anticyclone that was pumped up by Ian's thunderstorm latent heat release over the last couple of days (in fact the above current prognosis section suggests this process may already be starting). I forecast dissipation of this system as a tropical cyclone by 72 hours when the forecast track takes it beneath the new upper vortex. I end the forecast after 72 hours as I question how favorable conditions will be after it passed the new upper vortex and catches up to the other upper vortex currently at 45W longitude. It is possible that by six days (144 hours) after the other upper vortex dissipates and this system reaches the waters northeast of the Lesser Antilles that it could finally encounter more favorable conditions and re-develop.

Thermodynamic Outlook for the Forecast Period...This tropical cyclone will pass over 27 to 28 deg C waters that will be supportive of tropical development.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 16)...Sheared 45 mph maximum sustained wind tropical storm centered at 18.6N-32.5W

48 Hr Forecast (0000Z Sep 17)...Sheared 35 mph maximum sustained wind tropical depression centered at 19.6N-37.5W

72 Hr Forecast (0000Z Sep 18)...Remnant low centered at 20.6N-42.5W

Track Forecast...Twelve is currently north of the previous track forecast once again per the above current prognosis. I have adjusted the forecast points northward accordingly...but have not increased the northward angle of the forecast track as latest observations suggest a more westward track is resuming.

Intensity Forecast...I have made no changes to the intensity forecast...and still forecast this system to dissipate as a tropical cyclone by 0000Z September 18.

Impact Forecast...Impact swath shows the development of a small area of tropical storm force winds where the above intensity forecast suggests this system will briefly reach tropical storm status.

2016 Atlantic Hurricane Season Birdseye Discussion #117

By: NCHurricane2009, 5:04 PM GMT on September 14, 2016

**This blog post was intended to be posted at 2:35 AM EDT this morning. However technical difficulties occurred during the upload process overnight.**

...WEDNESDAY SEPTEMBER 14 2016 2:35 AM EDT...
Gusty winds and heavy rain occurring over northeast Florida and southeast Georgia near and over the coast...heavy rain with possible flash flooding to spread across eastern Georgia and South Carolina over the next couple of days. While finding a small area of reduced wind shear...the surface trough that was over the western Bahamas has strengthened into Tropical Storm Julia while making landfall on the northeast Florida coast. See first special feature section for additional details on the newly-formed tropical storm. Visit www.nhc.noaa.gov for up to the minute lastest information on Julia.

Tropical Storm Ian continues to curve northward toward the open north-central Atlantic where it will transition into a strong non-tropical remnant gale. See second special feature section below for additional details on Ian. Visit www.nhc.noaa.gov for up to the minute latest information on Ian.

In addition to Tropical Storms Ian and Julia...see the following statements for two other areas of interest.

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic in the atmospheric features chart below. Satellite imagery shows that a tropical wave remains well-organized with cyclonic rotation while moving across the Republic of Cabo Verde. A cut-off upper vortex retrograding southwestward into the Atlantic tropics to the northwest of the tropical wave has formed. However the tropical wave is likely to stay collocated with the favorable upper anticyclone east of this upper vortex and tropical cyclone formation will be possible. See third special feature section below for additional details. Some gusty rain showers over the next day will be possible over the Republic of Cabo Verde as the tropical wave moves through.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. Satellite imagery suggests yet another vigorous tropical wave with a thick...curved...and strong thunderstorm band is moving across western Africa toward the Atlantic tropics. Upper-level winds are expected to remain favorable in the eastern tropical Atlantic with the persistence of the upper anticyclone that is currently helping the tropical wave to the west designated as area of interest #1 above. There is strong computer model support showing this wave developing in this environment...and therefore will upgrade this tropical wave to a special feature on this blog with a tropical cyclone formation forecast if this tropical wave becomes better organized while moving into the Atlantic.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM JULIA...
Current Prognosis...Previously the surface trough that was over the Bahamas was supressed by what was left of the upper trough associated with Hermine's non-tropical remnant. However after this upper trough dissipated...the surface trough produced strong thunderstorm activity whose latent heat release amplified upper ridging that was west of the upper trough. It was previously expected that the cut-off upper trough that is currently over the Gulf of Mexico (which was a part of the upper trough that is now supporting the 980 mb frontal cyclone over the north-central Atlantic) would unfavorably shear this surface trough...but instead the amplified upper ridging reduced the shear over the surface trough while also enhancing the surface trough's upper outflow. As a result while making landfall on the east coast of Florida...the surface trough has quickly strengthened into the tenth tropical storm of the 2016 Atlantic Hurricane Season...Julia. Prior to today...this system was expected to track more westward while steered by the 1023 mb ridge over the east US coast and 1028 mb ridge currently over the north-central US following behind. Instead Julia's initial motion is clearly northward due to steering provided by the cut-off upper trough in the Gulf of Mexico...which is more amplified due to the more amplified upper ridging over Julia. Also some of the northward motion may be being caused by the low-level ridge weakness between the 1023 mb and 1028 mb ridges...associated with the cold front extending from eastern Canada. Visible satellite animation during sunset and nighttime infrared after sunset suggests the center moved northward from 29.6N-81.3w at 2100Z to 30.1N-81.3W at 0000Z. However by 0300Z the northward motion appears to have slowed while the center has only reached 30.3N latitude. Heavy rain and some gusty winds are being reported near the center over northeastern Florida and southeastern Georgia.

Atmospheric Outlook for the Forecast Period...Over the next 24 hours the favorable upper ridging over Julia is likely to persist which may help Julia strengthen a little more...but by 48 hours the upper trough associated with the cold front extending from eastern Canada is expected to dig southward and intensify the unfavorable westerly vertical shear across Julia. The slowing northward track noted at the end of the above current prognosis section indicates that the low-level ridging to the north is beginning to have an influence on the steering of Julia. As the stronger 1028 mb ridge center over the north-central US moves directly north of Julia...the track is likely to become less to the north and more to the west over the next 48 hours.

Thermodynamic Outlook for the Forecast Period...Rather warm 31 deg C waters near the northeast Florida and Georgia coasts may help Julia strengthen a little more in the next 24 hours while Julia remains centered near the coast.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 15)...50 mph maximum sustained wind tropical storm centered over southeastern Georgia at 31.7N-81.3W

48 Hr Forecast (0000Z Sep 16)...35 mph maximum sustaiend wind tropical depression dissipating into remnant low...centered over eastern Georgia at 33N-82.8W

Track Forecast...The first 24 hours of my forecast track is based on the change in the central position between 0000Z and 0300Z noted in the above current prognosis...which is a rate of 0.2N latitude per 3 hours (or 1.6N latitude per 24 hours). My forecast track during this timeframe is east of the 11 PM EDT NHC forecast as the surface center may try to re-generate to the east toward the strongest offshore thunderstorm activity. The track is bent more westward by 48 hours per the above atmospheric outlook section.

Intensity Forecast...My intensity forecast is slightly higher than the 11 PM EDT NHC advisory for the next 24 hours due to continued favorable atmospheric and thermodynamic conditions outlined for this timeframe in the above atmo and thermo outlook sections. However by 48 hours...Julia should track further into land while dealing with higher levels of unfavorable westerly vertical shear which should cause its dissipation as a tropical cyclone.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track. The heavy rainfall statement in the above graphic does not include northeast Florida as latest doppler radar shows that most of the rain shield has exited Florida.

...SPECIAL FEATURE...TROPICAL STORM IAN...
Current Prognosis...Although Ian is producing a large and strong thunderstorm complex...the activity is pushed to the north of the surface center due to southerly vertical shear induced by the nearby upper vortex lying the northwest. This is preventing Ian from strengthening quickly. As of 0000Z the center of Ian passed over 27N-53W.

Atmospheric Outlook for the Forecast Period...Ian continues to move north-northwestward while steered by the cut-off upper vortex mentioned in the above current prognosis section. By 48 to 72 hours...the surface cold front and its upper trough currently over eastern Canada will move into the Atlantic and begin to accelerate the track of Ian in a northeastward direction. By 72 hours...Ian is likely to strengthen...but because it will be transitioning into a non-tropical remnant gale supported by divergence on the east side of the upper trough.

Thermodynamic Outlook for the Forecast Period...On the current forecast track...this system will be over 28 to 29 deg C waters supportive of tropical development for the first part of the forecast period...reaching waters well below 26 deg C by 72 hours which will help this system transition to non-tropical per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 15)...50 mph maximum sustained wind tropical storm centered at 31N-55W

48 Hr Forecast (0000Z Sep 16)...50 mph maximum sustained wind tropical storm centered at 39N-50W

72 Hr Forecast (0000Z Sep 17)...Non-tropical remnant gale centered at 52N-38W

Track Forecast...My updated track forecast is adjusted northward and northeastward due to the 0000Z fix in the current prognosis which is slightly north of the previous forecast...and to keep up with the latest computer model guidance which continues to show a faster acceleration to the northeast.

Intensity Forecast...Although Ian has been able to fire strong thunderstorm activity...satellite imagery continues to show that the center itself has no thunderstorm activity as Ian continues to struggle with wind shear. And with wind shear expected to continue for the next 48 hours...I forecast no additional strengthening of Ian as a tropical cyclone. However Ian could strengthen further by 72 hours and beyond as it transitions to non-tropical per the above atmopsheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track.

...SPECIAL FEATURE...TROPICAL WAVE INVEST 95-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...The tropical wave in the eastern tropical Atlantic continues to be well-organized with cyclonic rotation in its thunderstorm activity. Satellite animation suggests the center of rotation was over the southeastern islands of the Republic of Cabo Verde at 15N-23W as of 0000Z. Squalls of gusty rain showers will continue to pass over the islands over the next 24 hours. Because the 0000Z center fix was north of my previous forecast track...my updated forecast track listed below is a northward adjustment.

Atmospheric Outlook for the Forecast Period...Although a cut-off upper vortex retrograding southwestard into the Atlantic tropics has developed to the northwest of this tropical wave...wave will initially be collocated with a favorable upper anticyclone to the east of this upper vortex which will help its upper outflow and keep wind shear favorably low. However by 96 hours...conditions will become less favorable due to the warm core upper anticyclone currently in the central Atlantic being pumped up by Tropical Storm Ian's thunderstorm latent heat release. Relatively lower pressures between the upper anticyclone developing over this tropical wave and the central Atlantic anticyclone is expected to lead to the formation of another cut-off upper vortex which this tropical wave will have to pass under. Thus I show dissipation of this system back into a remnant low by 96 hours.

Thermodynamic Outlook for the Forecast Period...This tropical wave will pass over 28 to 29 deg C waters that will be supportive of tropical development.

24 Hr Forecast (0000Z Sep 15)...35 mph maximum sustained wind tropical depression centered at 16N-28W

48 Hr Forecast (0000Z Sep 16)...45 mph maximum sustained wind tropical storm centered at 17N-33W

72 Hr Forecast (0000Z Sep 17)...Sheared 35 mph maximum sustained wind tropical depression centered at 18N-38W

96 Hr Forecast (0000Z Sep 18)...Remnant low centered at 19N-43W

2016 Atlantic Hurricane Season Birdseye Discussion #116

By: NCHurricane2009, 7:28 AM GMT on September 13, 2016

...TUESDAY SEPTEMBER 13 2016 3:30 AM EDT...
The vigorous tropical wave in the central Atlantic has finally become Tropical Storm Ian. Ian is expected to curve northward and then northeastward into the open north Atlantic over the next few days...see first special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on Ian.

In addition to Tropical Storm Ian...see the following statements for two other areas of interest.

The following statement concerns area of interest #1 marked over the western tropical Atlantic over the western Bahamas and just east of Florida in the atmospheric featueres chart below. The surface trough in this area has finally re-organized into a surface low. However while tracking west-northwest into Florida and the southeastern United States...continued westerly vertical shear and land interaction should prevent tropical cyclone formation. However locally heavy rain with isolated flash flooding will be possible. This is my final statement on this surface low on this blog unless the National Hurricane Center continues to mention it in their tropical weather outlook.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. Satellite imagery shows that an organized tropical wave with cyclonic rotation has emerged from western Africa. The upper trough currently in the northeastern Atlantic...to the northwest of this tropical wave...is amplifying into a cut-off upper vortex that will retrograde southwestard into the Atlantic tropics. Therefore this tropical wave is likely to stay collocated with a favorable upper anticyclone to develop east of this upper vortex and tropical cyclone formation will be possible. See second special feature section below for additional details. Regardless of tropical cyclone formation or not...some gusty rain showers over the next day will be possible over the Republic of Cabo Verde in the eastern tropical Atlantic.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0136Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM IAN...
Current Prognosis...Vigorous tropical wave Invest 94-L in the central Atlantic has finally strengthened into Tropical Storm Ian this past afternoon. The thunderstorm activity associated with this system has expanded in size but remains pushed east of the center by southwesterly vertical shear induced by the nearby upper vortex lying to the northwest. As of 0000Z the center of Ian passed over 23N-51W.

Atmospheric Outlook for the Forecast Period...Ian continues to move north-northwestward while steered by the cut-off upper vortex mentioned in the above current prognosis section. By 72 to 96 hours...the 1004 mb frontal depression over eastern Canada and its upper trough will enter the Atlantic and begin to accelerate the track of Ian in a northeastward direction. By 96 hours...this system is likely to strengthen...but because it will be transitioning into a non-tropical remnant gale supported by divergence on the east side of the upper trough.

Thermodynamic Outlook for the Forecast Period...On the current forecast track...this system will be over 28 to 29 deg C waters supportive of tropical development for the first part of the forecast period...reaching waters well below 26 deg C by 96 hours which will help this system transition to non-tropical per the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 14)...45 mph maximum sustained wind tropical storm centered at 26N-53W

48 Hr Forecast (0000Z Sep 15)...45 mph maximum sustained wind tropical storm centered at 30N-55W

72 Hr Forecast (0000Z Sep 16)...45 mph maximum sustained wind tropical storm centered at 37N-52.5W

96 Hr Forecast (0000Z Sep 17)...Non-tropical remnant gale centered at 50N-39W

Track Forecast...Ian is slightly southeast of the previous forecast track and therefore I have adjusted the early part of the forecast track south and east accordingly. The later part of the forecast is adjusted north and east to keep up with the lastest computer model guidance which now shows a much faster acceleration to the northeast.

Intensity Forecast...Although Ian has been able to fire occasional storm bursts over its center...the most recent satellite imagery shows the center having no thunderstorm activity as Ian continues to struggle with wind shear. And with wind shear expected to continue for the next 72 hours...I forecast no additional strengthening of Ian as a tropical cyclone. However Ian could strengthen further by 96 hours and beyond as it transitions to non-tropical per the above atmopsheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track.

...SPECIAL FEATURE...TROPICAL WAVE INVEST 95-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...A well-organized tropical wave with cyclonic rotation in its thunderstorm activity has emerged from Africa into the eastern tropical Atlantic. Satellite animation suggests the center of rotation was located at 13N-18W to the east-southeast of the Repbulic of Cabo Verde. Satellite animation also suggests the tropical wave is moving at about 5W longitude per day...and the forecast track listed below is based on this initial motion.

Atmospheric Outlook for the Forecast Period...Although the upper trough in the northeast Atlantic is currently developing into a cut-off upper vortex that will retrograde southwestward into the Atlantic tropics...this tropical wave will initially be collocated with a favorable upper anticyclone to the east of this upper vortex which will help its upper outflow and keep wind shear favorably low. However by the end of the 120-hour forecast period...conditions will become less favorable due to the warm core upper anticyclone currently in the central Atlantic being pumped up by Tropical Storm Ian's thunderstorm latent heat release. Relatively lower pressures between the upper anticyclone developing over this tropical wave and the central Atlantic anticyclone is expected to lead to the formation of another cut-off upper vortex which this tropical wave will have to pass under. Thus I show dissipation of this system back into a remnant low at the end of the 120-hour forecast period.

Thermodynamic Outlook for the Forecast Period...This tropical wave will pass over 28 to 29 deg C waters that will help with tropical development.

24 Hr Forecast (0000Z Sep 14)...Tropical low centered just south of the Republic of Cabo Verde at 13.5N-23W

48 Hr Forecast (0000Z Sep 15)...35 mph maximum sustained wind tropical depression centered at 14.5N-28W

72 Hr Forecast (0000Z Sep 16)...45 mph maximum sustained wind tropical storm centered at 15.5N-33W

96 Hr Forecast (0000Z Sep 17)...Sheared 35 mph maximum sustained wind tropical depression centered at 16.5N-38W

120 Hr Forecast (0000Z Sep 18)...Remnant low centered at 17.5N-43W

2016 Atlantic Hurricane Season Birdseye Discussion #115

By: NCHurricane2009, 4:12 AM GMT on September 12, 2016

...MONDAY SEPTEMBER 12 2016 12:12 AM EDT...
The following statement concerns area of interest #1 marked over the western tropical Atlantic near the eastern Bahamas in the atmospheric featueres chart below. The surface trough in this area has not re-organized into a surface low as it approaches the Bahamas. The upper trough over the Bahamas...once associated with the non-tropical remnants of Hermine...is not weakenining fast enough and as a result this surface trough is likely to get suppressed from further developing by this upper trough. This is my final statement on this surface trough on this blog unless the National Hurricane Center continues to mention it in their tropical weather outlook.

The following statement concerns area of interest #2 marked over the central tropical Atlantic in the atmospheric features chart below. A strong tropical wave in this region continues to feature a large broad low pressure spin with strong thunderstorm activity. It remains possible that this system strengthens further into a tropical depression or tropical storm as it moves northward through the open Atlantic over the next few days. See special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #3 marked over the eastern tropical Atlantic in the atmospheric features chart below. Another vigorous tropical has emerged from western Africa and is passing over and south of the Republic of Cabo Verde in the eastern tropical Atlantic. Warm air advecdtion ahead of the 985 mb frontal cyclone over the eastern US and eastern Canada has amplified upper ridging across the north Atlantic...which in turn is equally causing the upper trough currently in the northeast Atlantic to amplify directly north of this tropical wave. This amplifying upper trough is pushing upper air toward the tropical wave and thus limiting its upper outflow...resulting in dissipation of most of the shower and thunderstorm activity. This is my final statement on this tropical wave on this blog.

The following statement concerns area of interest #4 marked over western Africa in the atmospheric features chart below. Satellite imagery shows that a tropical wave over western Africa is developing increasingly stronger and better organized thunderstorm activity while approaching the eastern tropical Atlantic. The upper trough currently in the northeastern Atlantic...to the northwest of this tropical wave...is expected to amplify into a cut-off upper vortex that retrogrades southwestard into the Atlantic tropics. Therefore this tropical wave is likely to stay collocated with a favorable upper anticyclone to develop east of this upper vortex as it moves into the Atlantic...and therefore will watch this tropical wave for any signs of additional development over the next few days.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 94-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...Vigorous tropical wave Invest 94-L in the central Atlantic continues to have a large cyclonic circulation. Although the thunderstorm activity has become concentrated and more organized in the east half of the circulation...the circulation itself appears to have become less organized...broadened...and perhaps taken a more westward track. Although its hard to define a precise center at the moment...it appears the broad circulation was centered at 19N-49W as of 0000Z earlier this evening.

Atmospheric Outlook for the Forecast Period...The nearby cut-off upper vortex lying to the northwest continues to steer this tropical wave north-northwestward into the open central Atlantic. By 48 to 72 hours as this system runs into the low-level Atlantic ridge the northward track is likely to slow down and bend a little more west. The updated forecast track listed below is adjusted westward when compared to the previous due to the observations noted in the above current prognosis...which now puts this system closer to the upper vortex. This will keep the unfavorable shear currently being imparted by the upper vortex at higher levels and thus the updated intensity forecast below now only shows this system becoming a tropical depression. However it is conceivable this system becomes a tropical storm if the broad circulation establishes a new center under or closer to the thunderstorm activity being sheared off to the east. At 96 to 120 hours...the frontal cyclone and upper trough currently over western Canada will enter the Atlantic from the United States and begin to accelerate the track of this system in a northeastward direction. At the end of the 120-hour forecast period...this system is likely to finally strengthen...but because it will be transitioning into a non-tropical remnant gale supported by divergence on the east side of the upper trough.

Thermodynamic Outlook for the Forecast Period...On the current forecast track...this system will be over 28 to 29 deg C waters supportive of tropical development for the first part of the forecast period...reaching waters below 26 deg C which will help this system transition to non-tropical at 120 hours per the above atmospheric outlook section.

24 Hr Forecast (0000Z Sep 13)...35 mph maximum sustained wind tropical depression centered at 24N-51.5W

48 Hr Forecast (0000Z Sep 14)...35 mph maximum sustained wind tropical depression centered at 28N-54W

72 Hr Forecast (0000Z Sep 15)...35 mph maximum sustained wind tropical depression centered at 31N-56.5W

96 Hr Forecast (0000Z Sep 16)...35 mph maximum sustained wind tropical depression centered at 36.5N-54W

120 Hr Forecast (0000Z Sep 17)...Non-tropical remnant gale centered at 45N-45W

2016 Atlantic Hurricane Season Birdseye Discussion #114

By: NCHurricane2009, 7:18 AM GMT on September 11, 2016

...SUNDAY SEPTEMBER 11 2016 3:20 AM EDT...
The following statement concerns area of interest #1 marked over western Cuba and southeastern Gulf of Mexico. The weak surface low that was over the Florida Keys has moves into the southeastern Gulf of Mexico but remains under northerly shear to the east of an upper anticyclone and to the west of the upper trough that was associated with Hermine's non-tropical remnants. As a result its thunderstorm activity is pushed to the south of the surface low and over western Cuba. Another area of thunderstorms with a surface trough has formed just west of this surface low while supported by divergence on the southeast side of the upper trough associated with the intensifying 998 mb frontal cyclone over the eastern US and eastern Canada. Upper westerlies from this upper trough are expected to overspread this surface low in the next 24 hours which will continue to shear apart this surface low. Therefore tropical cyclone formation is not expected from this surface low. This is my final statement on this surface low on this blog unless the National Hurricane Center continues to mention it in their tropical weather outlook.

The following statement concerns area of interest #2 marked over the western tropical Atlantic near the eastern Bahamas in the atmospheric featueres chart below. The surface trough in this area has not re-organized into a surface low as it approaches the Bahamas. The upper trough over the Bahamas...once associated with the non-tropical remnants of Hermine...is not weakenining fast enough and as a result this surface trough is likely to get suppressed from further developing by this upper trough. This is my final statement on this surface trough on this blog unless the National Hurricane Center continues to mention it in their tropical weather outlook.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. A strong tropical wave in this region continues to feature a large broad low pressure spin that is becoming increasingly more organized. Conditions remain favorable for the spin to organize further into a tropical depression or tropical storm over the next couple of days. See special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #4 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is emerging from Africa. As the 998 mb frontal cyclone over the eastern US and eastern Canada moves into the Atlantic and intensifies further...warm air advection ahead of the frontal cyclone will amplify upper ridging across the north Atlantic which in turn will equally cause the upper trough currently in the northeast Atlantic to amplify and become a cut-off upper vortex that retrogrades southwestward into the Atlantic tropics. It is likely this upper vortex will disrupt this tropical wave with unfavorable vertical shear and prevent additional development...and no computer models forecast this tropical wave to develop.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0134Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 94-L...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...The vigorous tropical wave in the central Atlantic continues to have a large cyclonic circulation. A more precise center in the large circulation appears to be becoming defined at 14.5N-45W as of 0000Z...and was moving northward into 15N-45W as of 0500Z. Thunderstorm activity around this center is becoming better organized and a tropical depression or tropical storm could form in the next 24 hours. This system is east of my previous forecast...and because it is already tracking northward I have shifted my updated forecast significantly eastward.

Atmospheric Outlook for the Forecast Period...Unlike my previous forecasts this system does not look like it will be shallow enough to take a more westward track under the influence of the low-level Atlantic ridge...as this system appears to have already developed a tall enough circulation to be steered more northward by the nearby cut-off upper vortex lying to the northwest. However by 72 to 96 hours as this system runs into the low-level ridge the northward track is likely to slow down and bend a little more west. The adjusted forecast track allows this system to stay further away from the upper vortex which will reduce the unfavorable shear from the upper vortex...and also the more northward track is aligned with the upper southerly flow on the east side of the upper vortex...another effect which will reduce the shear. Thus the intensity forecast listed below is raised when compared to the previous. The strengthening rate is slowed by 72 hours and some weakening is shown by 96 hours as this system gets closer to the upper vortex which will increase the shear. By the end of the 120 hour forecast period...a frontal cyclone currently over western Canada will enter the Atlantic from the United States and begin to accelerate the track of this system in a northeastward direction...with additional weakening likely as the upper trough of this frontal cyclone applies southwesterly shear. Just beyond the forecast period...this system may stop weakening and actually re-strengthen while transitioning into a non-tropical remnant gale supported by divergence on the east side of the upper trough.

Thermodynamic Outlook for the Forecast Period...On the updated forecast track...this system will be over 28 to 29 deg C waters supportive of tropical development for the first part of the forecast period...reaching cooler 27 to 26 deg C waters at the end of the forecast period.

24 Hr Forecast (0000Z Sep 12)...40 mph maximum sustained wind tropical storm centered at 19N-47.5W

48 Hr Forecast (0000Z Sep 13)...60 mph maximum sustained wind tropical storm centered at 24N-50W

72 Hr Forecast (0000Z Sep 14)...70 mph maximum sustained wind tropical storm centered at 28N-52.5W

96 Hr Forecast (0000Z Sep 15)...60 mph maximum sustained wind tropical storm centered at 31N-55W

120 Hr Forecast (0000Z Sep 16)...50 mph maximum sustained wind tropical storm centered at 36.5N-52.5W

2016 Atlantic Hurricane Season Birdseye Discussion #113

By: NCHurricane2009, 5:15 AM GMT on September 10, 2016

...SATURDAY SEPTEMBER 10 2016 1:30 AM EDT...
The following statement concerns area of interest #1 marked over Cuba and the Bahamas. The active northern portion of tropical wave Invest 92-L has intensified into a 1013 mb surface tropical low located between Cuba...the Bahamas...and south Florida while enhanced by divergent upper northerly flow between the west side of what's left of the upper trough that was associated with the non-tropical remnants of Hermine and east side of the upper anticyclone that was previously over the tropical wave. This surface low is being steered westward into the Gulf of Mexico by low-level ridging over the southeastern United States...with the surface low possibly wobbling more west-northwest in the next 24 hours in response to a ridge weakness to be created as the 1008 mb frontal cyclone over the central US moves into the eastern US...followed by a more westward track again by 48 hours after the frontal cyclone moves away. The cloud swirl of the surface low was seen moving across the Florida Keys while the thunderstorms are sheared off to the south due to the strong northerly upper flow...but on the above-mentioned track may encounter less shear while arriving beneath the upper anticyclone in the next 24 hours. However tropical cyclone formation is not likely as by 48 hours a vast region of upper westerlies in the wake of the frontal cyclone's upper trough will shear this system once again.

The following statement concerns area of interest #2 marked over the western tropical Atlantic near the northern Lesser Antilles and Virgin Islands in the atmospheric featueres chart below. The tropical low pressure spin in this area has not become better organized and has opened into a surface trough. While rounding the southwest side of the 1028 mb Atlantic ridge...this system is tracking west-northwestward into the western Atlantic and arriving beneath the south side of favorable western Atlantic upper ridging that was previously pumped up by the warm air advection on the east side of the remnant gale of Hermine. This favorable upper ridging will become re-enforced as the upper trough that was associated with Hermine's remnants diminishes and upper anticyclonic ridging over the eastern United States moves offshore. The CMC computer model continues to suggest tropical cyclone formation from this system while enhanced by this upper ridging. However it is also possible that while moving over or near the Bahamas...where the upper trough that was once associated with Hermine is currently located...that the upper trough does not dissipate fast enough which would ultimately disrupt this system from tropically developing.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. A strong tropical wave in this region continues to feature a large broad low pressure spin that is becoming increasingly more organized. Conditions remain favorable for the spin to organize further into a tropical depression or tropical storm over the next couple of days. See special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #4 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is emerging from Africa this evening. As the 1008 mb frontal cyclone over the central US moves into the Atlantic and intensifies...warm air advection ahead of the frontal cyclone will amplify upper ridging across the north Atlantic which in turn will equally cause the upper trough currently in the northeast Atlantic to amplify and become a cut-off upper vortex that retrogrades southwestward into the Atlantic tropics. It is likely this upper vortex will disrupt this tropical wave with unfavorable vertical shear and prevent additional development...and no computer models forecast this tropical wave to develop.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1926Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 94-L...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...A vigorous tropical wave with a large cyclonic circulation has moved from the eastern to central tropical Atlantic. The thunderstorm activity associated with the circulation continues to become better organized...and the forecast below assumes the circulation will organize further into a tropical cyclone in about 24 hours. As of 0000Z the center of circulation was located at 12.5N-42.5W which is slighlty southwest of my previous track forecast. Therefore the updated track forecast listed below is adjusted slightly southwestward accordingly.

Atmospheric Outlook for the Forecast Period...Conditions will initially be favorable for tropical development of the tropical wave while being beneath upper anticyclonic flow with low shear and enhanced upper outflow. By 48 hours and beyond...the tropical wave will encounter less favorable southwesterly vertical shear to be imparted by the east side of the nearby cut-off upper vortex lying to the northwest. By 96 hours the intensity forecast shows some weakening as this system catches up and runs into the upper vortex. Toward the end of the 120 hour forecast period...the upper vortex will have weakened...but re-strengthening of this system is not shown in the forecast as this system enters northerly vertical shear on the west side of the weakening upper vortex. The forecast track shows somewhat of a northward angle due to expected steering influence from the upper vortex. Even though the upper vortex shrinks and weakens at the end of the 120 hour forecast period...the forecast northward angle is increased due to a low-level ridge weakness to be caused by a cold front to move into the western Atlantic from the United States.

Thermodynamic Outlook for the Forecast Period...This tropical wave will pass over 29 to 31 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 11)...35 mph maximum sustained wind tropical depression centered at 14.5N-47.5W

48 Hr Forecast (0000Z Sep 12)...Sheared 40 mph maximum sustained wind tropical storm centered at 16.5N-52.5W

72 Hr Forecast (0000Z Sep 13)...Sheared 40 mph maximum sustained wind tropical storm centered at 18.5N-57.5W

96 Hr Forecast (0000Z Sep 14)...Sheared 35 mph maximum sustained wind tropical depression centered at 20.5N-62.5W

120 Hr Forecast (0000Z Sep 15)...Sheared 35 mph maximum sustained wind tropical depression centered at 24N-66W

2016 Atlantic Hurricane Season Birdseye Discussion #112

By: NCHurricane2009, 6:43 AM GMT on September 09, 2016

...FRIDAY SEPTEMBER 9 2016 2:45 AM EDT...
The following statement concerns area of interest #1 marked over the western Caribbean Sea and Bahamas. Tropical wave Invest 92-L has continued to become less organized while outrunning the favorable upper anticyclone that it was previously under...and will now experience less favorable southerly and westerly vertical shear on the north and west sides of the upper anticyclone. The most active weather that was at the north end of the tropical wave remains concentrated over the eastern Bahamas while supported by divergence on the east side of the upper trough associated with the non-tropical remnants of Hermine. However this upper trough is expected to continue to weaken and de-amplify which should cause this remaining activity to diminish with time. This is my final statement on this blog concerning tropical wave Invest 92-L.

The following statement concerns area of interest #2 marked over the central tropical Atlantic near the northern Lesser Antilles islands in the atmospheric featueres chart below. The tropical low pressure spin in this area was continuing to become better organized earlier but this evening has become less organized. While rounding the southwest side of the 1030 mb Atlantic ridge...this system is tracking west-northwestward into the northeastern Caribbean islands and western Atlantic and therefore could later arrive beneath favorable western Atlantic upper ridging that was previously pumped up by the warm air advection on the east side of the remnant gale of Hermine. This favorable upper ridging will become re-enforced as the upper trough associated with Hermine's remnants diminishes and upper anticyclonic ridging over the southeastern United States moves offshore. The CMC computer model continues to suggest tropical cyclone formation from this system while enhanced by this upper ridging. Therefore if this system avoids excess land interaction with the northeastern Caribbean islands and becomes better organized while entering the western Atlantic...I will be upgrading this system to a special feature on this blog with a tropical cyclone formation forecast.

The following statement concerns area of interest #3 marked over the eastern tropical Atlantic in the atmospheric features chart below. A strong tropical wave in this region continues to feature a large broad low pressure spin that is becoming increasingly more consolidated and better organized. Conditions remain favorable for the spin to organize further into a tropical cyclone over the next few days. See special feature section below for additional details on this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0147Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE INVEST 94-L...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...A vigorous tropical wave with a large cyclonic circulation continues to move across the eastern tropical Atlantic...with the circulation consolidating toward the stronger thunderstorm activity on the southwest side of the system. As a result the cyclonic circulation has relocated further west at 36W longitude as of 0000Z earlier this evening. Satellite animation from 0000Z to 0300Z suggests the circulation is centered along 11.5N to 12N latitude. The thunderstorm activity associated with the circulation is gradually becoming more concentrated and better organized...and the forecast below assumes it will take about one to two more days for the broad circulation to organize into a tropical cyclone.

Atmospheric Outlook for the Forecast Period...Conditions will initially be favorable for tropical development of the tropical wave while being beneath upper anticyclonic flow with low shear and enhanced upper outflow. By 48 hours and beyond...the tropical wave will encounter less favorable southwesterly vertical shear to be imparted by the east side of a cut-off upper vortex that has recently developed from the base of the upper trough currently in the northeastern Atlantic. Per the above current prognosis this system is consolidating further to the west and so the updated forecast track is adjsuted westward accordingly. The updated track now places this system closer to the cut-off upper vortex such that the shear is now expected to be stronger. This is why the updated intensity forecast listed below is lowered...with some weakening shown by 120 hours as the system catches up and runs into the upper vortex. It is also likely this upper vortex will impart somewhat of a northward bend in the track of this system during the forecast period...and at 120 hours and beyond the northward angle in the track is likely to continue or be increased by a low-level ridge weakness caused by a cold front to move into the western Atlantic from the United States.

Thermodynamic Outlook for the Forecast Period...This tropical wave will pass over 29 to 30 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 10)...Tropical low with better defined center at 13N-41W

48 Hr Forecast (0000Z Sep 11)...35 mph maximum sustained wind tropical depression centered at 15N-46W

72 Hr Forecast (0000Z Sep 12)...Sheared 40 mph maximum sustained wind tropical storm centered at 17N-51W

96 Hr Forecast (0000Z Sep 13)...Sheared 40 mph maximum sustained wind tropical storm centered at 19N-56W

120 Hr Forecast (0000Z Sep 14)...Sheared 35 mph maximum sustained wind tropical depression centered at 21N-61W

2016 Atlantic Hurricane Season Birdseye Discussion #111

By: NCHurricane2009, 4:14 AM GMT on September 08, 2016

...THURSDAY SEPTEMBER 8 2016 12:15 AM EDT...
The following statement concerns area of interest #1 marked over eastern Cuba and Jamaica. Although it appears land interaction with Haiti...Jamaica...and eastern Cuba has made tropical wave Invest 92-L become less organized...upper-level winds will remain favorable for this system to possibly develop as it moves into the Gulf of Mexico. Therefore expect vigorous weather (heavy rain and gusty winds) to spread into the remainder of Cuba...the Cayman Islands...and northern Yucatan peninsula over the next couple of days. Interests in the Gulf of Mexico should carefully watch this tropical wave in case it develops into a tropical storm this weekend. However upper-level winds will become less favorable for tropical development should this system approach the United States Gulf coast early next week which will help reduce impacts should development occurr. See the first special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #2 marked over the central tropical Atlantic in the atmospheric features chart below. The tropical wave currently in this area is leaving behind a 1012 mb low pressure spin. This low pressure spin remains well-defined and is gradually growing more thunderstorm activity while continuing to have its poleward upper outflow enhanced by the east side of the nearby westward-retrograding inverted upper trough. While rounding the southwest side of the 1033 mb Atlantic ridge...this system is tracking west-northwestward toward the northeastern Caribbean islands and western Atlantic and therefore could later arrive beneath a favorable western Atlantic upper anticyclone that has become pumped up by the warm air advection on the east side of the remnant gale of Hermine. Over the last couple of days the CMC computer model has suggested tropical cyclone formation from this system while enhanced by this upper anticyclone. Therefore if this system avoids excess land interaction with the northeastern Caribbean islands and becomes better organized while entering the western Atlantic...I will be upgrading this system to a special feature on this blog with a tropical cyclone formation forecast.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. The tropical wave in this region remains defined in satellite pictures while moving from the eastern to central tropical Atlantic. It appears to have moved west-southwestward toward a far south latitude...perhaps due to some steering influence from the large cyclonic circulation of the nearby tropical wave to the east currently designated as area of interest #4 in the atmospheric features chart below. This tropical wave is now too far south to develop a cyclonic circulation and therefore this is my final statement on this blog regarding this tropical wave.

The following statement concerns area of interest #4 marked over the eastern tropical Atlantic in the atmospheric features chart below. A strong tropical wave in this region continues to feature a large broad low pressure spin. Conditions remain favorable for the spin to organize further into a tropical cyclone over the next few days. See second special feature section below for additional details on this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1926Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...NORTH-CENTRAL CARIBBEAN TROPICAL WAVE INVEST 92-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...The active northern portion of tropical wave Invest 92-L has moved into eastern Cuba and Jamaica over the last 24 hours. The mid-level spin that was present in this activity yesterday is not present and therefore the tropical wave has become less organized. The updated intensity forecast listed below is lowered relative to the previous due to the reduced organization. Divergence on the southeast side of of the upper vortex associated with the remnant gale of Hermine is producing additional activity over the eastern half of the Bahamas with the moisture from the tropical wave. As of 0000Z the tropical wave axis was crossing 77.5W longitude.

Atmospheric Outlook for the Forecast Period...The favorable upper anticyclone over the tropical wave (which keeping shear favorably low and upper outflow favorably high) is expected to stay collocated with the tropical wave for the first 72 hours of the forecast period. A frontal cyclone moving into the eastern United States during the later part of the forecast period is likely to bend the track of this system northward and then northeastward at 72 to 96 hours. It is during this time this system will move into less favorable westerly shear on the north side of the aforementioned upper anticyclone. By 120 hours...this system will have missed the low-level ridge weakness associated with the frontal cyclone and begin to turn back westward in track. However any threat to the United States Gulf coast at 120 hours would be reduced as a large region of upper westerlies in the wake of the frontal cyclone's upper trough would continue to shear and perhaps weaken this system.

Thermodynamic Outlook for the Forecast Period...This system will be crossing rather favorable 30 to 31 deg C waters in the western Caribbean Sea and Gulf of Mexico.

24 Hr Forecast (0000Z Sep 9)...Tropical wave over and south of western Cuba at 82.5W longitude

48 Hr Forecast (0000Z Sep 10)...Tropical low forming over the southern Gulf of Mexico just north of the Yucatan at 22N-87W

72 Hr Forecast (0000Z Sep 11)...35 mph maximum sustained wind tropical depression over the eastern Gulf of Mexico 26N-87.5W

96 Hr Forecast (0000Z Sep 12)...45 mph maximum sustained wind sheared tropical storm centered just south of the Florida panhandle at 29N-85W

120 Hr Forecast (0000Z Sep 13)...Sheared remnant low centered just offshore of Alabama at 29.5N-88W

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE...
This special feature section is for area of interest #4 marked in the above atmospheric features chart.

Current Prognosis...A vigorous tropical wave with a large cyclonic circulation is moving across the eastern tropical Atlantic and Republic of Cabo Verde...with the wave axis slowing to a 5W longitude per 24 hour rate and only arriving to 25W longitude as of 0000Z earlier this evening. Therefore the updated forecast track listed below shows a slower westward track when compared to the previous. Satellite suggests the center of the broad cyclonic rotation is approximately at 12.5N latitude with the strongest thunderstorms to the southwest of the center at the moment. The forecast below assumes it will take about two to three moredays for the broad circulation to gradually organize into a tropical cyclone.

Atmospheric Outlook for the Forecast Period...Conditions will initially be favorable for tropical development of the tropical wave while being beneath upper anticyclonic flow with low shear and enhanced upper outflow. By 72 hours and beyond...the tropical wave will encounter less favorable southerly vertical shear to be imparted by the east side of a cut-off upper vortex to develop from the base of the upper trough currently in the northeastern Atlantic. However per the above current prognosis the updated forecast track shows a slower westward track...which means it will be further away from the cut-off upper vortex such that the shear is now expected to be only light. This is why the updated intensity forecast listed below now shows development into a tropical storm instead of just a tropical depression. It is also likely this upper vortex will impart somewhat of a northward bend in the track of this system by the later part of the forecast period.

Thermodynamic Outlook for the Forecast Period...This tropical wave will pass over 28 to 29 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 9)...Broad tropical low centered at 12.5N-30W

48 Hr Forecast (0000Z Sep 10)...Tropical low with better defined center at 13N-35W

72 Hr Forecast (0000Z Sep 11)...35 mph maximum sustained wind tropical depression centered at 15N-40W

96 Hr Forecast (0000Z Sep 12)...45 mph maximum sustained wind tropical storm centered at 17N-45W

120 Hr Forecast (0000Z Sep 13)...60 mph maximum sustained wind tropical storm centered at 19N-50W

2016 Atlantic Hurricane Season Birdseye Discussion #110

By: NCHurricane2009, 5:00 AM GMT on September 07, 2016

...WEDNESDAY SEPTEMBER 7 2016 1:01 AM EDT...
The following statement concerns area of interest #1 in the atmospheric features chart below. The remnant frontal gale of Hermine remains trapped offshore of the northeastern and mid-Atlantic United States due to the 1033 mb ridge over the northwestern Atlantic and 1024 mb ridge over the eastern United States. The gale and associated upper vortex remain vertically stacked over each other...with the gale continuing to weaken due to the non-divergent environment beneath the upper vortex. As such...the National Hurricane Center has issued their final advisory on the remnants of Hermine as the coastal sea and weather conditions have finally improved. The cold temperatures of the upper vortex have not induced enough instability for thunderstorms and transition of the remnant gale into a subtropical storm...and therefore this is my final statement on the remnants of Hermine on this blog.

The following statement concerns area of interest #2 marked over Haiti and the Dominican Republic in the atmospheric features chart below. Vigorous tropical wave Invest 92-L continues to show signs of organization while moving across this area...therefore expect vigorous weather (heavy rain and gusty winds) to spread into...Jamaica...Cuba...and Cayman Islands over the next few days. Interests in the Gulf of Mexico should carefully watch this tropical wave in case it develops into a tropical storm this weekend. However upper-level winds will become less favorable for tropical development should this system approach the United States Gulf coast early next week which will help reduce impacts should development occurr. See the first special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is currently in this region featuring a southern 1012 mb low pressure spin. It appears this low pressure spin will continue to have its poleward upper outflow enhanced by the east side of the nearby westward-retrograding inverted upper trough. Showers and thunderstorms are currently skeletal in nature but are well-organized and therefore will continue to watch this low pressure spin as it moves toward the Lesser Antilles and eastern Caribbean Sea over the next couple of days.

The following statement concerns area of interest #4 marked over the eastern tropical Atlantic in the atmospheric features chart below. The tropical wave in this region continues to show organization in its thunderstorms while moving into the waters southwest of the Republic of Cabo Verde. However its future is uncertain as it may get absorbed by or lose the battle for low-level inflow with the large broad low pressure spin of the nearby tropical wave to the east currently designated as area of interest #5 in the atmospheric features chart below.

The following statement concerns area of interest #5 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. A strong tropical wave has entered the eastern Atlantic from western Africa while developing a large broad low pressure spin. There is strong computer model support showing this tropical wave developing into a tropical cyclone and the 5-day odds for development in the latest National Hurricane Center tropical weather outlook is high. See second special feature section below for additional details on this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1918Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...HISPANIOLA TROPICAL WAVE INVEST 92-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...It appears the active northern portion of tropical wave Invest 92-L became pulled northward into Hispaniola (Haiti and the Dominican Republic) in the last 24 hours due to the ridge weakness associated with the remnant gale of Hermine in the western Atlantic. Satellite animation suggests a somewhat organized mid-level spin with thunderstorms over Hispaniola. As of 0000Z this tropical wave was crossing 71W longitude.

Atmospheric Outlook for the Forecast Period...The favorable upper anticyclone over the tropical wave (which keeping shear favorably low and upper outflow favorably high) is expected to stay collocated with the tropical wave for the first 96 hours of the forecast period. It was previously expected that a frontal cyclone moving into the eastern United States at the end of the forecast period (96 to 120 hours) would be too far north to influence the track of this system...but with the northward adjustment in the initial position (per the above current prognosis) and forecast track it is now expected this system will bend northward and then northeastward toward the low-level ridge weakness associated with this frontal cyclone at 96 to 120 hours. It is during this time this system will move into less favorable westerly shear on the north side of the aforementioned upper anticyclone. Just beyond 120 hours...this system will have missed the low-level ridge weakness associated with the frontal cyclone and begin to turn back westward in track. However any threat to the United States Gulf coast beyond 120 hours would be reduced as a large region of upper westerlies in the wake of the frontal cyclone's upper trough would continue to shear and perhaps weaken this system.

Thermodynamic Outlook for the Forecast Period...This system will be crossing rather favorable 30 to 31 deg C waters in the Caribbean Sea and Gulf of Mexico. Therefore my updated forecast listed below shows quick development into a tropical storm by 96 hours...but then shows slower development by 120 hours due to less favorable westerly shear per the above atmospheric outlook section.

24 Hr Forecast (0000Z Sep 8)...Tropical wave with mid-level rotation over eastern Cuba at 76W longitude

48 Hr Forecast (0000Z Sep 9)...Tropical wave with mid-level rotation centered just south of central Cuba...at 81W longitude

72 Hr Forecast (0000Z Sep 10)...Tropical wave with mid-level rotation reaching the surface near the western tip of Cuba at 22N-85.5W

96 Hr Forecast (0000Z Sep 11)...45 mph maximum sustained wind tropical storm over the eastern Gulf of Mexico 25N-87.5W

120 Hr Forecast (0000Z Sep 12)...60 mph maximum sustained wind sheared tropical storm over the northeastern Gulf of Mexico at 28N-85W

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE...
This special feature section is for area of interest #5 marked in the above atmospheric features chart.

Current Prognosis...A vigorous tropical wave has moved from 12.5W to 20.5W longitude while emerging from western Africa and into the eastern tropical Atlantic over the last 24 hours. Satellite animation suggests the cloud pattern has gone from a north-south axis of strong thunderstorms to a broad cyclonic gyre with the strongest thunderstorms east of the gyre center and still over the west coast of Africa. Satellite suggests the gyre center is approximately at 12.5N latitude. The forecast below is initially based on the 8W longitude per 24 hour current pace of the tropical wave...and assumes it will take about three to four days for the broad gyre to gradually organize into a tropical cyclone.

Atmospheric Outlook for the Forecast Period...Conditions will initially be favorable for tropical development of the tropical wave while being beneath upper anticyclonic flow with low shear and enhanced upper outflow. However by 72 to 120 hours...the tropical wave will encounter less favorable southwesterly vertical shear to be imparted by the east side of a cut-off upper vortex to develop from the base of the upper trough currently in the north-central Atlantic. This is why in my forecast listed below I do not show development beyond tropical depression strength. It is also likely this upper vortex will impart somewhat of a northward bend in the track of this tropical wave by the later part of the forecast period.

Thermodynamic Outlook for the Forecast Period...This tropical wave will pass over 28 to 29 deg C waters supportive for tropical development.

24 Hr Forecast (0000Z Sep 8)...Broad tropical low centered at 12.5N-28.5W

48 Hr Forecast (0000Z Sep 9)...Broad tropical low centered at 13N-36.5W

72 Hr Forecast (0000Z Sep 10)...Tropical low with better defined center at 14N-42W

96 Hr Forecast (0000Z Sep 11)...Sheared 35 mph maximum sustained wind tropical depression centered at 17N-48W

120 Hr Forecast (0000Z Sep 12)...Sheared 35 mph maximum sustained wind tropical depression centered at 20N-54W

2016 Atlantic Hurricane Season Birdseye Discussion #109

By: NCHurricane2009, 5:30 AM GMT on September 06, 2016

...TUESDAY SEPTEMBER 6 2016 1:30 AM EDT...
The following statement concerns area of interest #1 in the atmospheric features chart below. The remnant frontal gale of Hermine remains trapped offshore of the northeastern and mid-Atlantic United States due to the 1032 mb ridge over the northwestern Atlantic and 1024 mb ridge over the eastern United States. The gale and associated upper vortex have whirled toward each other and have become vertically stacked...but there are no signs of the cold temperatures of the upper vortex creating enough instability for thunderstorms and subtropical cyclone formation from this gale. The gale will be trapped stationary offshore of the US mid-Atlantic coast for about four more days...but because the gale is no longer beneath the upper divergent region east of the upper vortex it will now begin to weaken. Therefore an improvement of the coastal sea and weather conditions can be expected during the next couple of days.

The following statement concerns area of interest #2 marked over Lesser Antilles and eastern Caribbean Sea in the atmospheric features chart below. Vigorous tropical wave Invest 92-L continues to show signs of organization while moving into and across the eastern Caribbean Sea and tropical cyclone formation remains possible over the next few days. Expect vigorous weather (heavy rain and gusty winds) to spread into Haiti...the Dominican Republic...Jamaica...southeastern Cuba...and Cayman Islands over the next few days. Interests in the Yucatan peninsula of southeastern Mexico should carefully watch this tropical wave in case it develops into a tropical storm before landfall later this week. See special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is currently in this region featuring a low pressure spin at the north end of the wave and a large region of thunderstorms with a second low pressure spin to the south. The northern low pressure spin has become less organized and is no longer capable of developing into a tropical cyclone as vertical shear will increase while the base of the upper trough currently over the north-central Atlantic overspreads it. Meanwhile will continue to watch the southern low pressure spin over the next few days to see if the nearby inverted upper trough to the west suppresses it or if the east side of the inverted upper trough will continue to enhance its poleward upper outflow.

The following statement concerns area of interest #4 marked over the eastern tropical Atlantic in the atmospheric features chart below. The tropical wave in this region has seen an increase in the intensity and organization of its thunderstorm activity while passing south of the Republic of Cabo Verde while moving into more favorable upper anticyclonic flow with low shear and good upper outflow. However the latest computer model runs suggest yet another vigorous tropical wave to the east which is about to emerge from Africa may absorb this tropical wave...see statement on area of interest #5 below for additional details.

The following statement concerns area of interest #5 marked over western Africa in the atmospheric features chart below. Satellite imagery suggests a tropical wave approaching the eastern tropical Atlantic has seen a signficant increase in showers and thunderstorms. The latest CMC and European (ECMWF) model runs suggest this tropical wave will absorb the nearby tropical wave to the west (area of interest #4) and develop into a tropical cyclone while supported by favorable upper anticyclonic flow with low shear and good upper outflow. Any strong and sufficiently tall tropical cyclone that develops over the next few days will track northwestward into the open Atlantic while feeling the upper-level ridge weakness to be caused by the upper trough currently in the north-central Atlantic as the base of the upper trough continues amplifying southward.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1948Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...EASTERN CARIBBEAN TROPICAL WAVE INVEST 92-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...While moving into and across the eastern Caribbean Sea...this past afternoon's visible satellite imagery suggested tropical wave Invest 92-L lacks a closed surface circulation and is an open tropical wave at the moment based on low-level cloud motions. Showers and thunderstorms are concentrated across the northern half of the tropical wave...although there are times when this activity intermittenly dwindles. Any rotation that is seen in this activity at the moment perhaps is likely mid-level. As of 0000Z the tropical wave was at 67.5W longitude. Based on this system being an open wave...I have significantly lowered the intensity forecast and delayed forecast tropical cyclone formation till the 72 to 96 hour timeframe.

Atmospheric Outlook for the Forecast Period...The upper vortex to the west of the tropical wave (currently near Jamaica) will continue to retrograde westward...which will allow the upper anticyclone over the tropical wave (which keeping shear favorably low and upper outflow favorably high) to stay collocated with the wave through the forecast period. In fact the favorable upper anticyclone is expected to grow while the less favorable upper vortex diminishes. The ridge weakness associated with Hermine's remnant gale is not expected to bend the track of this tropical wave northward as the gale will weaken from this point forward. And at the end of the 120-hour forecast period...when this tropical wave crosses the Yucatan peninsula and enters the southern Gulf of Mexico...a frontal cyclone and upper trough moving into the eastern United States at this time is forecast to be too far north to bend the track of this system northward.

Thermodynamic Outlook for the Forecast Period...This system will be crossing rather favorable 30 to 31 deg C waters in the Caribbean Sea and Bay of Campeche in the southern Gulf of Mexico. Therefore my updated forecast listed below shows quick development into a tropical storm before landfall in the Yucatan due to these warm waters and favorable upper anticyclone mentioned in the above atmospheric outlook section.

24 Hr Forecast (0000Z Sep 7)...Tropical wave in the central Caribbean at 72.5W longitude

48 Hr Forecast (0000Z Sep 8)...Tropical wave in the central Caribbean at 77.5W longitude

72 Hr Forecast (0000Z Sep 9)...Tropical low in the western Caribbean centered to the southwest of the Cayman Islands at 17.5N-82.5W

96 Hr Forecast (0000Z Sep 10)...50 mph maximum sustained wind tropical storm making landfall on the east coast of the Yucatan peninsula at 18.5N-87.5W

120 Hr Forecast (0000Z Sep 11)...35 mph maximum sustained wind tropical depression over the eastern Bay of Campeche at 19.5N-92.5W

2016 Atlantic Hurricane Season Birdseye Discussion #108

By: NCHurricane2009, 5:42 AM GMT on September 05, 2016

...MONDAY SEPTEMBER 5 2016 1:45 AM EDT...
The following statement concerns area of interest #1 in the atmospheric features chart below. The remnant frontal gale of Hermine remains trapped offshore of the northeastern and mid-Atlantic United States due to the 1026 mb ridge over the northeastern US and northwestern Atlantic. The gale has produced an upper vortex over the northeastern US while its west side continues to pull down cooler air...with strong upper air divergence on the east side of the upper vortex allowing the gale to maintain strength. The gale will be trapped stationary offshore of the US mid-Atlantic coast for about five more days in between a western ridge to be supported by covergence west of the upper vortex and 1026 mb ridge as it moves to the gale's northeast. During the next 24 hours...the gale will become vertically stacked with the upper vortex...and combined with the south side of its circulation being over 26 deg C waters enough instability may occur for the re-development of thunderstorms over the gale center and the transition to subtropical storm status. Waiting to see the state of the gale as it becomes stacked with the upper vortex before declaring it a special feature with a subtropical cyclone forecast. After 24 hours...both the gale and upper vortex are expected to weaken which will cause an improvement of the coastal sea and weather conditions.

The following statement concerns area of interest #2 marked over Lesser Antilles and eastern Caribbean Sea in the atmospheric features chart below. Vigorous tropical wave Invest 92-L continues to become better oraganized while moving into the eastern Caribbean Sea and tropical cyclone formation remains possible over the next few days. Expect vigorous weather (heavy rain and gusty winds) in the Lesser Antilles...Virgin Islands...and Puerto Rico as the tropical wave crosses these islands in the next 24 hours. Interests elsewhere in the northern Caribbean islands (Haiti...the Dominican Republic...Jamaica...the Cayman Islands...and Cuba) and Yucatan peninsula of southeastern Mexico should carefully watch this tropical wave. See special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #3 marked over the centraltropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is currently in this region featuring a low pressure spin at the north end of the wave and a large region of thunderstorms to the south. The low pressure spin at the north end of the wave has seen an increase in thunderstorms and has become better defined tonight while becoming enhanced by divergence on the east side of a westward-retrograding upper vortex in the central Atlantic and it may develop into a short-lived tropical cyclone. See second special feature section below for additional details. Meanwhile will continue to watch the remainder of the tropical wave over the next few days to see if the aforementioned upper vortex suppresses it or if the east side of the upper vortex will enhance its poleward upper outflow.

The following statement concerns area of interest #4 marked over the eastern tropical Atlantic in the atmospheric features chart below. The tropical wave that recently emerged from western Africa remains largely inactive. However as it continues westward across the tropical Atlantic..it will move into more favorable upper anticyclonic flow with low shear and good upper outflow and possibly develop. Currently the CMC...GFS...and Euro (ECMWF) computer models suggest this tropical wave will develop at some point while moving across the Atlantic tropics and therefore will continue to watch this tropical wave over the next few days as well.

The following statement concerns area of interest #5 marked across the Gulf of Mexico. The surface troughs in the area have dissipated and the showers and thunderstorms have weakened. Although some favorable upper anticyclonic ridging has developed in the northern Gulf over the last 24 hours...this ridging is expected to shift northward into the United States due to warm air advection ahead of frontal cyclones moving across the northwestern US...which will later result in upper convergence on the southeast side of the upper ridging that will further suppress this activity in the Gulf. Therefore this is my final statement on this disturbance on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...LESSER ANTILLES TROPICAL WAVE INVEST 92-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...Tropical wave Invest 92-L continues to become gradually better organized while developing a circular area of thunderstorms over and north of the center of circulation. As of 0000Z earlier this evening the low pressure circulation was moving into the Lesser Antilles and eastern Caribbean Sea while centered at 15N-60.5W.

Atmospheric Outlook for the Forecast Period...The inverted upper trough to the west of the tropical wave will continue to retrograde westward...which will allow the upper anticyclone located in relatively higher pressures southeast of this trough (which is keeping the vertical shear favorably low and upper outflow favorably high for development) to stay collocated with the tropical wave. In fact the favorable upper anticyclone is expected to grow while the less favorable inverted upper trough diminishes. It previously appeared this tropical wave would run into the east side of the inverted upper trough in 24 hours...however the tropical wave has not progressed as fast to the west and therefore should stay beneath the favorable upper anticyclone during the entire forecast period. Also because the tropical wave has not progressed as fast to the west...it appears it will not interact with the low-level ridge weakness associated with Hermine's remnant gale to the northwest before this weakness diminishes...nor interact with an upper vortex to cut-off and retrograde into the Gulf of Mexico from the upper trough associated with the remnant gale should this system become a strong-tall tropical cyclone to be influenced by the upper vortex. Thus the updated forecast track listed below only shows this system lifting a little northward in the next 24 hours toward the remant gale of Hermine...afterwards the updated forecast track is generally south of the previous as the low-level weakness associated with the remnant gale diminshes. Despite the improved forecast with this tropical wave staying collocated with the favorable upper anticyclone...the slightly more north 0000Z center fix in the current prognosis and aforementioned northward lean in the 24-hour forecast track suggests more land interaction with Haiti and so I have slighlty lowered the intensity forecast in anticipation of this land interaction.

Thermodynamic Outlook for the Forecast Period...This system will be crossing rather favorable 30 to 31 deg C waters in the Caribbean Sea. Therefore if atmospheric conditions become favorable per the above atmospheric outlook section...this system could signficantly strengthen.

24 Hr Forecast (0000Z Sep 6)...35 mph maximum sustained wind tropical depression in the northeastern Caribbean Sea just south of Puerto Rico at 17N-66.5W

48 Hr Forecast (0000Z Sep 7)...40 mph maximum sustained wind tropical storm over southern Haiti centered at 18N-72.5W

72 Hr Forecast (0000Z Sep 8)...65 mph maximum sustained wind tropical storm centered between Jamaica and Cuba at 19N-77.5W

96 Hr Forecast (0000Z Sep 9)...85 mph maximum sustained wind hurricane centered in the northwestern Caribbean Sea west of the Cayman Islands and south of western Cuba at 20N-82.5W

120 Hr Forecast (0000Z Sep 10)...100 mph maximum sustained wind hurricane centered over the northeastern Yucatan peninsula at 21N-87.5W

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL LOW...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...The tropical low at the north end of the vigorous tropical wave that has recently moved from the eastern to central tropical Atlantic has seen an increase in thunderstorm activity and has become better defined while becoming supported by divergence on the east side of a cut-off upper vortex in the central Atlantic. As of 0000Z infrared satellite suggested the center of the tropical low was at 21N-35.5W...and appeared to be consolidating toward the southwest edge of a thunderstorm burst at 22N-36W as of 0300Z. The increasing thunderstorm activity is lopsised to the northeast of the tropical low center due to southwesterly vertical shear imparted by the aforementioned upper vortex.

Atmospheric Outlook for the Forecast Period...The northwest track of the tropical low is expected to bend increasingly westward in the next 48 hours as the ridge weakness associated with the 977 mb north-central Atlantic frontal cyclone becomes repalced by the 1026 mb ridge over the northeastern US as this ridge moves across the Atlantic. Also during this time...the vertical shear is expected to become more westerly and stronger as the southwest side of the strong upper trough associated with the 977 mb frontal cyclone overspreads this tropical low. Thus any tropical cyclone that develops from this tropical low is not likely to survive beyond 48 hours.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 deg C waters. Although this tropical low was previously suppressed by dry saharan air in the central Atlantic...recently upper divergence on the east side of an upper vortex (per the above current prognosis) has helped this tropical low to develop thunderstorms and mix out some of this dry air. Therefore tropical cyclone formation is becoming more likely.

24 Hr Forecast (0000Z Sep 6)...35 mph maximum sustained wind tropical depression centered at 24N-38W

48 Hr Forecast (0000Z Sep 7)...Remnant low centered at 25.2N-42W

2016 Atlantic Hurricane Season Birdseye Discussion #107

By: NCHurricane2009, 5:48 AM GMT on September 04, 2016

...SUNDAY SEPTEMBER 4 2016 1:50 AM EDT...
The following statement concerns area of interest #1 in the atmospheric features chart below. While merging with the tail end of the cold front of the 986 mb frontal cyclone and upper trough moving across the north Atlantic...Hermine transitions into a strengthening remnant frontal gale offshore of the mid-Atlantic and northeastern United States and thus gusty winds and sea swells continue to affect the coast in this area. The 1025 mb ridge north of the remnant gale...supported by convergence on the back side of the upper trough...has blocked it from continuing northeastward and it is beginning to stall. The gale will continue to pull cooler air associated with the tail end of the upper trough southward which in turn will cause the upper trough tail to amplify into a cut-off upper vortex. Intensifying upper air divergence on the east side of the amplifying cut-off will cause the gale to maintain strength while intensifying convergence on the west side of the cut-off causes another surface ridge to form west of of the gale. Therefore the gale will be trapped stationary offshore of the US mid-Atlantic coast for about six more days in between the western ridge and 1025 mb ridge as it moves to the gale's northeast. During the first two of the six days...the gale will become vertically stacked with the forecast cold core cut-off upper vortex...and combined with the south side of its circulation being over 26 deg C waters enough instability may occur for the re-development of thunderstorms over the gale center and the transition to subtropical storm status. Waiting to see the state of the gale as it becomes stacked with the upper vortex before declaring it a special feature with a subtropical cyclone forecast. After two days...both the gale and upper vortex are expected to weaken which will cause an improvement of the coastal sea and weather conditions.

The following statement concerns area of interest #2 marked in the atmospheric features chart below. As expected Gaston weakens into a remnant low while moving away from the Azores in the northeastern Atlantic...and is becoming absorbed by the 986 mb frontal cyclone moving across the north Atlantic. This is my final statement on Gaston on this blog.

The following statement concerns area of interest #3 marked over the central tropical Atlantic in the atmospheric features chart below. Vigorous tropical wave Invest 92-L continues to become better oraganized while approaching the Caribbean Sea and tropiacl cyclone formation is possible over the next few days. Expect vigorous weather (heavy rain and gusty winds) in the Lesser Antilles...Virgin Islands...and Puerto Rico as the tropical wave crosses these islands in the next 24 hours. Interests elsewhere in the northern Caribbean islands (Haiti...the Dominican Republic...Jamaica...the Cayman Islands...and Cuba) should carefully watch this tropical wave. See special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #4 marked over the eastern tropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is currently in this region featuring a low pressure spin west of the Republic of Cabo Verde and a large region of thunderstorms to the south. The low pressure spin meanwhile remains inactive due to dry saharan air to the north...and a portion of an eastern Atlantic cut-off upper trough to its immediate northwest has fractured into a westward retrograding upper vortex. It is not clear if this tropical wave will be suppressed by the upper vortex or if the east side of the upper vortex will enhance its poleward upper outflow. Therefore the potential of tropical development from this tropical wave remains uncertain.

The following statement concerns area of interest #5 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Yet another vigorous tropical wave is emerging from Africa and into the eastern tropical Atlantic...but its thunderstorm activity has diminished due to an eastern Atlantic upper trough to its immediate northwest which is suppressing its upper outflow by pushing upper-level air toward the tropical wave. However as it continues westward across the tropical Atlantic..it will move into more favorable upper anticyclonic flow with low shear and good upper outflow and possibly develop. Currently the CMC...GFS...and Euro (ECMWF) computer models suggest this tropical wave will develop at some point while moving across the Atlantic tropics and therefore will continue to watch this tropical wave over the next few days as well.

The following statement concerns area of interest #6 marked across the Gulf of Mexico. In the wake of Hermine...surface pressures across the Gulf of Mexico...southeastern Mexico..and adjacent eastern Pacific waters are low perhaps as the broad circulation of Hermine and broad parent tropical wave of Hermine which entered the eastern Pacific at the end of August have left behind low pressure areas. Showers and thunderstorms have increased across the Gulf of Mexico in this low pressure region due to split flow upper divergence between the southerlies ahead of Hermine's remnant gale upper trough and northerlies ahaead of an inverted upper trough in the western Caribbean Sea. The inverted upper trough in the western Caribbean is expected to weaken and while the upper trough associated with Hermine's remnant gale moves northeastward and away...allowing for a favorable upper anticyclone to develop over the Gulf in the next 24 hours. However this upper anticyclone is expected to shift northward into the United States due to warm air advection ahead of frontal cyclones moving across the northwestern US...later resulting in upper convergence on the southeast side of the upper anticyclone that will suppress this disturbance from developing in the Gulf.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1927Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 92-L...
This special feature section is for area of interest #3 marked in the above atmospheric features chart.

Current Prognosis...Tropical wave Invest 92-L in the central tropical Atlantic continues to see an increase in the intensity and organization of the thunderstorm activity as it nears the Lesser Antilles and eastern Caribbean Sea this evening. However the low pressure spin associated with the tropical wave appears to have become elongated east to west and so it is difficult to pinpoint the exact center of circualtion. I esimate that it was centered at 14N-55W as of 0000Z earlier this evening.

Atmospheric Outlook for the Forecast Period...The inverted upper trough to the west of the tropical wave will continue to retrograde westward...which will allow the upper anticyclone located in relatively higher pressures southeast of this trough (which is keeping the vertical shear favorably low and upper outflow favorably high for development) to stay collocated with the tropical wave. In fact the favorable upper anticyclone is expected to grow while the less favorable inverted upper trough diminishes. There is a possiblity this tropical wave will run into the east side of the inverted upper trough at 48 hours which will cause some light southerly vertical shear. Thus in the forecast listed below I slow the development of this system around 48 hours. However after that time...this system should slow its westward pace and begin bending northward in track in response to a ridge weakness caused by the remnant of Hermine and its upper trough...which will increase the distance betweeen this system and still-retrograding inverted upper trough...resulting in a reduction in shear over this system. Thus the development rate is increased again towards the later part of the forecast period (72 to 120 hours). Even though the low-level ridge weakness associated with Hermine's remnant gale should diminish as it moves north and weakens....the tail end of the upper trough associated with Hermine is expected to develop into an upper vortex retorgrading southwestward across the western Gulf of Mexico...and thus my 120 hour forecast assumes this system is a strong-tall tropical cyclone to still be tugged northward in the westward track by the upper vortex.

Thermodynamic Outlook for the Forecast Period...This system will enter rather favorable 30 to 31 deg C waters across the Caribbean Sea by the end of the forecast period. Therefore if atmospheric conditions become favorable per the above atmospheric outlook section...this system could signficantly strengthen.

24 Hr Forecast (0000Z Sep 5)...Tropical low just below tropical depression strength in the eastern Caribbean Sea...centered at 14.5N-63W

48 Hr Forecast (0000Z Sep 6)...35 mph maximum sustained wind tropical depression under light southerly shear just south of Haiti and the Dominican Republic centered at 16.5N-69W

72 Hr Forecast (0000Z Sep 7)...50 mph maximum sustained wind tropical storm centered between Haiti and Jamaica at 18N-75W

96 Hr Forecast (0000Z Sep 8)...75 mph maximum sustained wind hurricane centered over the Cayman Islands at 20N-80.5W

120 Hr Forecast (0000Z Sep 9)...90 mph maximum sustained wind hurricane centered over the western tip of Cuba at 22N-85W

2016 Atlantic Hurricane Season Birdseye Discussion #106

By: NCHurricane2009, 5:16 AM GMT on September 03, 2016

...SATURDAY SEPTEMBER 3 2016 1:17 AM EDT...
Hermine has weakened to a tropical storm after making landfall across north Florida...Georgia...and Carolinas. However Hermine is expected to re-strengthen as a non-tropical remnant frontal gale while stalling offshore of the United States mid-Atlantic coast...with gusty winds and sea swells possible along this coast over the next week. There is also the possiblity Hermine's remnant transitions into a subtropical storm during the next week. See first special feature section below for additional details on Hermine. Visit www.nhc.noaa.gov for up to the minute latest information on Hermine.

Gaston rapidly weakens to a minimal tropical storm while moving across the Azores due to cooler waters and upper-level convergence..and should dissipate into a remnant low at any time. See second special feature section below for additional details on Gaston. Visit www.nhc.noaa.gov for up to the minute latest information on Gaston.

In addition to our two active tropical cyclones...there are three other areas of interest...see the following statements...

The following statement concerns area of interest #1 marked over the central tropical Atlantic in the atmospheric features chart below. Vigorous tropical wave Invest 92-L has overcome dry air suppression due to favorable atmospheric dynamics. Specifically the east side of the inverted upper trough to the west is enhancing the poleward upper outflow...and a small upper anticyclone is forming over the tropical wave in relatively higher pressures to the southeast of the inverted upper trough. This small upper anticyclone is also enhancing the upper outflow in all directions and keeping the vertical shear over the tropical wave favorably low for tropical development. Because the inverted upper trough will continue to retrograde westward and away while weakening...this upper air pattern is expected to continue and thus chances once again are increasing that this tropical wave will develop. Therefore interests in the Lesser Antilles and northern Caribbean islands (Virgin Islands...Puerto Rico...Haiti...the Dominican Republic...Jamaica...the Cayman Islands...and Cuba) should carefully watch this tropical wave. See third special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. Another vigorous tropical wave is currently in this region featuring a low pressure spin over the Republic of Cabo Verde and a large region of thunderstorms to the south. The low pressure spin meanwhile is inactive due to ingestion of dry saharan air to the north...and a portion of an eastern Atlantic cut-off upper trough to its immediate northwest is expected to fracture into a westward retrograding upper vortex. It is not clear if this tropical wave will be suppressed by the upper vortex or if the east side of the upper vortex will enhance its poleward upper outflow. Therefore the potential of tropical development from this tropical wave remains uncertain.

The following statement concerns area of interest #3 marked over western Africa in the atmospheric features chart below. Yet another vigorous tropical wave is seen on satellite pictures moving into west Africa from central Africa over the last day. As it emerges into the eastern tropical Atlantic...it may get initially suppressed by a portion of an eastern Atlantic cut-off upper trough to its northwest...after which time it will move into more favorable upper anticyclonic flow with low shear and good upper outflow and develop. Currently the CMC...GFS...and Euro (ECMWF) computer models suggest this tropical wave will develop at some point while moving across the Atlantic tropics and therefore will continue to watch this tropical wave over the next few days as well.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1926Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM HERMINE...
Current Prognosis...Hermine has weakened to a tropical storm after making landfall across north Florida...Georgia...and Carolinas. However this evening the weakening has stopped with Hermine maintaining maximum sustained winds of 50 mph. This is due to supportive upper divergence on the east side of the upper trough associated with the surface cold front Hermine is moving into. Where the surface convergence is maximum along the cold front and upper divergence is maximum along the east side of the upper trough...the rain is heaviest...which is in the northern quadrants of Hermine's circulation and currently over eastern North Carolina and southeastern Virginia. As of 0000Z this evening the center of Hermine was moving northeastward near the Carolina coast at 33.5N-79.5W.

Atmospheric Outlook for the Forecast Period...The upper trough and surface 1007 mb frontal cyclone moving into the Atlantic from the northeastern United States has been steering Hermine northeastward across the southeastern United States...but soon is about to outrun and leave behind Hermine while the 1029 mb ridge from the Great Lakes supported by convergence on the west side of the upper trough takes over the steering. However Hermine fairly soon will transition into a non-tropical remnant gale along the cold front of the frontal cyclone supported by divergence on the east side of the upper trough as it moves into the Atlantic offshore of the US mid-Atlantic coast. During the transition the 1029 mb ridge will block Hermine's remnant from continuing northeastward...and the west side of the remnant gale will pull cooler air associated with the tail end of the upper trough southward which in turn will cause the upper trough tail to amplify into a cut-off upper vortex. Intensifying upper air divergence on the east side of the amplifying cut-off will cause the remnant of Hermine to significantly intensify while intensifying convergence on the west side of the cut-off causes another surface ridge to form west of Hermine. Thus the intensifying remnant of Hermine is expected to be trapped stationary offshore of the US mid-Atlantic coast in between the western ridge and 1029 mb ridge as it moves to Hermine's northeast. Hermine's remnant could be stuck offshore of the mid-Atlantic US for as much as one week until a frontal cyclone strong enough to whisk it away from shore captures it. As the remnant of Hermine becomes vertically stacked with the forecast cut-off upper vortex...the south side of its circulation will be over 26 deg C waters which combined with the cold temps of the upper vortex may allow enough instability for the remnant to re-develop thunderstorms over the center and transition into a subtropical storm. However waiting to see the state of Hermine after it becomes stacked with the upper vortex before issuing any forecast for a subtropical storm Hermine...and thus my forecast only goes out the next 24 hours as Hermine is expected to become non-tropical soon.

Thermodynamic Outlook for the Forecast Period...As Hermine stalls offshore of the US mid-Atlantic coast over the next week...its south half will be over 26 deg C waters which may help this system transition into a subtropical storm per the end of the above atmospheric outlook section.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 4)...Vigorous remnant frontal low centered offshore of the mid-Atlantic US coast at 36.5N-73.5w

Track Forecast...Based on the 0000Z center fix in the above current prognosis Hermine is east of my previous track forecast and therefore my updated forecast track is adjusted eastward accordingly.

Intensity Forecast...Hermine is maintaining strength and in fact will get stronger as it transitions to non-tropical while stalling offshore of the US mid-Atlantic coast. See above current prognosis and atmospheric outlook sections for more details on why.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along the forecast track. In addition to some wind damage from tropical storm winds...heavy rain with flash flooding potential is possible for the remainder of the evening for eastern North Carolina and southeastern Virginia based on the lastest radar presentation. A period of storm surge and sea swells along the mid-Atlantic and northeastern US is expected as the remnant of Hermine intensifies offshore. Its possible some western outer rain bands with gusty winds may reach the mid-Atlantic and northeastern US coastal regions over the next few days if the remnant of Hermine wobbles close enough to land.

...SPECIAL FEATURE...TROPICAL STORM GASTON...
Current Prognosis...While moving into the Azores islands...Gaston has lost all thunderstorm activity due to some suppressing upper convergence on the northeast side of an upper ridge that is beginning to overspread Gaston. This has resulted in Gaston rapidly weakening from a category 1 hurricane to a minimal 40 mph maximum sustained wind tropical storm in the last 24 hours. Because Gaston is over cool waters...its remnant swirl is not likely to re-generate thunderstorms and thus dissipation into a remnant low is possible at any time. As of 0000Z this evening the center of Gaston was in the midst of the Azores islands at 39.6N-29.8W.

Atmospheric Outlook for the Forecast Period...The remnant of Gaston will likely turn northeastward away from the Azores in the next 24 hours while getting caught in southwesterly flow on the east side of the 1007 mb frontal cyclone emerging into the north Atlantic from the northeastern US. The remnant will lose its identity within the low pressure field of this frontal cyclone as the frontal cyclone intensifies.

Thermodynamic Outlook for the Forecast Period...Gaston has crossed the 26 deg C isotherm into cooler waters and thus weakening is expected for the remainder of Gaston's life.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 4)...Remnant low centered at 43.5N-25.5W

Track Forecast...Gaston is essentially along my previous forecast track per the 0000Z fix in the above current prognosis...and therefore I am making no changes.

Intensity Forecast...Gaston will dissipate into a remnant low at any time per the above current prognosis.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track.

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 92-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...Tropical wave Invest 92-L in the central tropical Atlantic has seen an increase in the intensity and organization of its thunderstorms due to favorable upper-level dynamics. Specifically the east side of the inverted upper trough to the west is enhancing the poleward upper outflow...and a small upper anticyclone is forming over the tropical wave in relatively higher pressures to the southeast of the inverted upper trough. This small upper anticyclone is also enhancing the upper outflow in all directions and keeping the vertical shear over the tropical wave favorably low for tropical development. Based on the organization of the thunderstorms and satellite animation...the tropical wave has a low pressure spin which passed over 13.5N-47W as of 0000Z earlier this evening.

Atmospheric Outlook for the Forecast Period...Because the inverted upper trough mentioned in the above current prognosis will continue to retrograde westward...the favorable upper air pattern mentioned in the above current prognosis is expected to continue with the favorable upper anticyclone growing over the tropical wave while the less favorable inverted upper trough diminishes. There is a possiblity though this tropical wave will run into the east side of the inverted upper trough at 72 hours which will cause some light southerly vertical shear. Thus in the forecast listed below I slow the development of this system around 72 hours. However by the end of the forecast period...this system should slow its westward pace and begin bending northward in track in response to a ridge weakness caused by the remnant of Hermine and its upper trough...which will increase the distance betweeen this system and still-retrograding inverted upper trough...resulting in a reduction in shear over this system. Thus the development rate is increased again at the end of the forecast period (96 to 120 hours).

Thermodynamic Outlook for the Forecast Period...This system will enter rather favorable 30 deg C waters across the Caribbean Sea by the end of the forecast period. Therefore if atmospheric conditions become favorable per the above atmospheric outlook section...this system could signficantly strengthen. The favorable upper atmospheric pattern mentioned in the above current prognosis has cuased this tropical wave to develop thunderstorms and mix out the dry air that was plaguing it...and with this pattern expected to continue dry air is not expected to be an issue for this system going forward.

24 Hr Forecast (0000Z Sep 4)...Tropical low approaching the Lesser Antilles centered at 14N-55W

48 Hr Forecast (0000Z Sep 5)...Tropical low just below tropical depression strength in the eastern Caribbean Sea...centered at 14.5N-63W

72 Hr Forecast (0000Z Sep 6)...35 mph maximum sustained wind tropical depression under light southerly shear just south of Haiti and the Dominican Republic centered at 16.5N-69W

96 Hr Forecast (0000Z Sep 7)...50 mph maximum sustained wind tropical storm centered between Haiti and Jamaica at 18N-75W

120 Hr Forecast (0000Z Sep 8)...75 mph maximum sustained wind hurricane centered over the Cayman Islands at 20N-80.5W

2016 Atlantic Hurricane Season Birdseye Discussion #105

By: NCHurricane2009, 3:09 AM GMT on September 02, 2016

...THURSDAY SEPTEMBER 1 2016 11:09 PM EDT...
Alert! There are multiple active tropical cyclones and areas of disturbed weather with effects to multiple land areas expected over the next few days. Please read all statements below for a full comprehension...

Hermine continues to briskly strengthen and is now a category 1 hurricane. Weather conditions are detereorating in northern Florida and southern Georgia as Hermine is approaching landfall. Vigorous weather is also expected in the eastern parts of the Carolinas...and the remnants of Hermine are expected to retain gale force winds which will cause sea swells along the mid-Atlantic and northeastern US coast over the next few days. See first special feature section below for additional details on Hermine. Visit www.nhc.noaa.gov for up to the minute latest information on Hermine.

Hurricane Gaston in the northeastern Atlantic Ocean continues weakening while encountering westerly vertical shear and cooler water temperatuers...and is expected to arrive in the Azores and bring tropical storm conditions within the next 24 hours. See second special feature section below for additional details on Gaston. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston.

In addition to our two active tropical cyclones...there are two other areas of interest...see the following statements...

The following statement concerns area of interest #1 marked over the centraltropical Atlantic in the atmospheric features chart below. The vigorous tropical wave in this region continues to be suppressed by dry saharan air in the central tropical Atlantic...and will later catch up to the less favorable inverted upper trough to its west as both the tropical wave and inverted upper trough arrive into the eastern Caribbean together. Therefore chances for tropical cyclone formation from this tropical wave remain low. However enhanced poleward upper outflow provided by the east side of the inverted upper trough may help to re-invgorate the tropical wave and therefore some vigorous weather (heavy rain with gusty winds) may occur over the northern Lesser Antilles and northern Caribbean Sea islands in the next few days.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. Satellite imagery shows another vigorous and somewhat organized tropical wave has emerged from Africa...but the low pressure spin was north enough such that it ingested some dry air from the saharan desert to the north and therefore its thunderstorm activity has weakened. Subsequently it is also likely to become suppressed further by the mass of saharan air in the central tropical Atlantic. Therefore tropical cyclone formation is not likely from this tropical wave over the next few days. Meanwhile in the short-term...islands of the Republic of Cabo Verde may experience some gusty winds and heavy rain from this tropical wave over the next day or so.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1922Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...HURRICANE HERMINE...
Current Prognosis...This past afternoon...the mass of thunderstorms over and east of the center progressively wrapped completely around the center while developing a large and broad eye...with the eye becoming much tighter and clearer during sunset. Thus Hermine is now a category 1 hurricane with 80 mph maximum sustained winds as of 8 PM EDT...and with the aforementioned tightening and clearing eye this maybe a sign some additional strengthening may be going on before Hermine makes landfall on the Florida panhandle coast late tonight. As of 0000Z this evening the eye of Hermine was located at 29.1N-84.8W.

Atmospheric Outlook for the Forecast Period...The upper trough and surface 1009 mb frontal cyclone currently over the northeastern United States has amplified...which is causing Hermine to accelerate northeastward toward north Florida and southeastern United States while steered by this system. After landfall in north Florida...Hermine is expected to transition into a non-tropical remnant frontal gale when the cold front of the 1009 mb frontal cyclone overspreads Hermine. The remnant will retain some strength a few days after the landfall while becoming supported by upper divergence on the east side of the upper trough associated with the front.

Thermodynamic Outlook for the Forecast Period...Water temps of 30 deg C in the northeastern Gulf of Mexico will support the potential for additional strengthening in the next few hours before Hermine makes landfall.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 3)...Vigorous remnant frontal low centered over west-central South Carolina at 33N-81.5W

Track Forecast...Based on the 0000Z center fix in the above current prognosis Hermine is a bit north of my previous track forecast and therefore my updated forecast track is adjusted accordingly.

Intensity Forecast...After landfall in north Florida...Hermine will transition to a non-tropical remnant frontal gale still packing tropical storm force winds when the cold front of the 1009 mb frontal cyclone over the northeastern US overspreads Hermine. The remnant of Hermine will retain tropical storm force winds for a period of time due to supportive upper divergence on the east side of the upper trough associated with the front and thus impacts may linger for a few more days along the mid-Atlantic and northeast US coast after the transition to non-tropical.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 5 PM EDT NHC tropical storm wind radius along the forecast track. In addition to wind damage from tropical storm and hurricane force winds...this system is expected to bring heavy rain with flash flooding risk across Florida and parts of the southeastern United States. The National Weather Service has raised tornado watches in northeast Florida and mentions the threat of tornadoes in the areas over the southeastern United States to be affected by Hermine. This is because the low-level southeasterly flow on Hermine's east side will be in vertical shear with respect to strong upper-level southwesterly flow on the east side of the aforementioned upper trough...and this shear supports tornado potential. Therefore I have added a tornado statement in the above forecast graphic.

...SPECIAL FEATURE...HURRICANE GASTON...
Current Prognosis...Gaston has lost its large eye and has weakened further due to the effects of westerly vertical shear and cooler water temperatures. As of 8 PM EDT (0000Z) Gaston was a category 1 hurricane with 80 mph maximum sustained winds and was centered at 38.3N-37.3W

Atmospheric Outlook for the Forecast Period...Gaston continues to move rapidly eastward due to deep-layered westerly flow being supplied by the 989 mb frontal cyclone and upper trough passing by the hurricane to its immediate north. The hurricane remains embedded beneath high-latitude linear (zonal) upper westerlies on the north side of the central Atlantic upper anticyclonic flow which is inducing the unfavorable westerly shear noted in the above current prognosis. However the weakening in the shear is not rapid as Gaston's cyclonic circulation has pulled down some of the cold air associated with the upper trough to the north...which has caused a small upper trough to form just west of Gaston...and in turn upper divergence on the east side of this upper trough is helping Gaston. The next 24 to 48 hours will be dominated by interaction with what is now the northeastern US 1009 mb frontal cyclone. Low-level southerly flow ahead of this frontal cyclone will cause warm air advection and hence deep-layered ridging to build across the north Atlantic over and to the west of Gaston...with this ridging helping to bend the track more eastward by 24 hours while also reducing the shear. By 48 hours as the frontal cyclone nears...it should scoop Gaston more northeastward into the cold northeast Atlantic waters where Gaston should lose thunderstorms and hence its tropical characteristics despite remaining in a low shear environment.

Thermodynamic Outlook for the Forecast Period...Gaston has crossed the 26 deg C isotherm into cooler waters and thus weakening is expected for the remainder of Gaston's life.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0000Z Sep 3)...60 mph maximum sustained wind tropical storm centered just north of the Azores at 39.5N-30.5W

48 Hr Forecast (0000Z Sep 4)...30 mph maximum sustained wind remnant low centered at 43.5N-25.5W

Track Forecast...Gaston is a little west of my previous track forecast and therefore I have adjusted my forecast track accordingly.

Intensity Forecast...Because Gaston is still a hurricane I have slightly raised the intensity forecast. Even though Gaston will be moving into cooler waters not supportive of a tropical cyclone for the rest of the forecast period...rapid dissipation is not shown due to current supportive upper divergence from a local upper trough...followed by a reduction in shear expected at 24 to 48 hours...per the above atmospheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 5 PM EDT NHC tropical storm wind radius along my forecast track. Interests in the Azores should have finished preparations for tropical storm conditions as Gaston will march in during the next 24 hours. A tropical storm warning is currently in effect for parts of the Azores.

2016 Atlantic Hurricane Season Birdseye Discussion #104

By: NCHurricane2009, 12:25 PM GMT on September 01, 2016

...THURSDAY SEPTEMBER 1 2016 8:30 AM EDT...
Alert! There are multiple active tropical cyclones and areas of disturbed weather with effects to multiple land areas expected over the next few days. Please read all statements below for a full comprehension...

Tropical depression nine rapidly strengthens to strong Tropical Storm Hermine in the eastern Gulf of Mexico and could become a hurricane later today before making landfall in the Florida panhandle early tomorrow morning. Preparations for Hermine in the warned areas of Florida and southern Georgia should be completed this afternoon before weather conditions detereorate tonight. Vigorous weather will also be possible in the eastern parts of the Carolinas toward the coast...and the remnants of Hermine are expected to retain gale force winds which will cause sea swells along the mid-Atlantic and northeastern US coast over the next few days. See second special feature section below for additional details on Hermine. Visit www.nhc.noaa.gov for up to the minute latest information on Hermine.

Hurricane Gaston in the central Atlantic Ocean weakens while encountering westerly vertical shear and cooler water temperatuers...and is expected to arrive in the Azores and bring tropical storm conditions in the 24 to 36 hours. Interests in the Azores should finish preparing for tropical storm conditions today. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston.

In addition to our two active tropical cyclones...there are three other areas of interest...see the following statements...

The following statement concerns area of interest #1 marked in the atmospheric features chart below. Tropical depression eight dissipates into a sheared remnant low offshore of the mid-Atlantic coast of the United States and should soon lose its identity as the cold front from the 1007 mb frontal cyclone over the northeastern US and eastern Canada moves offshore and absorbs it. This is my final statement on this blog regarding tropical depression eight.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. The vigorous tropical wave in this region has not regained thunderstorm activity before entering the dry saharan air in the central tropical Atlantic...and because it is moving faster to the west it is now expected to catch up to the less favorable inverted upper trough currently in the central Atlantic as both the tropical wave and inverted upper trough arrive into the eastern Caribbean together. Therefore I have cancelled it as a special feature on this blog as tropical cyclone formation has become less likely. However enhanced poleward upper outflow provided by the east side of the inverted upper trough may help to re-invgorate the tropical wave and therefore some vigorous weather (heavy rain with gusty winds) may occur over the northern Lesser Antilles and northern Caribbean Sea islands in the next few days.

The following statement concerns area of interest #3 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Satellite imagery shows another vigorous and somewhat organized tropical wave has become better organized with a tropical low pressure spin about to emerge into the eastern tropical Atlantic. However like tropical wave Invest 92-L to its west (area of interest #2 discussed above)...the low pressure spin is emerging at a northern latitude closer to the saharan desert and thus may ingest some dry saharan air and then become suppressed further by the mass of saharan air in the central tropcial Atlantic. Therefore I have not yet upgraded this tropical wave to a special feature with a tropical cyclone formation forecast while waiting to see if this tropical wave retains organization while moving into the Atlantic. However the islands of the Republic of Cabo Verde may experience some gusty winds and heavy rain from this tropical wave over the next day or so.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0128Z-released WPC analysis.

Areas of Interest maybe first introduced circled by a yellow-dashed line. If the area of interest becomes introduced in the 5-day National Hurricane Center (NHC) Atlantic tropical weather outlook then it gets upgraded with a green-dashed line encircling it. If the area of interest gets upgraded to an Invest or is mentioned in the 48-hour NHC Atlantic tropical weather outlook then it gets upgraded with a green-solid polygon encircling it.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows (also called an upper vortex or upper cyclone), blue Hs are locations of upper ridges (also called upper anticyclones).

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Surface troughs labeled with TW indicates the trough is a tropical wave whose origin is from the mid-level African Easterly Jet. Ls indicate surface lows (cyclones), Hs indicate surface highs (ridges/anticyclones).

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM HERMINE...
Current Prognosis...Finally the surface and mid-level centers of tropical depression nine have become stacked...and combined with the supportive outflow of the upper-level anticyclone in the eastern Gulf of Mexico and warm 30 to 31 deg C water temperatures tropical depression nine has rapidly strengthened to a strong Tropical Storm Hermine in the last 24 hours. As of the 5 AM EDT National Hurricane Center Advisory Hermine had maximum sustained winds of 60 mph...with the latest satellite appearance suggesting further strengthening to a category 1 hurricane may be possible later today as the mass of thunderstorms over and east of the center both grows in size and intensity. As of 0600Z this morning the surface center of Hermine was located at 26N-87W.

Atmospheric Outlook for the Forecast Period...The upper trough and surface 1007 mb frontal cyclone currently over eastern Canada and northeastern United States has amplified...which is causing Hermine to accelerate northeastward toward north Florida and southeastern United States while steered by this system. Just before landfall in northern Florida...conditions will become less favorable for tropical development while the tropical cyclone encounters westerly shear on the north side of the upper anticyclone mentioned in the above current prognosis and on the south side of the aforementioned upper trough.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C before landfall and thus thermodynamic conditions are supportive for some additional strengthening.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0600Z Sep 2)...75 mph maximum sustained wind hurricane making landfall on the Florida panhandle at 29N-84.5W

48 Hr Forecast (0600Z Sep 3)...Vigorous remnant frontal low centered over northeastern South Carolina at 33N-80W

Track Forecast...Hermine's surface center did not relocate quiet as far to the east as I previously forecasted and therefore is 2W longitude west of my previous forecast. Therefore I have shifted my forecast track 2W westward.

Intensity Forecast...Although Hermine is on par with my previous intensity forecast...I have raised the intensity forecast and I am in agreement with the latest National Hurricane Center (NHC) forecast which shows Hermine as a minimal category 1 hurricane at landfall in the Florida panhandle. This is because the westward adjusted track gives it a little more time over water before landfall...and because the storm structure is becoming impressive per the above current prognosis section. There is some possiblity that increased shear just before landfall (per the above atmospheric outlook section) may prevent strengthening into a hurricane or may cause Hermine to weaken back to a tropical storm...but I would rather err on the side of caution and show a hurricane at landfall rather than risking under-predicting the landfall intensity. On a final note...Hermine will transition to a non-tropical remnant frontal gale still packing tropical storm force winds when the cold front of the 1007 mb frontal cyclone over eastern Canada and northeastern US overspreads Hermine. The remnant of Hermine will retain tropical storm force winds for a period of time due to supportive upper divergence on the east side of the upper trough associated with the front and thus impacts may linger along the mid-Atlantic and northeast US coast after the transition to non-tropical.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 5 AM EDT NHC tropical storm wind radius along the forecast track. In addition to possible wind damage from tropical storm or hurricane force winds...this system is expected to bring heavy rain with flash flooding risk across Florida and parts of the southeastern United States.

...SPECIAL FEATURE...HURRICANE GASTON...
Current Prognosis...Gaston continues to have an annular appearance with a large eye and solid single thick ring of thunderstorms around the eye...but the thunderstorms have weakened and the hurricane looks more distorted due to the effects of westerly vertical shear. Therefore Gaston is no longer a major (category 3+) hurricane and is instead has weakened to a category 1 with 90 mph maximum sustained winds. As of 0600Z this morning the center of the large eye was at 36.5N-44W.

Atmospheric Outlook for the Forecast Period...Gaston continues to move rapidly eastward due to deep-layered westerly flow being supplied by the 988 mb frontal cyclone and upper trough passing by the hurricane to its immediate north. The hurricane remains embedded beneath high-latitude linear (zonal) upper westerlies on the north side of the central Atlantic upper anticyclonic flow which is inducing the unfavorable westerly shear noted in the above current prognosis. In the next 24 hours Gaston's cyclonic circulation will pull down some of the cold air associated with the upper trough to the north...which will cause a small upper trough to form just west of Gaston...and in turn upper divergence on the east side of this upper trough may help Gaston maintain some strength while moving into cooler northeastern Atlantic waters. The 48 to 72 hour timeframe will then be dominated by interaction with what is now the eastern Canada 1007 mb frontal cyclone. Low-level southerly flow ahead of this frontal cyclone will cause warm air advection and hence deep-layered ridging to build across the north Atlantic over and to the west of Gaston...with this ridging helping to bend the track more eastward by 48 hours while also reducing the shear. By 72 hours as the frontal cyclone nears...it should scoop Gaston more northeastward into the cold northeast Atlantic waters where Gaston should lose thunderstorms and hence its tropical characteristics despite remaining in a low shear environment.

Thermodynamic Outlook for the Forecast Period...Gaston has crossed the 26 deg C isotherm into cooler waters and thus weakening is expected for the remainder of Gaston's life.


My (red) track and intensity forecast points in the above graphic:

24 Hr Forecast (0600Z Sep 2)...70 mph maximum sustained wind tropical storm centered just west of the Azores at 39N-34W

48 Hr Forecast (0600Z Sep 3)...50 mph maximum sustained wind tropical storm centered just north of the Azores at 39.5N-28W

72 Hr Forecast (0600Z Sep 4)...Remnant low centered at 45N-24W

Track Forecast...Gaston is a little north and west of my previous track forecast. However the latest model runs suggest Gaston will catch up and still align with the eastward positions of my previous forecast. And despite being slightly north of my previous forecast...I have adjusted my forecast track a little southward to be more in agreement with the latest NHC forecast and computer model runs.

Intensity Forecast...I have lowered the intensity forecast due to Gaston already weakening to a category 1 hurricane. Even though Gaston will be moving into cooler waters not supportive of a tropical cyclone for the rest of the forecast period...I do not show rapid dissipation of Gaston due to some supportive upper divergence expected from a local upper trough expected in the next 24 hours...followed by a reduction in shear at 48 to 72 hours...per the above atmospheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 5 AM EDT NHC tropical storm wind radius along my forecast track. Interests in the Azores should finish preperations for tropical storm conditions from Gaston. A tropical storm warning is currently in effect for parts of the Azores.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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