NCHurricane2009's Blog

2016 Atlantic Hurricane Season Birdseye Discussion #103

By: NCHurricane2009, 10:04 AM GMT on August 31, 2016

...WEDNESDAY AUGUST 31 2016 6:05 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 continues to become better organized in the southeastern Gulf of Mexico. Therefore a tropical storm is expected to develop in the eastern Gulf of Mexico at any time. Tropical storm warnings are in effect for parts of northern Florida and strong weather will also be possible over southern Georgia and southern South Carolina. See second special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression nine.

Tropical depression eight is now turning away from the North Carolina Outer Banks and thus the threat to land is over. The tropical depression will become absorbed by a cold front moving offshore from the United States over the next day or so. See first special feature below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression eight.

Gaston in the central Atlantic Ocean regains category 3 major hurricane status...and is expected to curve eastward toward the Azores islands in the northeast Atlantic over the next 2 to 3 days. Interests in the Azores should prepare for tropical storm conditions...and hurricane conditions may reach the westernmost Azores. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston.

In addition to our three 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 western Gulf of Mexico...southern Texas...and northeastern Mexico in the atmospheric features chart below. The upper vortex and surface low pressure center of the disturbance in this region has dissipated...with an upper ridge in the wake of the upper vortex supporting the remainder of the thunderstorm activity by supplying upper outflow. What's left of this disturbance is expected to dissipate over southern Texas and northeastern Mexico. This is my final statement on this blog concerning this disturbance.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic and Republic of Cabo Verde in the atmospheric features chart below. Although the vigorous tropical wave in this region has lost thunderstorm activity while emerging from Africa...conditions are generally favorable for the tropical wave to re-organize while it moves across the Atlantic tropics. Interests in the Lesser Antilles and northern Caribbean Sea islands should watch the progress of this tropical wave over the next few days. See fourth special feature section below for additional details.

The following statement concerns area of interest #3 marked over Africa in the atmospheric features chart below. Satellite imagery shows another vigorous and somewhat organized tropical wave is moving across southern Mali in western Africa. Although current computer model support is weak...conditions in the tropical Atlantic will also be generally favorable for this tropical wave as it emerges from Africa and therefore this tropical wave should also be watched over the next few days. If it remains organized as it enters the tropical Atlantic I will consider upgrading it to a special feature with a tropical cyclone formation forecast on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0431Z-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 EIGHT...
Current Prognosis...Although tropical depression eight has been able to fire some showers and thunderstorms over the center...the activity has not been persistent enough to strengthen it to a tropical storm. As of 0600Z this morning the center of tropical depression eight was just east of Cape Hatteras North Carolina at 35N-74.5W. However none of the thunderstorm activity is affecting land as the activity is becoming displaced eastward from the center under some developing westerly vertical shear.

Atmospheric Outlook for the Forecast Period...For the remainder of the forecast period tropical depression eight will be under westerly vertical shear beneath a jet that extends across the northwestern Atlantic upper trough to the northeast of the depression and upper trough associated with the eastern Canada frontal cyclone to the northwest of the depression. In the next 24 hours...tropical depression eight is expected to rapidly accelerate northeast while becoming scooped up by the frontal cyclone incoming from eastern Canada...and not long after that time become absorbed by the cold front of the frontal cylcone.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 29 to 30 deg C waters during the forecast period.


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

24 Hr Forecast (0600Z Sep 1)...35 mph maximum sustained wind tropical storm centered offshore of the mid-Atlantic United States at 37.5N-73W becoming absorbed by a cold front

Track Forecast...Tropical depression eight is slighlty south of my previous track forecast and so I have slightly adjusted my updated track forecast southward accordingly.

Intensity Forecast...Tropical depression eight is running out of time to become a tropical storm as less favorable westerly vertical shear will be increasing for the remainder of its lifespan. It remains to be seen if the latest thunderstorm burst mentioned in the above current prognosis can strengthen it to a minimal tropical storm later this morning. If not...then do not expect this system to become a tropical storm.

Impact Forecast...No significant impacts are expected for the remainder of the forecast period as this system only has about a day left to be a tropical cyclone...and at most it will be a minimal small-sized tropical storm.

...SPECIAL FEATURE...TROPICAL DEPRESSION NINE...
Current Prognosis...Despite the satellite appearance of the tropical depression becoming impressive across the southeastern Gulf of Mexico over the last 24 hours...latest observations from ships and aircraft reconaissance indicate the troipcal depression still has not strengthened. It appears then most of the organization has occurred around a mid-level center that is further southeast while the surface center remains weak. As of 0600Z this morning the surface center was at 24.3N-88.1W.

Atmospheric Outlook for the Forecast Period...The upper trough and surface frontal cyclone currently over eastern Canada are expected to both rapidly amplify while moving onto the east coast of the United States...and therefore this tropical depression is expected to accelerate northeastward toward north Florida and southeastern United States while steered by this system. Given that the surface center has not yet turned northward and instead and has been moving erratically...this may be a sign the surface center is trying to re-generate southeastward toward the highly-organized mid-level center and upper anticyclone where surface pressure falls are likely to be maximized due to the outflow of the upper anticyclone. Thus my latest forecast assumes some south or eastward regeneration of the surface center will occur before the surface center will accelerate northeastward. Towards the end of the forecast period...just before landfall...conditions will become less favorable for tropical development while the tropical cyclone encounters westerly shear on the north side of the upper anticyclone and south side of the upper trough.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C waters during the forecast period. Thus significant strengthening is possible during the next 24 hours if the structure of the troipcal cyclone improves (specifically if the surface and mid-level centers become vertically aligned per the above atmospheric outlook section).


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

24 Hr Forecast (0600Z Sep 1)...60 mph maximum sustained wind tropical storm centered in the northeastern Gulf of Mexico at 26N-85W

48 Hr Forecast (0600Z Sep 2)...45 mph maximum sustained wind tropical storm centered over northeastern Florida at 29N-82.5W

72 Hr Forecast (0600Z Sep 3)...Vigorous remnant frontal low centered just offshore of the Carolinas at 33N-78W

Track Forecast...I have adjusted my track forecast both south and east with the assumption that the surface center re-generates toward the more organized upper-level structure of the storm per the above atmospheric outlook section.

Intensity Forecast...I have lowered the overall intensity forecast as this system has not yet been able to strengthen to a tropical storm. However I have not lowered the intensity forecast for the end of the forecast period as this system becomes non-tropical...as it appears this system will align with supportive upper divergence on the east side of the upper trough associated with the frontal cyclone that will come from central Canada.

Impact Forecast...Impact swath in the above forecast graphic assumes the development of a sizeable area of tropical storm force winds at the center per the intensity forecast. In addition to possible wind damage from tropical storm 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...MAJOR HURRICANE GASTON...
Current Prognosis...After emerging from an eye wall replacement with a larger eye...Gaston has re-intensified into a major category 3 hurricane with 120 mph maximum sustained winds. Gaston's satellite apperance basically looks like an impressive "truck tire" or "donut"...or in more technical terms looks annular in that the outer spiral thunderstorm bands have consolidated into a single thick ring of thunderstorms around the large eye. As of 0600Z this morning the center of the large eye was at 33.1N-50.5W

Atmospheric Outlook for the Forecast Period...Gaston continues to accelerate eastward due to deep-layered westerly flow being supplied by the intensifying 986 mb frontal cyclone and upper trough passing by the hurricane to its immediate north. Upper-level winds are expected to prevent additional strengthening as Gaston is now embedded in high-latitude linear (zonal) upper westerlies on the north side of the central Atlantic upper anticyclonic flow which is inducing some shear. The latest model runs suggest Gaston's cyclonic circulation will be able to 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 by 48 hours. Also by 48 hours...the 1027 mb ridge in the northeast Atlantic may be strong enough to bend Gaston more northward in track. The 72 to 96 hour timeframe will then be dominated by interaction with what is now the eastern Canada 1010 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 72 hours while also reducing the shear. By 96 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...Water temps will be supportive for Gaston until 36 hours and beyond...when Gaston crosses the 26 deg C isotherm and ventures into and across cooler waters in the northeast Atlantic.


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

24 Hr Forecast (0600Z Sep 1)...110 mph maximum sustained wind hurricane centered at 35.5N-42.5W

48 Hr Forecast (0600Z Sep 2)...90 mph maximum sustaiend wind hurricane centered just west of the Azores at 40N-34W

72 Hr Forecast (0600Z Sep 3)...60 mph maximum sustained wind tropical storm centered just north of the Azores at 41N-28W

96 Hr Forecast (0600Z Sep 4)...40 mph maximum sustained wind tropical storm with dissipating thunderstorms and transitioning into a remnant low...centered at 46N-24W

Track Forecast...Gaston remains on track with the previous forecast and therefore I have made no changes to my track forecast.

Intensity Forecast...Gaston has been able to strengthen after completion of its eye wall replacement cycle despite the increase in less favorable westerly vertical shear...and thus I have upped the first part of the intensity forecast. Even though Gaston will be moving into cooler waters not supportive of a tropical cyclone for much of the forecast... I do not show rapid dissipation of Gaston due to some supportive upper divergence expected from a local upper trough at 48 hours...followed by a reduction in shear at 72 to 96 hours...per the above atmospheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track. Interests in the Azores should monitor the progress of Gaston and prepare for tropical storm conditions arriving in 48 to 72 hours. Hurricane conditions may reach the westernmost Azores.

...SPECIAL FEATURE...EASTERN ATLANTIC 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 has seen a significant decrease in its thunderstorm activity. Perhaps this was due to ingestion of dry Saharan air as the tropical wave did come off of Africa at a higher latitude toward the Saharan desert to the north...but not entirely sure about this theory as water vapor imagery shows that the tropical wave is still embedded in a moist air mass. As of 0600Z the cloudiness on satellite imagery suggested the low pressure spin of the tropical wave was centered over the Republic of Cabo Verde at 14N-23.5W...which is in alignment with my previous track forecast and therefore I have made no changes to the track forecast listed below.

Atmospheric Outlook for the Forecast Period...The 1019 mb ridge center currently moving into the Atlantic from the northeastern US...and 1027 mb ridge in the northeast Atlantic are merging...with the combined ridge expected to steer this system westward during the forecast period. Upper-level winds are expected to be favorable during the forecast period...with this system expected to move across a vast area of upper anticyclonic flow in the tropics that will provide low shear and good upper outflow. However given the degraded satellite apperance of the tropical wave in the above current prognosis...I have now delayed forecast tropical cyclone formation till 0600Z September 3. Another thing to watch for is the cut-off inverted upper trough in the central Atlantic which is expected to retrograde westward and away within the upper anticyclonic flow...and so far computer models show this trough staying to the west of this system during the forecast period. However if this trough does not retrograde westward as fast in later model runs...conditions later in the forecast period may not be as favorable for tropical development.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 29 deg C waters during the forecast period. Even though latest water vapor satellite imagery suggests this system is well-embedded in a moisture field...dry saharan air may be an issue for this system as noted in the above current prognosis. The dry saharan air is much more defined in the central tropical Atlantic in the latest water vapor imagery...and so if this system does not re-develop thunderstorm activity before reaching the cnetral Atlantic it may struggle to develop even more than shown in the forecast listed below.

24 Hr Forecast (0600Z Sep 1)...Tropical low centered at 14.2N-30W

48 Hr Forecast (0600Z Sep 2)...Tropical low centered at 15.2N-38W

72 Hr Forecast (0600Z Sep 3)...35 mph maximum sustained wind tropical depression centered at 16.2N-46W

96 Hr Forecast (0600Z Sep 4)...45 mph maximum sustained wind tropical storm centered at 17.2N-54W

120 Hr Forecast (0600Z Sep 5)...60 mph maximum sustained wind tropical storm over the northern Lesser Antilles and Virgin Islands...centered at 17.5N-62W

2016 Atlantic Hurricane Season Birdseye Discussion #102

By: NCHurricane2009, 4:20 AM GMT on August 30, 2016

...TUESDAY AUGUST 30 2016 12:30 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 is slowly becoming better organized while entering the southeastern Gulf of Mexico. Therefore a tropical storm is expected to develop in the eastern Gulf of Mexico over the next couple of days...and development into a category 1 hurricane cannot be ruled out. Interests in the Gulf of Mexico and southeastern United States regions inland from the Gulf coast should carefully monitor the progress of this tropical depression. See second special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression nine.

Tropical depression eight continues to approach the North Carolina Outer Banks where tropical storm warnings have been posted. Heavy rainfall is possible in parts of eastern North Carolina and the Outer Banks...with gusty winds possible in the Outer Banks...in the next 24 hours. See first special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression eight.

Gaston in the central Atlantic Ocean weakens back to a category 2 hurricane due to an eye wall replacment cycle...and is expected to curve eastward toward the Azores islands in the northeast Atlantic over the next 3 to 4 days where tropical storm conditions are possible. Interests in the Azores should monitor the progress of Gaston and perhaps begin thinking about preparations. See third special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston.

In addition to our three 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 northwestern Gulf of Mexico...Louisiana...and southeastern Texas in the atmospheric features chart below. The National Hurricane Center 48-hour tropical weather outlook continues to note the area of disturbed weather currently supported by a decaying upper vortex in this region. The temperatures of the upper vortex are not cold enough to de-stabilize the atmosphere near the surface low pressure center of this disturbance and thus is only acting to suppress this surface low from developing. Instead most of the activity is to the northeast of the surface low over eastern Texas and Louisiana while supported by upper outflow of a small upper anticyclone developing over Louisiana in the wake of the decaying upper vortex. Tropical cyclone formation here is not expected.

The following statement concerns area of interest #2 marked over Africa in the atmospheric features chart below. The tropical wave that was moving over western Africa has quickly strengthened and organized while nearing the eastern tropical Atlantic...and is now designated as tropical disturbance Invest 92-L. Conditions are quiet favorable for this tropical wave to strengthen into a significant tropical cyclone while it moves across the Atlantic tropics and thus interests in the Lesser Antilles and northern Caribbean Sea islands should watch the progress of this tropical wave over the next several days. In the short-term...expect vigoruos weather (heavy rain with gusty winds) to overspread the islands of the Republic of Cabo Verde in the next 24 to 36 hours. See fourth 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 1923Z-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 EIGHT...
Current Prognosis...Compared to last evening tropical depression eight looks better with some showers and thunderstorms firing and covering the swirl center...but at times this activity is weak and thus this system is still not a tropical storm. As of 0000Z this evening the center of the tropical depression passed over 33.6N-74W.

Atmospheric Outlook for the Forecast Period...The easterly and southerly vertical shear that was being imparted by the upper vortex to the immediate southwest is beginning to switch to westerly as the base of the upper trough currently over the northeastern US has neared the tropical cyclone...and the westerly shear will be continued through the end of the forecast period as the upper trough associated with the central Canada frontal cyclone follows behind. The steering low-level ridge that was north of the tropical cyclone has weakened due to the 1001 mb frontal cyclone associated with the upper trough over the northeastern US which has resulted in tropical depression eight slowing down as it approaches Cape Hatteras North Carolina. By 48 hours...the frontal cyclone from central Canada should drive this tropical cyclone northeast and absorb it with its cold front.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 29 to 30 deg C waters during the forecast period.


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

24 Hr Forecast (0000Z Aug 31)...45 mph maximum sustained wind tropical storm centered just east of Cape Hatteras North Carolina at 35.2N-75W

48 Hr Forecast (0000Z Sep 1)...35 mph maximum sustained wind tropical storm centered offshore of the mid-Atlantic United States at 37.7N-73.5W becoming absorbed by a cold front

Track Forecast...Tropical depression eight is slighlty north of my previous track forecast and so I have slightly adjusted my updated track forecast northward accordingly.

Intensity Forecast...No changes to the intensity forecast...I continue to show this system becoming a tropical storm in the timeframe that is now 24 hours away as the shear switches from easterly to westerly...which could allow the sheared-off thunderstorm activity to pass over the center (as we are beginning to see per the above current prognosis) and strengthen this system while the shear vector switches diretions. Weakening is then shown by 48 hours due to the expected strength of the westerly shear.

Impact Forecast...Impact swath in the above forecast graphic assumes the development of a small area of tropical storm force winds at the center per the above intensity forecast. As the cold front of the frontal cyclone coming from central Canada collides with tropical moisture pumped in by this tropical cyclone...some heavy rainfall will be possible in eastern North Carolina.

...SPECIAL FEATURE...TROPICAL DEPRESSION NINE...
Current Prognosis...While moving into the southeastern Gulf of Mexico in the last 24 hours...tropical depression nine remains situated between an upper vortex offshore of the Carolinas and another upper vortex over the western Gulf of Mexico. The upper anticyclone in between has consolidated to the south of the depression's surface center and thus the thunderstorm activity remains over Cuba and lopsided to the south side of the circulation which is laregly why this system has yet to strengthen to a tropical storm. Before sunset...visible satellite imagery suggested the surface circulation was a broad envelope with multiple tight vortices. As of 0000Z the center of the broad circulation was at 24N-85W.

Atmospheric Outlook for the Forecast Period...The upper trough currently over the northeastern US is producing an intensifying 1001 mb frontal cyclone...but this whole system at both the surface and upper-levels is too far north to bend the track of this system northward. However the upper trough and surface frontal cyclone currently over central Canada will be much more significant while arriving onto the east coast of the United States...and so if this system significantly strengthens it will become tall enough to be pulled northward and then northeastward into northwestern Florida and the southeastern United States while feeling the southwest side of this upper trough. My current forecast assumes this system will strengthen to a strong tropical storm and follow such a track as the upper anticyclone currently to the south of the center expands northward as the pair of upper vortices to the north (mentioned in the above current prognosis) weaken. This will allow the upper anticyclone to finally lower the wind shear and enhance the upper outflow of this tropical cyclone. However towards the end of the forecast period...just before landfall...conditions will become less favorable while encountering westerly shear on the north side of the upper anticyclone and south side of the upper trough which will be over the east US coast.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C waters during the forecast period. This is another reason why significant strengthening is possible during the forecast period.


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

24 Hr Forecast (0000Z Aug 31)...50 mph maximum sustained wind tropical storm centered over the eastern Gulf of Mexico at 26N-87W

48 Hr Forecast (0000Z Sep 1)...65 mph maximum sustained wind tropical storm centered in the northeastern Gulf of Mexico at 28N-87W

72 Hr Forecast (0000Z Sep 2)...45 mph maximum sustained wind tropical storm centered over southwestern Georgia at 31.5N-85W

96 Hr Forecast (0000Z Sep 3)...Vigorous remnant frontal low centered offshore of Georgia and South Carolina at 31.5N-78W

Track Forecast...The 0000Z center fix is on par with my previous forecast track and therefore I have made no changes...espeically as the 1800Z GFS computer model run from this past afternoon has become more aligned with my forecast track.

Intensity Forecast...I have lowered the overall intensity forecast as this system has not yet been able to strengthen to a tropical storm due the current lopsided structure as noted in the above current prognosis. However I have not lowered the intensity forecast for the end of the forecast period as this system becomes non-tropical...as it appears this system will align with supportive upper divergence on the east side of the upper trough associated with the frontal cyclone that will come from central Canada.

Impact Forecast...Impact swath in the above forecast graphic assumes the development of a sizeable area of tropical storm force winds at the center per the intensity forecast. The swath is lopsided to the east of the forecast track as the upper vortex in the western Gulf will limit the activity west of the storm center. This system has already produced a lot of rain across Cuba and therefore a flood risk for Cuba is expected in the short-term. By the end of the forecast period...heavy rain with flash flooding risk will be likely across Florida and parts of the southeastern United States.

...SPECIAL FEATURE...HURRICANE GASTON...
Current Prognosis...According to the National Hurricane Center and satellite observations over the last 24 hours...Gaston has weakened from its category 3 peak back down to category 2 due to an eye wall replacement cycle. This cycle was first observed by the original eye becoming crumpled and shrinking away...and now a new eye quiet larger eye has cleared open on satellite pictures. Because Gaston has essentially been stationary over the last 24 hours...it may have locally upwelled some cooler waters below the sea surface which may also explain some of the weakening. The eye of Gaston was located at 31.4N-54.7W as Gaston begins to accelerate northeast.

Atmospheric Outlook for the Forecast Period...Gaston is beginning to accelerate eastward due to deep-layered westerly flow being supplied by the intensifying 1001 mb frontal cyclone and upper trough approaching from the northeastern United States. Upper-level winds will become increasingly less favorable for Gaston over the next 48 hours as it moves into high-latitude linear (zonal) upper westerlies on the north side of the central Atlantic upper anticyclonic flow which will induce some vertical shear. The latest model runs suggest Gaston's cyclonic circulation will be able to pull down some of the cold air associated with the incoming upper trough...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 strength while moving into cooler northeastern Atlantic waters at 72 hours. Also by 72 hours...the 1027 mb ridge in the northeast Atlantic may be strong enough to bend Gaston more northward in track. The 96 to 120 hour timeframe will then be dominated by interaction with what is now the central Canada 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 96 hours while also reducing the shear. By 120 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...Water temps will be supportive for Gaston until 72 hours and beyond...when Gaston crosses the 26 deg C isotherm and ventures into and across cooler waters in the northeast Atlantic.


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

24 Hr Forecast (0000Z Aug 31)...105 mph maximum sustained wind hurricane centered at 32.5N-52.5W

48 Hr Forecast (0000Z Sep 1)...105 mph maximum sustained wind hurricane centered at 34N-45W

72 Hr Forecast (0000Z Sep 2)...85 mph maximum sustaiend wind hurricane centered just west of the Azores at 40N-35W

96 Hr Forecast (0000Z Sep 3)...60 mph maximum sustained wind tropical storm centered just north of the Azores at 40N-29W

120 Hr Forecast (0000Z Sep 4)...40 mph maximum sustained wind tropical storm with dissipating thunderstorms and transitioning into a remnant low...centered at 45N-25W

Track Forecast...The big change with the forecast track is an increase in the forecast eastward speed overall. This largely has to do with the latest model runs showing Gaston pulling down cooler air associated with the upper trough currently approaching it. With the cooler air being drawn southward and closer to warmer air to the south...this will strengthen the steering upper-level jet over Gaston which will make Gaston move faster to the east.

Intensity Forecast...Due to the apperance of a crumpling shrinking eye during my previous update...I expected Gaston would undergo and eye wall replacement cycle and hence weaken...and indeed this has occurred. Even if Gaston finishes the cycle...I do not expect re-strenghtening due to increasing westerly shear expected in the next 48 hours. I then show Gaston weakening below its current 105 mph maximum sustained wind category 2 intensity after it crosses the 26 deg C isotherm into cooler waters. But I do not show rapid dissipation of Gaston due to some supportive upper divergence expected from a local upper trough at 72 hours...followed by a reduction in shear at 96 to 120 hours...per the above atmospheric outlook section.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track. Interests in the Azores should monitor the progress of Gaston and start thinking about preparations as Gaston could spread tropical storm conditions into the area in 72 to 96 hours.

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

Current Prognosis...The tropical wave that was moving across western Africa has seen a significant increase in the intensity of its thunderstorm activity in the last 24 hours as it nears the eastern tropical Atlantic. Based on the organization of its thunderstorms at 0000Z...it appears this tropical wave is producing a brand new tropical low pressure spin centered at 14N-16W. As of 1200Z (12 hours prior) satellite pictures suggested the tropical wave axis was at 13W longitude.

Atmospheric Outlook for the Forecast Period...Although the observations in the above current prognosis suggest a 3W longitude per 12 hour (or 6W longitude per 24 hour) westward pace...I have had to adjust the later part of the track forecast below to an even faster westward pace to keep up with the latest computer model runs. Perhaps this is because the 1026 mb ridge center currently over the eastern US and 1027 mb ridge in the northeast Atlantic are expected to merge into a strong ridge over the Atlantic that will provide strong westward steering thru the forecast period. Upper-level winds are expected to be quiet favorable during the forecast period as well...with this system expected to move across a vast area of upper anticyclonic flow in the tropics that will provide low shear and good upper outflow. Thus significant strengthening is shown in the forecast below.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters during the forecast period. Latest water vapor satellite imagery suggests this system is well-embedded in a moisture field that extends into the eastern tropical Atlantic...and with wind shear expected to remain low the current assumption in the forecast below is that wind shear will not be able to advect in the dry saharan air currently seen in water vapor imagery in the central Atlantic.

24 Hr Forecast (0000Z Aug 31)...Tropical low with center moving into the southern islands of the Repbulic of Cabo Verde...centered at 14N-22W

48 Hr Forecast (0000Z Sep 1)...35 mph maximum sustained wind tropical depresison centered at 14N-28W

72 Hr Forecast (0000Z Sep 2)...50 mph maximum sustained wind tropical storm centered at 15N-36W

96 Hr Forecast (0000Z Sep 3)...75 mph maximum sustained wind hurricane centered at 16N-44W

120 Hr Forecast (0000Z Sep 4)...90 mph maximum sustained wind hurricane centered at 17N-52W

2016 Atlantic Hurricane Season Birdseye Discussion #101

By: NCHurricane2009, 6:09 AM GMT on August 29, 2016

...MONDAY AUGUST 29 2016 2:15 AM EDT...
Tropical low Invest 99-L has finally strengthened into a tropical cyclone...and is currently designated as tropical depression nine. Therefore chances are increasing that a tropical storm or hurricane could develop in the eastern Gulf of Mexico and interests in the Gulf of Mexico and southeastern United States regions inland from the Gulf coast should carefully monitor the progress of this tropical depression. See second special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression nine.

Tropical low Invest 91-L has also become a tropical cyclone while moving west-northwest toward the North Carolina coast..and is currently designated as tropical depression eight. Before recurving back out to sea...this tropical depression is likely to become a weak tropical storm over or near Cape Hatteras North Carolina over the next couple of days and thus tropical storm watches have been raised in the area. See first special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on tropical depression eight.

Gaston becomes the first major hurricane (category 3 or higher) of the 2016 Atlantic season while located well east of Bermuda...and is expected to curve eastward toward the Azores islands in the northeast Atlantic over the next few days. Therefore the Azores should carefully monitor the progress of Gaston. See third special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston.

In addition to our three 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 northwestern Gulf of Mexico...Louisiana...and southeastern Texas in the atmospheric features chart below. The National Hurricane Center has re-introduced the area of disturbed weather currently supported by an upper vortex in this region in their 48-hour tropical weather outlook. The surface trough of this disturbance has further organized into a surface low pressure spin directly below the upper vortex and just offshore of Texas. However the temperatures of the upper vortex are not cold enough to de-stabilize the atmosphere and thus showers and thunderstorms remain weak with this disturbance. Therefore tropical or subtropical cyclone formation is still not expected with this system.

The following statement concerns area of interest #2 marked over Africa in the atmospheric features chart below. A tropical wave that has moved from central to western Africa has not become any better defined or organized in satelite pictures. However some computer models suggest that in about 2 days this tropical wave will become stronger and better organized as it moves into the eastern tropical Atlantic. The GFS computer model continues to insist that this tropical wave will develop while moving across the Republic of Cabo Verde...but the Euro (ECMWF) has backed off this solution. Not yet ready to upgrade this tropical wave to a special feature with a tropical cyclone formation forecast on this blog until this tropical wave becomes better defined and organized on satellite pictures. However this remains an area worth watching in the Atlantic tropics over the next few days and interests in the Republic of Cabo Verde should 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 DEPRESSION EIGHT...
Current Prognosis...Satellite imagery continues to show the tropical depression as an exposed cloud swirl...with the sheared-off thunderstorm activity weakening at the moment. As of 0000Z this evening the center of the tropical depression passed over 32N-71.8W.

Atmospheric Outlook for the Forecast Period...Easterly and southerly vertical shear will be imparted by the upper vortex to the southwest of the tropical cyclone for the next 24 hours...with the shear later switching to westerly as the upper trough currently moving into the northeastern United States and upper trough associated with the western Canada frontal cyclone near the tropical cyclone. Although the 1026 mb surface ridge over Atlantic Canada is currently steering the tropical cyclone west-northwestward...this track will slow down and bend increasingly northward in the next 24 to 48 hours as the 1014 mb frontal cyclone intensifies over eastern Canada (in association with the upper trough currently moving into the northeastern US)...and as the vigorous frontal cyclone over western Canada follows behind...with both frontal cyclones weakening this ridge. By 72 hours...the frontal cyclone from western Canada should drive this tropical cyclone northeast and absorb it with its cold front.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 29 to 30 deg C waters during the forecast period.


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

24 Hr Forecast (0000Z Aug 30)...35 mph maximum sustained wind tropical depression centered at 33.3N-74.2W

48 Hr Forecast (0000Z Aug 31)...45 mph maximum sustained wind tropical storm centered just east of Cape Hatteras North Carolina at 35N-75W

72 Hr Forecast (0000Z Sep 1)...35 mph maximum sustained wind tropical storm centered offshore of the mid-Atlantic United States at 37.5N-73.5W becoming absorbed by a cold front

Track Forecast...No changes to the track forecast since special update #100B as the tropical depression remains on track.

Intensity Forecast...I have lowered the intensity forecast due to the currently poor satellite apperance noted in the above current prognosis section...and now only show this system becoming a tropical storm at 48 hours when the shear switches from easterly to westerly...which could allow the sheared-off thunderstorm activity to pass over the center and strengthen this system while the shear vector switches diretions. Weakening is then shown after 48 hours due to the expected strength of the westerly shear.

Impact Forecast...Impact swath in the above forecast graphic assumes the development of a small area of tropical storm force winds at the center per the above intensity forecast. As the cold front of the frontal cyclone coming from western Canada collides with tropical moisture pumped in by this tropical cyclone...some heavy rainfall will be possible in eastern North Carolina.

...SPECIAL FEATURE...TROPICAL DEPRESSION NINE...
Current Prognosis...At long last...tropical low Invest 99-L has finally organized into the ninth tropical depression of the 2016 Atlantic Hurricane Season. The tropical depression is located on the southeast side of an upper anticyclone that is between an upper vortex offshore of the Carolinas and another upper vortex over the western Gulf of Mexico. Thus northerly flow on the east side of the upper anticyclone is causing all thunderstorm bursts and bands to be lopsided to the south side of the circulation center...with this activity continuing to overspread Cuba. As of 0000Z the center of circulation was located between Florid and Cuba at 23.5N-82.5W and heading westward into the southeastern Gulf of Mexico.

Atmospheric Outlook for the Forecast Period...The upper trough currently moving into the northeastern US is producing an intensifying 1014 mb frontal cyclone over eastern Canada...but this whole system at both the surface and upper-levels will be too far north to bend the track of this system northward. However the upper trough and surface frontal cyclone currently over western Canada will be much more significant while arriving onto the east coast of the United States...and so if this system significantly strengthens it will become tall enough to be pulled northward and then northeastward into northwestern Florida and the southeastern United States while feeling the southwest side of this upper trough. My current forecast assumes this system will strengthen quickly and follow such a track as this system will soon become aligned with the favorable upper anticyclone mentioned in the above current prognosis which will lower the wind shear and enhance the upper outflow of this tropical cyclone. However towards the end of the forecast period...just before landfall...conditions will become less favorable while encountering westerly shear on the north side of the upper anticyclone and south side of the upper trough which will be over the east US coast.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C waters during the forecast period. This is another reason why significant strengthening is possible during the forecast period.


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

24 Hr Forecast (0000Z Aug 30)...45 mph maximum sustained wind tropical storm centered over the southeastern Gulf of Mexico at 24N-85W

48 Hr Forecast (0000Z Aug 31)...70 mph maximum sustained wind tropical storm centered over the eastern Gulf of Mexico at 26N-87W

72 Hr Forecast (0000Z Sep 1)...75 mph maximum sustained wind hurricane centered in the northeastern Gulf of Mexico at 28N-87W

96 Hr Forecast (0000Z Sep 2)...45 mph maximum sustained wind tropical storm centered over southwestern Georgia at 31.5N-85W

120 Hr Forecast (0000Z Sep 3)...Vigorous remnant frontal low centered offshore of Georgia and South Carolina at 31.5N-78W

Track Forecast...I have shifted the track forecast about 2W longitude compared to my previous due to the 0000Z center fix in the above current prognosis being 2W of the previous forecast.

Intensity Forecast...I have lowered the intensity forecast compared to my previous as the westward adjusted track forecast now means this system will be closer to the upper vortex in the western Gulf of Mexico. This will cause this upper vortex to limit some of the upper outflow on the west side of the tropical cyclone. By the end of the forecast period it appears this system will align with supportive upper divergence on the east side of the upper trough associated with the frontal cyclone that will come from western Canada...which will likely cause the remnants of the tropical cyclone to transition into a gale-force non-tropical remnant low along the cold front of the frontal cyclone as it moves offshore into the Atlantic.

Impact Forecast...Impact swath in the above forecast graphic assumes the development of a sizeable area of tropical storm force winds at the center per the intensity forecast. The swath is lopsided to the east of the forecast track as the upper vortex in the western Gulf will limit the activity west of the storm center. This system has already produced a lot of rain across Cuba and therefore a flood risk for Cuba is expected in the short-term. By the end of the forecast period...heavy rain with flash flooding risk will be likely across Florida and parts of the southeastern United States.

...SPECIAL FEATURE...MAJOR HURRICANE GASTON...
Current Prognosis...We now have our first major (category 3+) hurricane of the 2016 Atlantic season as Gaston has developed a well-defined eye surrounded by a symmetrical small canopy of thunderstorm activity. As of the 11 PM EDT National Hurricane Center advisory...Gaston has category 3 120 mph maximum sustained winds with a 957 mb central pressure. The eye of Gaston was located at 30.6N-55.1W

Atmospheric Outlook for the Forecast Period...Gaston has stalled while getting trapped between the 1028 mb Atlantic ridge to the northeast and 1026 mb ridge entering the northwestern Atlantic from Atlantic Canada. However the intensifying 1014 mb frontal cyclone over eastern Canada will weaken the 1026 mb ridge as it enters the Atlantic...with a second frontal cyclone currently over western Canada will following behind. Both frontal cyclones and high-latitude upper westerly flow will cause Gaston to turn eastward after 24 hours. The 1028 mb ridge to the northeast may be strong enough towards the end of the 120-hour forecast period to cause Gaston to bend more northeastward in track.

Thermodynamic Outlook for the Forecast Period...Gaston is currently over favorable 29 to 30 deg C water temps...but by the end of the 120-hour forecast period the hurricane will have crossed the 26 deg C isotherm into cooler waters.


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

24 Hr Forecast (0000Z Aug 30)...120 mph maximum sustained wind hurricane centered at 31N-55.1W

48 Hr Forecast (0000Z Aug 31)...115 mph maximum sustained wind hurricane centered at 32.5N-53W

72 Hr Forecast (0000Z Sep 1)...115 mph maximum sustained wind hurricane centered at 34N-47W

96 Hr Forecast (0000Z Sep 2)...90 mph maximum sustaiend wind hurricane centered at 37N-40W

120 Hr Forecast (0000Z Sep 3)...75 mph maximum sustained wind hurricane centered just west of the Azores at 39N-35W

Track Forecast...Because Gaston has stalled and is expected to move only slowly northward in the next 24 hours...I have had to adjust my forecast track more south when compared to my previous. Gaston will either pass over or just north of the Azores in about 5 or 6 days and therefore interests should pay careful attention to Gaston.

Intensity Forecast...I currently assume Gaston will not strengthen further in the next 24 hours either due to an eyewall replacement cycle or perhaps as it upwells cooler waters due to the fact it has stalled out (however these sorts of effects are hard to predict and therefore it is conceivable that Gaston strengthens even more). After 24 hours...Gaston will encounter less favorable linear (zonal) westerly shearing flow in the higher latitudes which will more likely limit additional strengthening and instead begin weakening the hurricane. By 120 hours...low-level southerly flow ahead of the frontal cyclone from western Canada will cause warm air advection and hence upper ridging to build across the north Atlantic and over Gaston...once again reducing the shear over Gaston. However I still forecast weakening by that time as Gaston will have reached waters below 26 deg C.

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

2016 Atlantic Hurricane Season Birdseye Discussion #100B (Special Update)

By: NCHurricane2009, 8:18 PM GMT on August 28, 2016

...SUNDAY AUGUST 28 2016 4:20 PM EDT...
Tropical low Invest 91-L quickly strengthens into the eighth tropical depression of the 2016 Atlantic Hurricane Season while moving west-northwestward toward the North Carolina coastline. As such tropical storm watches or warnings may go up at anytime on parts of the North Carolina coast. See special feature section below for an initial assessment of tropical depression eight.

See full discusssion #100 for an update on the rest of the Atlantic tropics. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston and newly-formed tropical depression eight.

...SPECIAL FEATURE...TROPICAL DEPRESSION EIGHT...
Current Prognosis...Tropical low Invest 91-L has strengthened into the eighth tropical depression of the 2016 Atlantic Hurricane Season while currently moving west-northwestward toward the North Carolina coast. Satellite imagery shows the tropical depression as an exposed cloud swirl with a large circular thunderstorm burst to the west of the swirl. This is because the tropical depression is under easterly vertical shear induced by the upper vortex to its immediate southwest. As of 1800Z this afternoon the center of the tropical depression passed over 31.6N-70.5W...and three hours prior at 1500Z it passed over 31.3N-70W.

Atmospheric Outlook for the Forecast Period...Easterly and southerly vertical shear will be imparted by the upper vortex to the southwest of the tropical cyclone for the next 24 hours...with the shear switching to westerly as the upper trough currently moving into the northeastern United States and upper trough associated with the western Canada frontal cyclone near the tropical cyclone. Although a surface ridge over the northeastern US and northwestern Atlantic is currently steering the tropical cyclone west-northwestward...this track will slow down and bend increasingly northward in the next 24 to 48 hours as a frontal cyclone develops and intensifies over eastern Canada (in association with the upper trough currently moving into the northeastern US)...and as the vigorosu frontal cyclone over western Canada follows behind...with both frontal cyclones weakening this ridge. By 72 hours...the frontal cyclone from western Canada should drive this tropical cyclone northeast and absorb it with its cold front.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 29 to 30 deg C waters during the forecast period.


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

24 Hr Forecast (1800Z Aug 29)...40 mph maximum sustained wind tropical storm centered at 33N-74W

48 Hr Forecast (1800Z Aug 30)...50 mph maximum sustained wind tropical storm centered just southeast of Cape Hatteras North Carolina at 34N-75W

72 Hr Forecast (1800Z Aug 31)...40 mph maximum sustained wind tropical storm centered offshore of the mid-Atlantic United States at 37N-74W becoming absorbed by a cold front

Track Forecast...Although the above current prognosis suggests this system is moving at 0.5W longitude per 3 hours (or 4W longitude per day)...the above track forecast shows this system slowing down from this current pace in the next 24 to 48 hours due to the steering surface ridge weakening...and then by 72 hours the track is expected to turn northeastward.

Intensity Forecast...I show slow strengthening into a tropical storm in the next 24 hours as this system has managed to slowly strengthen in the current shear environment. As the shear switches from easterly to westerly in 48 hours...I show a little more rapid strengthening as the ball of thunderstorms will have a chance to pass over the center while the shear vector switches directions. Weakening is shown after 48 hours due to the expected strength of the westerly shear.

Impact Forecast...Impact swath in the above forecast graphic assumes the development of a small area of tropical storm force winds at the center per the above intensity forecast. As the cold front of the frontal cyclone coming from western Canada collides with tropical moisture pumped in by this tropical cyclone...some heavy rainfall will be possible in eastern North Carolina.

2016 Atlantic Hurricane Season Birdseye Discussion #100A (Special Update)

By: NCHurricane2009, 5:30 PM GMT on August 28, 2016

...SUNDAY AUGUST 28 2016 1:30 PM EDT...
Tropical low Invest 91-L quickly strengthens into the eighth tropical depression of the 2016 Atlantic Hurricane Season while moving west-northwestward toward the Carolina coastline. As such tropical storm watches or warnings may go up at anytime on the Carolina coast. I will be issuing another speical update later this afternoon with a forecast for the newly-formed tropical cyclone.

See full discusssion #100 for an update on the rest of the Atlantic tropics. Visit www.nhc.noaa.gov for up to the minute latest information on Hurricane Gaston and newly-formed tropical depression eight.

2016 Atlantic Hurricane Season Birdseye Discussion #100

By: NCHurricane2009, 4:26 AM GMT on August 28, 2016

...SUNDAY AUGUST 28 2016 12:30 AM EDT...
Alert! Interests in the Gulf of Mexico and southeastern United States regions inland from the Gulf coast should carefully monitor the progress of tropical disturbance Invest 99-L...read the statement for area of interest #2 and see the first special feature section below for details.

Gaston regains hurricane strength in earnest and could gain major hurricane (category 3 or higher) strength while passing east of Bermuda over the next couple of days. See second special feature section below for additional details on Gaston and visit www.nhc.noaa.gov for up to the minute latest information on Gaston.

The following statement concerns area of interest #1 marked just southwest of Bermuda in the western Atlantic in the atmospheric features chart below. Tropical low Invest 91-L is beginning to move west-northwest toward the Carolina coast while steered by the 1022 mb ridge currently over the northeastern United States. Although atmospheric conditions remain favorable as the nearby upper trough has split into an upper vortex to the southwest moving away and another fragment moving eastward and away...its shower and thunderstorm activity remains rather weaker presumably due to nearby dry sinking air produced by convergence on the west side of the upper vortex. Also by 48 hours as this system nears the Carolina coast...unfavorable westerly vertical shear could increase as the upper trough currently over the central US nears...and also as another upper trough currently over western Canada also nears. Therefore the window for this system to develop is small and thus I have not upgraded it to a special feature with a tropical cyclone formation forecast on this blog.

The following statement concerns area of interest #2 marked over Cuba...the Bahamas...and south Florida in the atmospheric features chart below. Tropical disturbance Invest 99-L has regained organization as the unfavorable upper trough in the region has already broken up...and therefore chances for a significant tropical storm or hurricane to develop in the Gulf of Mexico have increased. Therefore it is paramount that interests in the Gulf of Mexico and southeastern United States regions inland from the Gulf carefully monitor the progress of this tropical disturbance. See first special feature section below for additional details on this situation.

The following statement concerns area of interest #3 marked over the northwestern Gulf of Mexico and Louisiana in the atmospheric features chart below. The showers and thunderstorms that developed in the central Gulf over the last couple of days have wrapped into a comma shape while becoming maintained by upper divergence on the east side of an upper vortex lifting northward from the southern Gulf and into the norhtwestrn Gulf. In addition a surface trough has developed in this activity...but the strongest part of the disturbance has made landfall in Louisiana and therefore tropical cyclone formation is not expected. This is my final statement on this blog on this disturbance.

The following statement concerns area of interest #4 marked over Africa in the atmospheric features chart below. Satellite animation suggests there is a tropical wave with cyclonic turning and loosely-packed showers and thunderstorms over central Africa moving into southern Mali. Computer models suggest that in about 3 days this tropical wave will become stronger and better organized as it moves into the eastern tropical Atlantic...with the GFS and European (ECMWF) models continuing to insist that this tropical wave will develop while moving across the Republic of Cabo Verde. Not yet ready to upgrade this tropical wave to a special feature with a tropical cyclone formation forecast on this blog until this tropical wave becomes better defined and organized on satellite pictures. However with such strong computer model support...this is an area worth watching in the Atlantic tropics over the next few days and interests in the Republic of Cabo Verde should 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 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 LOW INVEST 99-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...As of this evening the tropical low pressure spin of disturbance Invest 99-L has seperated from its parent tropical wave...with the parent wave currently over the western Caribbean and Central America. The lengthy upper trough that was suppressing this disturbance has split into two upper vortices...one over the western Gulf of Mexico and another southwest of Bermuda. Upper anticyclonic flow with low shear and good upper outflow has begun to develop over this disturbance and in between these two upper vortices...and therefore tropical cyclone formation is becoming more likely again. Showers and thunderstorms have once again increased and have started to become better organized over and around the tropical low pressure center while covering Cuba...the Bahamas...and south Florida. As of 0000Z the center was located on the north coast of Cuba at 22.3N-78W. Satellite animation suggests this system is moving rather slowly west-northwest while only covering 0.5W longitude in 6 hours (roughly a rate of 2W per 24 hours). Thus the early part of the track forecast listed below is based on a 2 to 2.5W per 24 hour rate of progression.

Atmospheric Outlook for the Forecast Period...The upper trough currently over the central US will produce a frontal cyclone over eastern Canada shortly...but this whole system at both the surface and upper-levels will be too far north to bend the track of this system northward. However the upper trough and surface frontal cyclone currently over western Canada will be much more significant while arriving onto the east coast of the United States...and so if this system significantly strengthens it will become tall enough to be pulled northward and then northeastward into northwestern Florida and the southeastern United States while feeling the southwest side of this upper trough. My current forecast below assumes this system will strengthen rapidly and follow such a track as computer models now show the favorable upper anticyclone currently developing over this system (mentioned in the above current prognosis) expanding with time. However at the end of the forecast period...just before landfall...conditions will become less favorable while encountering westerly shear on the north side of this upper anticyclone and south side of the upper trough which will be over the east US coast.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C waters during the forecast period. This is another reason why significant strengthening is possible during the forecast period.

24 Hr Forecast (0000Z Aug 29)...Organized tropical low centered on the north coast of Cuba and south of Florida at 23N-80.5W

48 Hr Forecast (0000Z Aug 30)...45 mph maximum sustained wind tropical storm centered over the southeastern Gulf of Mexico and west-southwest of the Florida Keys at 24N-83W

72 Hr Forecast (0000Z Aug 31)...75 mph maximum sustained wind hurricane centered over the eastern Gulf of Mexico at 26N-85W

96 Hr Forecast (0000Z Sep 1)...90 mph maximum sustained wind hurricane centered in the northeastern Gulf of Mexico at 28N-85.5W

120 Hr Forecast (0000Z Sep 2)...60 mph maximum sustained wind tropical storm centered over southern Georgia centered at 31.5N-83W

...SPECIAL FEATURE...HURRICANE GASTON...
Current Prognosis...Gaston's satellite appearance has improved while producing a circular area of thunderstorms now seperate from the cloudiness associated with the upper vortex to its southwest. Although the upper trough that was over the western Atlantic near Bermuda is now passing just north of Gaston...Gaston's thunderstorms have been strong enough to support a warm core upper anticyclone that has prevented the upper trough from shearing it. At times an eye has popped open on satellite imagery and thus Gaston is now back to hurricane status. As of 0000Z satellite imagery suggested the center of Gaston was over 29.2N-54W in the central Atlantic.

Atmospheric Outlook for the Forecast Period...Gaston's track has started bending northwestward and is beginning to slow down while getting trapped into the armpit between the 1025 mb Atlantic ridge to the northeast and 1022 mb ridge about to enter the northwestern Atlantic from the northeastern United States. Later in the forecast period...divergence on the east side of the upper trough currently over the central US will strengthen what's left of low surface pressures over northeastern Canada's Hudson Bay...resulting in a frontal cyclone that will push out the aforementioned 1022 mb ridge. A second frontal cyclone currently over western Canada will soon follow behind. Both frontal cyclones and high-latitude upper westerly flow will cause Gaston to turn eastward after 48 hours. The 1025 mb ridge to the northeast may be strong enough towards the end of the 120-hour forecast period to cause Gaston to bend more northeastward in track.

Thermodynamic Outlook for the Forecast Period...Gaston is currently over favorable 29 to 30 deg C water temps...but by the end of the 120-hour forecast period the hurricane will be approaching the cooler 26 deg C isotherm.


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

24 Hr Forecast (0000Z Aug 29)...100 mph maximum sustained wind hurricane centered at 31.5N-56W

48 Hr Forecast (0000Z Aug 30)...115 mph maximum sustained wind hurricane centered at 33N-56W

72 Hr Forecast (0000Z Aug 31)...115 mph maximum sustained wind hurricane centered at 34N-53W

96 Hr Forecast (0000Z Sep 1)...115 mph maximum sustained wind hurricane centered at 36N-47W

120 Hr Forecast (0000Z Sep 2)...90 mph maximum sustaiend wind hurricane centered at 39N-41W

Track Forecast...Gaston is beginning to slow down while becoming trapped in the armpit between the 1025 mb Atlantic ridge to the northeast and 1022 mb ridge about to enter the northwestern Atlantic from the northeastern United States...which will prevent Gaston from going as far north and west as my previous forecast showed. Therefore my updated forecast track is an eastward adjustment compared to the previous.

Intensity Forecast...The initial state of Gaston is better than I previously predicted with Gaston avoiding shear from the upper trough passing by to its north per the above current prognosis. Also with the updated track forecast showing Gaston taking longer to reach the more northern latitudes...Gaston will have more time in the favorable upper anticyclonic flow behind the upper trough before reaching the less favorble linear (zonal) westerly shearing flow in the higher latitudes. Therefore I have raised the intensity forecast significantly..and in fact Gaston has the chance of becoming a major hurricane (115+ mph maximum sustained winds) before getting affected by westerly shear and cooler waters by the end of the 120-hour forecast period.

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

2016 Atlantic Hurricane Season Birdseye Discussion #99

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

...FRIDAY AUGUST 26 2016 11:50 PM EDT...
Tropical Storm Gaston expected to regain hurricane strength while passing east of Bermuda this weekend. Expect surf and rip currents to increase on the shores of Bermuda as Gaston passes by. See special feature section below for additional details on Gaston and visit www.nhc.noaa.gov for up to the minute latest information on Gaston.

The following statement concerns area of interest #1 marked just south of Bermudain the western Atlantic in the atmospheric features chart below. The tail end of the cold front that absorbed the remnants of Tropical Storm Fiona has spun up into a surface tropical low designated as Invest 91-L. This has occurred due to supporting divergence on the east side of the lengthy upper trough associated with this front...but also due to supporting upper outflow supplied a small upper anticyclone ahead of the front (with this upper anticyclone also providing a low shear environment which in turn is allowing for some organization of this new tropical low). The 1022 mb ridge currently over the north-central US will soon pass north of this tropical low which will steer it west-northwest toward the Carolina coast over the next 72 hours. During the first 48 hours of this timeframe...atmospheric conditions will remain favorable for development as the aformentioned and unfavorable lengthy upper trough will split into an upper vortex that moves westward and away and another fragment that moves eastward and away...thus interests at the Carolina coast should monitor this system. However I have not upgraded this system to a special feature with a tropical cyclone formation forecast as its thunderstorms have weakened tonight presumably due to a small patch of dry sinking air to its west caused by upper convergence on the west side of the upper trough. And also by 72 hours as this system nears the Carolina coast...unfavorable westerly vertical shear could increase as the upper trough currently over the western US nears...and also as another upper trough currently over western Canada also nears.

The following statement concerns area of interest #2 marked over the north-central Caribbean region in the atmospheric features chart below. Tropical disturbance Invest 99-L remains less organized due to a barrier of unfavorable upper-level winds created by the upper trough in the western Atlantic currently near Bermuda linking up with the upper trough currently over the southern Gulf of Mexico. Therefore chances remain low that Invest 99-L will develop. However will continue to monitor this disturbance as it moves across Cuba and south Florida and into the Gulf of Mexico over the weekend due to the fact that the linked upper troughs are forecast to break up into pieces.

The following statement concerns area of interest #3 marked over the Gulf of Mexico in the atmospheric features chart below. Showers and thunderstorms continue in this area while supported by upper divergence on the southwest side of an upper anticyclone centered over the southeastern United States. Recently this activity has increased in intensity. This is due to the fact that a lobe of upper vorticity from the upper trough currently in the western Atlantic has retrograded westward along the south side of the upper anticyclone and into northwestern Florida...with supporting upper divergence over the Gulf of Mexico becoming very high between the west side of this upper vortex and another upper trough currently over the southern Gulf of Mexico. Despite the increase in activity...there remain no signs of a surface low pressure spin developing...and computer models do not forecast tropical cyclone formation from this area.

The following statement concerns area of interest #4 marked over Africa in the atmospheric features chart below. Computer models suggest that in about 4 days a tropical wave currently over central Africa will become stronger and better organized as it moves into the eastern tropical Atlantic...with the GFS and European (ECMWF) models continuing to insist that this tropical wave will develop. Not yet ready to upgrade this tropical wave to a special feature with a tropical cyclone formation forecast on this blog until this tropical wave becomes better defined and organized on satellite pictures as it approaches the eastern tropical Atlantic. However with such strong computer model support...this is an area worth watching in the Atlantic tropics 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 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 GASTON...
Current Prognosis...Tropical Storm Gaston continues to have the apperance of a tropical cyclone entangled with the upper vortex to its immediate southwest while it produces circular storm bursts and spiral bands within a larger east-west band of thunderstorms supported by divergence on the northeast side of the upper vortex. The tropical storm has re-gained some organization and stopped weakeing...holding a steady strength of 65 mph maximum sustained winds. As of 0000Z satellite imagery suggested the center of Gaston passed near 26N-50W in the central Atlantic.

Atmospheric Outlook for the Forecast Period...Gaston's track has started bending more westward while reaching easterly atmospheric flow on the north side of the central Atlantic upper vortex and south side of the 1024 to 1026 mb Atlantic surface ridge. By 48 to 72 hours...Gaston is expected to stay east of Bermuda while bending northward toward a ridge weakness associated with the 1006 mb frontal cyclone currently over southeastern Canada as this frontal cyclone moves and strengthens across the north Atlantic. What's left of the frontal cyclone currently over northeastern Canada afterwards will finish the job of turning Gaston northward while moving into the northwestern Atlantic by 72 hours...with both this frontal cyclone and high-latitude upper westerly flow causing Gaston to turn eastward by 96 hours.

Thermodynamic Outlook for the Forecast Period...This system is currently moving into a maximum of rather favorable 29 to 30 deg C waters...but by the end of the 120-hour forecast period Gaston will be approaching the cooler 26 deg C isotherm if my current track forecast holds.


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

24 Hr Forecast (0000Z Aug 28)...60 mph maximum sustained wind tropical storm centered at 28N-55W

48 Hr Forecast (0000Z Aug 29)...75 mph maximum sustained wind hurricane centered at 31.5N-59W

72 Hr Forecast (0000Z Aug 30)...85 mph maximum sustained wind hurricane centered at 35N-61W

96 Hr Forecast (0000Z Aug 31)...75 mph maximum sustained wind hurricane centered at 35.5N-55W

120 Hr Forecast (0000Z Sep 1)...65 mph maximum sustained wind tropical storm centered at 36N-50W

Track Forecast...The 0000Z center fix in the above current prognosis suggests Gaston is essentially along my previous forecast track and therefore my updated track is an extension of my previous forecast. However in my next update I may have to shift the track forecast eastward as the latest model runs over the last couple of days have been shifting east. This is because the latest model runs now show Gaston ceasing westward progress in the short-term while becoming trapped in an armpit between the current 1024 to 1026 mb Atlantic surface ridge and 1022 mb ridge currently over the north-central US as this ridge moves into the northwest Atlantic.

Intensity Forecast...I still show Gaston weakening to 60 mph maximum sustained winds in the short-term as I still forecast that the upper trough currently near Bermuda will induce a burst of unfavorable northerly and westerly shear while passing just north of Gaston. At 48 hours the upper flow behind this upper trough will be much more favorable while being anticyclonic in nature (which will reduce the shear and enhance the upper outflow of the storm)...and this is when I forecast Gaston to become a hurricane again. I have upped the intensity for 72 hours as the latest GFS model run shows a slighlty larger area of upper anticyclonic flow such that Gaston is still in this flow at that forecast position. By 96 and 120 hours...this system will reach less favorable linear (zonal) upper westerlies on the north side of the anticyclonic flow which will cause vertical shear. However I only show gradual weakening as the eastward acceleration of the storm at 96 to 120 hours will allow the forward storm motion to somewhat match the zonal upper westerlies...making the shear not as bad for Gaston.

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

2016 Atlantic Hurricane Season Birdseye Discussion #98

By: NCHurricane2009, 12:00 PM GMT on August 26, 2016

...FRIDAY AUGUST 26 2016 8:00 AM EDT...
Gaston weakens back to a tropical storm while interacting with a central Atlantic upper vortex. Although Gaston has weakened...interests in Bermuda should continue to monitor the progress of Gaston as it will pass close to the island this weekend. See special feature section below for additional details on Gaston and visit www.nhc.noaa.gov for up to the minute latest information on Gaston.

The following statement concerns area of interest #1 marked southwest of Bermuda in the western Atlantic in the atmospheric features chart below. The remnants of Tropical Storm Fiona have lost their identity along the tail end of a cold front moving across the Atlantic and therefore this is my final statement on the remnants of Fiona.

The following statement concerns area of interest #2 marked over the north-central Caribbean region in the atmospheric features chart below. Tropical wave Invest 99-L has become less organized due to land interaction with Haiti and the Dominican Republic...and the upper trough in the western Atlantic currently near Bermuda is beginning to link up with the upper trough currently over the southern Gulf of Mexico. Combined with the weakened state of the tropical wave's thunderstorms...there will likely not be enough thunderstorm latent heat release to break up the combining upper troughs and thus the combining upper troughs are likely to suppress this tropical wave from developing. Will continue to monitor this tropical wave as it moves aross Cuba and south Florida and into the Gulf of Mexico this weekend...but I have cancelled it as a special feature on this blog as it chances of tropical cyclone formation have reduced.

The following statement concerns area of interest #3 makred over the Gulf of Mexico in the atmospheric features chart below. The National Hurricane Center in their 48-hour tropical weather outlook highlighted some showers and thunderstorms over this area...and this activity is supported by upper divergence on the southwest side of an upper anticyclone currently over the southeastern United States. This activity is weak...there are no signs of a surface low pressure spin developing...and computer models do not forecast tropical cyclone formation from this area.

The following statement concerns area of interest #4 marked over Africa in the atmospheric features chart below. Computer models suggest that in about 5 days a tropical wave currently over central Africa will become stronger and better organized as it moves into the eastern tropical Atlantic...with the GFS and European (ECMWF) models continuing to insist that this tropical wave will develop. Not yet ready to upgrade this tropical wave to a special feature with a tropical cyclone formation forecast on this blog until this tropical wave becomes better defined and organized on satellite pictures as it approaches the eastern tropical Atlantic. However with such strong computer model support...this is an area worth watching in the Atlantic tropics over the next few days.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z and 0729Z-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 temperature isotherms at http://www.nhc.noaa.gov/satellite.php...the site from which the above thermo chart is generated from...are currently unavailable. Therfore I have used the 26 deg C isotherm from the thermodynamics chart in previous discussion #97. 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 GASTON...
Current Prognosis...Gaston has lost its hurricane strength within the last 24 hours while interacting with the east side of an upper vortex in the central tropical Atlantic. It appears the unfavorable southerly vertical shear applied by the upper vortex has been a bit stronger than I previously anticipated. But also the cloud field and also the tropical storm wind field of Gaston has expanded during this weakening process...perhaps as Gaston has become larger and broader due to widespread surface pressure falls induced by the divergence on the east side of the upper vortex. The broadened size of Gaston may have caused the surface low pressure gradient within the storm to lessen which in turn would also cause the winds to weaken. Currently Gaston appears increasingly less organized and has the apperance of a tropical storm entangled with the upper vortex to the west. As of 0600Z satellite imagery suggested the center of Gaston was located in the central Atlantic at 23.2N-46W.

Atmospheric Outlook for the Forecast Period...During the first part of the forecast period...Gaston's track will bend more westward toward Bermuda while reaching easterly atmospheric flow on the north side of the central Atlantic upper vortex and south side of 1025 mb Atlantic ridge. However by 72 to 96 hours...Gaston is expected to stay east of Bermuda while bending northward toward a ridge weakness associated with the 1006 mb frontal cyclone currently over southeastern Canada as this frontal cyclone moves and strengthens across the north Atlantic. What's left of the frontal cyclone currently over northeastern Canada will finish the job of turning Gaston northward while moving into the northwestern Atlantic by 96 hours...with both this frontal cyclone and high-latitude upper westerly flow causing Gaston to turn eastward by 120 hours.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters on the current forecast track...reaching a maximum of 29 to 30 deg C waters by 48 to 72 hours...then reaching 27 to 28 deg C waters by 120 hours.


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

24 Hr Forecast (0600Z Aug 27)...60 mph maximum sustained wind troipcal storm centered at 26.5N-51W

48 Hr Forecast (0600Z Aug 28)...60 mph maximum sustained wind tropical storm centered at 29N-56W

72 Hr Forecast (0600Z Aug 29)...75 mph maximum sustained wind hurricane centered at 32.5N-59.5W

96 Hr Forecast (0600Z Aug 30)...75 mph maximum sustained wind hurricane centered at 35.5N-60W

120 Hr Forecast (0600Z Aug 31)...65 mph maximum sustained wind tropical storm centered at 36N-54W

Track Forecast...The 0600Z center fix in the above current prognosis suggests Gaston is essentially along my previous forecast track and therefore my updated track is an extension of my previous forecast.

Intensity Forecast...I have significantly lowered the intensity forecast for Gaston as the central Atlantic upper vortex has had a more adverse effect on the tropical storm per the above current prognosis. I keep Gaston below hurricane strength through 48 hours as I now believe its thunderstorm latent heat release will not be enough to weaken the upper trough currently in the northwestern Atlantic near Bermuda...and instead this upper trough may produce additional unfavorable shearing as it passes just north of Gaston. By 72 hours the upper flow behind this upper trough will be much more favorable while being anticyclonic in nature (which will reduce the shear and enhance the upper outflow of the storm)...and combined with the 29 to 30 deg C water temp maximum mentioned in the above thermodynamic outlook...this is when I forecast Gaston to become a hurricane again. But by 96 and 120 hours...this system will reach less favorable linear (zonal) upper westerlies on the north side of the anticyclonic flow which will cause vertical shear. However I only show gradual weakening as the eastward acceleration of the storm by 120 hours will allow the forward storm motion to somewhat match the zonal upper westerlies...making the shear not as bad for Gaston.

Impact Forecast...Impact swath is an extrapolation of the 5 AM EDT NHC tropical storm wind radius along my forecast track.

2016 Atlantic Hurricane Season Birdseye Discussion #97

By: NCHurricane2009, 5:14 AM GMT on August 25, 2016

...THURSDAY AUGUST 25 2016 1:15 AM EDT...
Interests in Bermuda should read the statement below about Hurricane Gaston and interests in the Dominican Republic...Haiti...Cuba...the Bahamas...south Florida...and Gulf of Mexico should read the statement below about area of interest #2.

Tropical Storm Gaston strengthens into the third hurricane of the 2016 Atlantic season. The late part of the forecast track has shifted westward closer to Bermuda and thus interests in Bermuda should very carefully watch Gaston as Gaston is likely to strengthen into a major hurricane (category 3 or higher). See second special feature section below for additional details on Gaston and visit www.nhc.noaa.gov for up to the minute latest information on Gaston.

The following statement concerns area of interest #1 marked south of Bermuda in the western Atlantic in the atmospheric features chart below. The remnants of Fiona have seen an increase in the intensity and organization of its showers and thunderstorms while sliding underneath a more favorable upper anticyclone supplying low shear and upper outflow near Bermuda. However it has not regenerated into a tropical cyclone and thus I have cancelled it as a special feature on this blog as it will soon encounter another round of unfavorble vertical shear from an upper trough fragment to its west. As the remnants continue to drift westward toward the southeastern United States...it will once again encounter more favorable conditions in 36 hours as the upper anticyclone over the southeastern US moves offshore into the Atlantic. Thus will continue to monitor the remnants of Fiona.

The following statement concerns area of interest #2 marked over the northeastern Caribbean region in the atmospheric features chart below. Although vigorous tropical wave Invest 99-L has developed tropical storm force winds...its circulation has become less organized while featuring multiple spins and thus doesn't qualify as a tropical storm at this time. There remains large uncertainty on the future strength of this system...and thus interests in the Dominican Republic...Haiti...Cuba...the Bahamas...south Florida...and Gulf of Mexico should carefully watch this system. See first special feature section below for additional details. Regardless of tropical cyclone formation or not...these areas can expect vigorous weather (gusty winds with heavy rain...with the possibility of flash flooding) 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 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...NORTHEASTERN CARIBBEAN TROPICAL WAVE INVEST 99-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...Although aircraft reconaissance this past afternoon revealed the devleopment of tropical storm force winds in tropical wave Invest 99-L as it overspread the northeastern Caribbean Sea Islands...no well-defined close circulation was found to upgrade this system to a tropical storm and indeed the satellite presentation has become less organized this evening. The center of the poorly-organized low pressure spin appeared to be located along the north coast of Puerto Rico as of 0000Z...at 18N-66W. Just to get an idea of how poorly-organized this system is at the moment...visible satellite just before sunset suggested there was a seperate tight cloud swirl to the north of the aforementioned center...and perhaps there is another center further west near the Dominican Republic where a comma-shaped storm mass has been developing last this afternoon and through this eveing. The aforementioned 0000Z center fix is 1 degree latitude further north and 2 degrees longitude further west than my prior forecast...but I've only adjusted the updated forecast westward and not northward as the lastest satellite animation suggests little northward progress such that I still expect the center to move along or very near the north coast of the Dominican Republic and Haiti. Regardless of tropical cyclone formation or not...vigorous weather (gusty winds with heavy rainfall...with possible flash flooding risk) will continue over Puerto Rico over the next 24 hours...and overspread Haiti...the Dominican Republic...Cuba...the Bahamas...and south Florida over the next 48 hours.

Atmospheric Outlook for the Forecast Period...The low pressure field of Fiona's remnants and divergence on the east side of the upper trough currently east of North Carolina are expected to create a low-level ridge weakness that will cause this tropical wave to generally bend northward in track such that it moves across the northern Caribbean islands...Bahamas...and toward south Florida for the first part of the 120-hr forecast period. By the late part of the forecast period...low-level ridging building across the United States behind the 1006 mb frontal cyclone currently over south-central Canada/north-central United States is likely to bend the track more westward as this system moves into the Gulf of Mexico. Currently this tropical wave's favorable warm core upper anticyclone has become strong due to the latent heat release of its thunderstorm activity. The strength of the upper anticyclone has broken up the unfavorable western Atlantic upper vorticity that was just to the north...with what's left of the upper vorticity merging with the western Caribbean upper trough to the west and central Atlantic upper vortex to the northeast. Despite this...I have lowered the intensity forecast for the next 48 hours based on the less organized satellite appearance and expected land interaction with Haiti and the Dominican Republic which could keep it disorganized for a bit longer. The intensity forecast through 96 hours is then kept the same...but remains conservative due to uncertainty in how the upper trough currently east of North Carolina will interact with the upper trough in the western Caribbean. One possibility is that this system maintains a small and highly favorable upper anticyclone between these upper troughs...in which case significant strengthening is possible. Or alternatively the upper troughs link up...which would shear off the favorable upper anticyclone and ultimately suppress this system. But by 120 hours...I start to show some brisk strengthening as the GFS computer model...which somewhat shows the upper troughs linking up...then shows the upper troughs breaking up by that time.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C waters during the forecast period. Therefore if this system reaches a favorable atmospheric environment...some signficant strengthening more than shown in the forecast below is possible.

24 Hr Forecast (0000Z Aug 26)...Tropical low centered just north of the Haiti/Dominican Republic border at 20N-72W

48 Hr Forecast (0000Z Aug 27)...Tropical low centered between the Bahamas and Cuba at 22.5N-76W

72 Hr Forecast (0000Z Aug 28)...45 mph maximum sustained wind tropical storm centered over the Florida Keys at 24N-81W

96 Hr Forecast (0000Z Aug 29)...45 mph maximum sustained wind tropical storm centered over the eastern Gulf of Mexico at 26N-86W

120 Hr Forecast (0000Z Aug 30)...60 mph maximum sustained wind tropical storm centered over the northwestern Gulf of Mexico at 27N-91W

...SPECIAL FEATURE...HURRICANE GASTON...
Current Prognosis...As expected Gaston has been steadily intensifying and is now the third hurricane of the 2016 Atlantic season. As of 0000Z Gaston was in the central tropical Atlantic while centered at 18.2N-41W and has the classic satellite apperance of a hurricane poised for additional strengthening with a circular core of spiral thunderstorm bands.

Atmospheric Outlook for the Forecast Period...Gaston has become strong and tall enough to be steered by the central Atlantic cut-off upper vortex (marked by blue L to the northwest of Gaston in the above atmospheric features chart)...which has resulted in a northward jump in the storm track. Some less favorable southerly vertical shear imparted by the east side of the upper vortex may slow the strengthening rate of this system during the 24 to 48 hour timeframe. By 48 to 72 hours...Gaston will have reached the north side of the upper vortex...which combined with the south side of the 1026 mb Atlantic surface ridge will cause Gaston to swing back to a more westward track. By 96 hours...Gaston is expected to bend northward in track again while it begins to get pulled into a ridge weakness associated with the 1006 mb frontal cyclone currently over south-central Canada/north-central US as this frontal cyclone moves and strengthens across the north Atlantic. However the latest model runs suggest this ridge weakness will not be strong enough to fully bend the track of Gaston northward. Instead Gaston will have to wait for what's left of the 993 mb frontal cyclone over eastern Canada to move into the northwest Atlantic and finish the job. Thus with a delayed northward turn now forecast...Gaston could reach closer to Bermuda than previously thought and interests in Bermuda should carefully watch Gaston.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters on the current forecast track...reaching a maximum of 29 to 30 deg C waters by 72 to 96 hours...then reaching 28 deg C waters by 120 hours.


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

24 Hr Forecast (0000Z Aug 26)...95 mph maximum sustained wind hurricane centered at 22.5N-45W

48 Hr Forecast (0000Z Aug 27)...105 mph maximum sustained wind hurricane centered at 26N-50W

72 Hr Forecast (0000Z Aug 28)...130 mph maximum sustained wind hurricane centered at 28N-55W

96 Hr Forecast (0000Z Aug 29)...140 mph maximum sustained wind hurricane centered at 31.5N-59W

120 Hr Forecast (0000Z Aug 30)...135 mph maximum sustained wind hurricane centered at 35N-61W

Track Forecast...Computer model runs yesterday shifted to a northward turn toward the central Atlantic upper vortex sooner and indeed this has materialized...resulting in Gaston being quiet further northeast of my previous forecast track as of the 0000Z center fix. Thus I have updated the early part of my forecast to be northeast of my previous...and then I have updated the later part of the forecast to be more west of my previous per the above atmospheric outlook section. Because the 0000Z center fix is a bit east of where the GFS 1800Z computer model run put Gaston by 0000Z...my updated forecast track is essentially based on being slightly east of the 1800Z GFS model run.

Intensity Forecast...I have lowered the early part of the intensity forecast based on Gaston taking a bit longer to reach hurricane strength...but I kept the later part of the intensity forecast the same as the northeast shift in the early part of the forecast track means Gaston will be further away from the unfavorable shearing effects of the central Atlantic upper vortex...and so I believe Gaston can catch up to my prior intensity forecast later on. By 48 to 96 hours...I show rapid intensification into a major category 3 then 4 hurricane as Gaston reaches favorable divergence on the northeast side of the upper vortex...which combined with increasingly warmer 29 to 30 deg C water temps (as noted in the above thermodynamic outlook) and warm core upper anticyclonic outflow of the storm will make conditions extremly favorable for intensification. I show a bit of weakening by 120 hours after Gaston lifts northward away from the 29 to 30 deg C water temp maximum on the current forecast track.

Impact Forecast...Impact swath shows gradual growth of the tropical storm wind field along the forecast track in anticipation of Gaston significantly strengthening over the next five days.

2016 Atlantic Hurricane Season Birdseye Discussion #96

By: NCHurricane2009, 4:12 AM GMT on August 24, 2016

...WEDNESDAY AUGUST 24 2016 12:15 AM EDT...
Although Fiona dissipates while moving into the western Atlantic...the remnants will encounter more favorable conditions in the next 24 hours...and then encounter more favorable conditions again after 48 hours...and thus could re-generate while drifting westward toward the southeastern United States over the next few days. See first special feature section below for additional details.

In the wake of Fiona...more serious tropical threats have emerged in the Atlantic with Tropical Storm Gaston at risk of strengthening into a major hurricane while moving into the central Atlantic...and interests in the northeastern Caribbean sea Islands...Bahamas...south Florida...and Gulf of Mexico should carefully monitor the progress of tropical wave Invest 99-L in the central tropical Atlantic as there is large uncertainty in the future strength of this system as it moves across these areas over the next five days. See second special feature section below for more information on Invest 99-L...and third special feature section below for more information on Tropical Storm Gaston. Visit www.nhc.noaa.gov for up to the minute latest information on Gaston.

Also see the following statement for one other area of interest...

The following statement concerns area of interest #3 marked over the eastern tropical Atlantic in the atmospheric features chart below. The vigorous tropical wave immediately behind Tropical Storm Gaston has become less organized while Gaston steals the low-level inflow needed for this tropical wave to further develop. Therefore no development is expected here and this is my final statement on this blog regarding this area of interest.

...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...REMNANT LOW OF FIONA...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...Fiona remains under westerly vertical shear due to upper vorticity in the western Atlantic (marked by blue-dashed line over Fiona in the above atmospheric featuers chart). Latest satellite shows Fiona as a cloud swirl with the occasional pockets of sheared-off thunderstorms...but the cloud swirl is fading as Fiona continues to weaken and thus it has been downgraded to a remnant low. As of 0000Z satellite imagery suggested the center of Fiona was located at 27N-67W. This is slightly west of the previous forecast and once again a westward adjustment is made to the lastest track forecast.

Atmospheric Outlook for the Forecast Period...Shortly Fiona's track will bend more westward due to the 1027 mb ridge currently entering the western Atlantic from the eastern United States. Initially it was thought the 1002 mb frontal cyclone currently moving into south-central Canada and the north-central US would bend the track northward again just after 72 hours...but now it appears it will not be strong enough to do this and instead Fiona (or anything left of it) is likely to drift westward toward the southeastern United States while trapped between the aforementioned 1027 mb ridge and the ridge to follow behind the 1002 mb frontal cyclone. In the next 24 hours...Fiona will slide under a more favorable atmospheric environment of upper anticyclonic flow with low shear and good outflow supplied by the upper ridge currenlty centered near Bermuda (marked by blue H just north of Fiona in the above atmospheric features chart) and my current forecast assumes Fiona could regenerate as a short-lived tropical depression in this environment. But by 48 hours Fiona will have to deal with another burst of westerly vertical shear delivered by the southern fracture of the upper trough that just entered the northwestern Atlantic (the fracture is marked by a small blue-dashed line to the northwest of Fiona). This is when I end my current forecast as I assume Fiona will have been too beaten up to re-generate after that time. But it should be noted that the favorable upper anticyclone currently over the southeastern US will spread into the western Atlantic behind the upper trough fracture...and if the remnants of Fiona are still intact enough it would have to be watched for re-genesis offshore of the eastern US coast after the 48 hour timeframe.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will cross over highly favorable 30 to 31 deg C waters. Thus thermodynamic conditions are not expected to be a problem for Fiona should she decide to re-generate.

24 Hr Forecast (0000Z Aug 25)...30 mph maximum sustained wind tropical depression centered southwest of Bermuda at 29N-70W

48 Hr Forecast (0000Z Aug 26)...Remnant low centered at 31N-72W

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 99-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...Showers and thunderstorms have continued to increasing in coverage and organization around the broad low pressure center of tropical wave Invest 99-L in the central tropical Atlantic within the last 24 hours. In fact the latest satellite organization suggests a tropical depression or tropical storm may be forming. Based on satellite animation...the broad tropical low was centered at 16N-58.8W as of 0000Z. Regardless of tropical cyclone formation or not...vigorous weather (gusty winds with heavy rainfall...with possible flash flooding risk) will overspread the Lesser Antilles...Virgin Islands...and Puerto Rico in the next 24 hours.

Atmospheric Outlook for the Forecast Period...The low pressure field of Fiona's remnants and divergence on the east side of the upper trough fracture currently east of North Carolina are expected to create a low-level ridge weakness that will cause this tropical wave to generally bend northward in track such that it moves across the northeastern Caribbean islands...Bahamas...and toward south Florida and Gulf of Mexico over the next few days. I have upped the short-term intensity forecast based on the improved satellite appearance and the fact it is currently in a favorable low shear/enhanced upper outflow environment beneath a favorable upper anticyclone (marked by blue H above Invest 99-L in the above atmospheric features chart). However I have not yet raised the intensity forecast for the later part of the forecast period for a myriad of reasons. First after 24 hours...land interaction with the Dominican Republic...the dry air mentioned in the thermodynamic outlook section below...and western Atlantic upper vorticity (marked by blue-dashed line northwest of 99-L) could have a negative influence on 99-L. At the end of the forecast period...one of two scenarios are possible. One is that this system establishes a small and highly favorable upper anticyclone between the south side of the upper trough east of North Carolina and east side of the upper trough currenlty over the Yucatan...in which case significant strengthening is possible. Or alternatively the upper trough east of North Carolina and Yucatan upper trough link up...preventing this system from establishing an upper anticyclone and ultimately suppressing this system.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 30 to 31 deg C waters during the forecast period. However dry saharan air to the west...seen in the above thermodynamics chart...could become a factor that limits strengthening.

24 Hr Forecast (0000Z Aug 25)...45 mph maximum sustained wind tropical stormapproaching Puerto Rico centered at 17N-64W

48 Hr Forecast (0000Z Aug 26)...35 mph maximum sustained wind tropical depression centered just north of the Dominican Republic centered at 20N-70W

72 Hr Forecast (0000Z Aug 27)...35 mph maximum sustained wind tropical depression over the southeastern Bahamas centered at 22N-74W

96 Hr Forecast (0000Z Aug 28)...45 mph maximum sustained wind tropical storm centered between the Bahamas and south Florida at 24N-79W

120 Hr Forecast (0000Z Aug 29)...45 mph maximum sustained wind tropical storm centered over the eastern Gulf of Mexico at 26N-84W

...SPECIAL FEATURE...TROPICAL STORM GASTON...
Current Prognosis...As expected Gaston has been steadily and briskly and intensifying...reaching 65 mph maximum sustained winds and soon to become a hurricane. As of 0000Z Gaston was moving into the central tropical Atlantic while centered at 14N-36.5W and has the classic satellite apperance of a tropical storm poised for strengthening with a circular core of spiral thunderstorm bands.

Atmospheric Outlook for the Forecast Period...The 1027 mb ridge currently over the north-central Atlantic is expected to steer this system westward across the central Atlantic ocean for the first 96 hours of the forecast period. The base of the upper trough currently in the northeastern Atlantic has left behind a cut-off upper vortex (marked by blue L to the northwest of Gaston in the above atmospheric features chart). Gaston is expected to strengthen into a hurricane strong and tall enough to feel the steering influence of this upper vortex...thus the 24 to 72 hour portion of the forecast shows a jump to the north while pulled into the east side of the upper vortex. Some less favorable southerly vertical shear imparted by the east side of the upper vortex may slow the strengthening rate of this system during this timeframe. By 96 hours...Gaston will have reached the north side of the upper vortex...which combined with the south side of the Atlantic surface ridge will cause Gaston to swing back to a more westward track. By 120 hours...Gaston is expected to bend northward in track and pass east of Bermuda while it begins to get pulled into a ridge weakness associated with the 1002 mb frontal cyclone currenlty over south-central Canada/north-central US as this frontal cyclone moves and strengthens across the north Atlantic.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters on the current forecast track...reaching more favorable 29 to 30 deg C waters by 96 to 120 hours. Lastest water vapor imagery shows Gaston's moisture field is warding off the patch of dry saharan air to its west and thus dry air is not expected to be a problem for Gaston.


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

24 Hr Forecast (0000Z Aug 25)...85 mph maximum sustained wind hurricane centered at 16N-44W

48 Hr Forecast (0000Z Aug 26)...105 mph maximum sustained wind hurricane centered at 20N-48W

72 Hr Forecast (0000Z Aug 27)...105 mph maximum sustained wind hurricane centered at 25N-52W

96 Hr Forecast (0000Z Aug 28)...130 mph maximum sustained wind hurricane centered at 27N-55W

120 Hr Forecast (0000Z Aug 29)...140 mph maximum sustained wind hurricane centered at 31N-56W

Track Forecast...Gaston's 0000Z position in the above current prognosis is essentially following my previous track forecast and therefore I have made no changes to my track forecast. See above atmospheric outlook section for details on the expected undulations in Gaston's forecast track.

Intensity Forecast...Gaston is slighlty stronger than my previous forecast and therefore my updated intensity forecast is slightly upped. By 96 to 120 hours...I show rapid intensification into a major category 3 then 4 hurricane as Gaston reaches favorable divergence on the northeast side of the upper vortex...which combined with increasingly warmer water temps (as noted in the above thermodynamic outlook) and warm core upper anticyclonic outflow of the storm will make conditions extremly favorable for intensification.

Impact Forecast...Impact swath shows gradual growth of the tropical storm wind field along the forecast track in anticipation of Gaston significantly strengthening over the next five days.

2016 Atlantic Hurricane Season Birdseye Discussion #95

By: NCHurricane2009, 4:13 AM GMT on August 23, 2016

...TUESDAY AUGUST 23 2016 12:15 AM EDT...
As Fiona weakens to a tropical depression while moving into the western Atlantic...more serious tropical threats emerge in the Atlantic with vigorous tropical wave Invest 90-L in the eastern tropical Atlantic strengthening into Tropical Storm Gaston and at risk of strengthening into a major hurricane...and interests in the northeastern Caribbean sea Islands...Bahamas...south Florida...and Gulf of Mexico should carefully monitor the progress of tropical wave Invest 99-L in the central tropical Atlantic as there is large uncertainty in the future strength of this system as it moves across these areas over the next five days. See first special feature section below for more information on Fiona...second special feature section below for more information on Invest 99-L...and third special feature section below for more information on Tropical Storm Gaston. Visit www.nhc.noaa.gov for up to the minute latest information on Fiona and Gaston.

Also see the following statements for one other area of interest...

The following statement concerns area of interest #2 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. Yet another vigorous tropical wave is emerging into the eastern tropical Atlantic immediately behind Tropical Storm Gaston. However this tropical wave is not expected to develop as Gaston signficiantly strengthens and steals the low-level inflow needed for this tropical wave to further develop.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1924Z-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 FIONA...
Current Prognosis...Fiona remains under westerly vertical shear due to upper vorticity in the western Atlantic (marked by blue-dashed line to the left of Fiona in the above atmospheric featuers chart). Latest nighttime infrared satellite shows Fiona as a cloud swirl with only a couple of small pockets of sheared-off thunderstorms and thus it is quiet conceivable that Fiona could dissipate into a remnant low in the near-term. As of 0000Z satellite imagery suggested the center of Fiona was located at 25N-61.5W.

Atmospheric Outlook for the Forecast Period...Fiona is expected to curve more northward in track shortly as the 1005 mb frontal depression currently moving into the northwestern Atlantic from the northeastern US is creating a ridge weakness. By 48 to 72 hours the track will bend more westward as the 1023 mb ridge currently over the eastern US moves offshore into the Atlantic and steers Fiona. Then at 96 hours the frontal cyclone currently over western Canada will move into the northwestern Atlantic which will likely pull Fiona northward in track. At 48 hours Fiona will reach a more favorable atmospheric environment of upper anticyclonic flow with low shear and good outflow supplied by the upper ridge offshore of the southeastern US. At 72 to 96 hours Fiona will be dealing with the southern fracture of of the upper trough currently supporting the 1005 mb frontal depression currently entering the northwestern Atlantic. Based on the lastest upper-level wind forecasts in the computer models...and because of the westward adjustment in the forecast track noted in the forecast track section below...Fiona at 96 hours will track northward straight into instead of east of this upper trough fracture which will create burst of westerly and northerly vertical shear likely to finally kill of Fiona. Just after the forecast period...Fiona will once again be in a lighter shear enviornment to the north of the upper trough fracture...so it remains to be seen if there is enough left of this tropical cyclone for any re-genesis offshore of the east US coast.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will cross over highly favorable 30 to 31 deg C waters.


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

24 Hr Forecast (0000Z Aug 24)...Remnant low south of Bermuda centered at 27.6N-65W

48 Hr Forecast (0000Z Aug 25)...40 mph maximum sustained wind tropical storm centered southwest of Bermuda at 29.2N-68.5W

72 Hr Forecast (0000Z Aug 26)...30 mph maximum sustained wind tropical depression centered west-southwest of Bermuda at 31N-70W

96 Hr Forecast (0000Z Aug 27)...Remnant low centered northwest of Bermuda at 34N-70W

Track Forecast...My updated forecast track is adjusted slightly westward when compared to the previous because Fiona passed west of instead of over 25N-60W earlier this past afternoon.

Intensity Forecast...I have once again slightly lowered the overall intensity forecast based on the currently-poor satellite appearance of Fiona. My current intensity forecast assumes Fiona will soon dissipate but then re-generate by 48 hours as Fiona reaches more favorable upper anticyclonic flow with lower shear and upper outflow per the above atmospheric outlook section...then dissipation again by 96 hours as Fiona deals with another burst of shear from a southern fracture upper trough.

Impact Forecast...I only show a small impact swath of tropical storm force winds around 48 hours based on my latest intensity forecast.

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 99-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...Showers and thunderstorms have been increasing in coverage and organization around the broad low pressure center of tropical wave Invest 99-L in the central tropical Atlantic within the last 24 hours. Based on satellite animation...the broad tropical low was centered at 15N-53.8W as of 0000Z. Satellite animation suggests a 1.3-W per 6 hour (or 5.2-W per 24 hour) motion because it was at 52.5W as of 1800Z. The early part of my forecast track listed below is based on this westward pace.

Atmospheric Outlook for the Forecast Period...The low pressure field of Fiona and divergence on the east side of the upper trough currently entering the Atlantic from the eastern US are expecte to create a low-level ridge weakness that will cause this tropical wave to generally bend northward in track such that it moves across the northeastern Caribbean islands...Bahamas...and toward south Florida and Gulf of Mexico over the next few days. I currently assume this system will strengthen into a tropical depression while moving across the northeastern Caribbean Sea Islands over the next 48 hours under a favorable upper anticyclone currently centered just north of the Lesser Antilles (marked by blue H to the left of Invest 99-L in the above atmospheric features chart). However just after that time I assume land interaction with the Dominican Republic...the dry air mentioned in the thermodynamic outlook section below...and western Atlantic upper vorticity currently shearing Fiona will likely cause this system to remain weak through 72 hours. After that time the intensity forecast becomes highly uncertain. If this system establishes a small and highly favorable upper anticyclone between the south side of the upper trough currently entering the Atlantic from the eastern US and east side of the upper vortex currently over the northern Yucatan....then it could significantly strengthen while moving across the Bahamas...south Florida...and into the Gulf of Mexico. However if the south side of the upper trough and Yucatan upper vortex link up...then a barrier of unfavorable wind shear could cause this system to struggle through 120 hours. My current intensity forecast splits the difference between both solutions and shows only slow strengthening into a weak tropical storm by 120 hours.

Thermodynamic Outlook for the Forecast Period...This system will be crossing over highly favorable 29 to 31 deg C waters during the forecast period. However dry saharan air to the west...seen in the above thermodynamics chart...could become a factor that limits strengthening.

24 Hr Forecast (0000Z Aug 24)...Tropical low crossing the Lesser Antilles centered at 15N-59W

48 Hr Forecast (0000Z Aug 25)...35 mph maximum sustained wind tropical depression approaching Puerto Rico centered at 17N-64W

72 Hr Forecast (0000Z Aug 26)...Remnant low centered just north of the Dominican Republic centered at 20N-70W

96 Hr Forecast (0000Z Aug 27)...35 mph maximum sustained wind tropical depression over the southeastern Bahamas centered at 22N-74W

120 Hr Forecast (0000Z Aug 28)...45 mph maximum sustained wind tropical storm centered between the Bahamas and south Florida at 24N-79W

...SPECIAL FEATURE...TROPICAL STORM GASTON...
Current Prognosis...The strong and organized tropical wave in the eastern tropical Atlantic strengthened into the seventh tropical depression of the season...and then the seventh tropical storm of the season...within the last 24 hours. As such this tropical cyclone is now named Gaston. As of 0000Z newly-named Gaston was centered southwest of the Republic of Cabo Verde at 12.5N-30W and has the classic satellite apperance of a tropical storm poised for strengthening with spiral thunderstorm bands in all quadrants of the circulation.

Atmospheric Outlook for the Forecast Period...Computer models suggest the favorable anticyclonic upper ridging currently over Gaston will expand westward as Gaston moves across the Atlantic. Thus wind shear is expected to remain favorably low and upper outflow expected to remain favorably high through most of the forecast period. The 1028 mb ridge currently over the Atlantic is expected to steer this system westward across the eastern and central Atlantic ocean. The base of the upper trough currently moving into the northeastern Atlantic has left behind a cut-off upper trough which will soon close off into an upper vortex. The current forecast assumes Gaston strengthens into a hurricane strong and tall enough to feel the steering influence of this upper vortex...thus the 48 to 96 hour portion of the forecast shows a jump to the north while pulled into the east side of the upper vortex. Some less favorable southerly vertical shear imparted by the east side of the upper vortex may slow the strengthening rate of this system during this timeframe. However by 120 hours...Gaston will have reached the north side of the upper vortex...which combined with the south side of the Atlantic surface ridge will cause Gaston to swing back to a more westward track.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters on the current forecast track...reaching more favorable 29 deg C waters by 120 hours. The dry saharan air in the eastern and central tropical Atlantic appears to have been reduced by Fiona and tropical wave Invest 99-L to the west...which in addition to the moisture field of Gaston should make dry air unlikely to adversely affect Gaston.


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

24 Hr Forecast (0000Z Aug 24)...60 mph maximum sustained wind tropical storm centered at 14.5N-37W

48 Hr Forecast (0000Z Aug 25)...80 mph maximum sustained wind hurricane centered at 16N-44W

72 Hr Forecast (0000Z Aug 26)...100 mph maximum sustained wind hurricane centered at 20N-48W

96 Hr Forecast (0000Z Aug 27)...100 mph maximum sustained wind hurricane centered at 25N-52W

120 Hr Forecast (0000Z Aug 28)...125 mph maximum sustained wind hurricane centered at 27N-55W

Track Forecast...My updated track forecast is an overall west shift compared to the previous because Gaston has consolidated into a tropical cyclone further west than I previously forecasted.

Intensity Forecast...Gaston is currently stronger than I previously anticipated it would be by this time and therefore the first part of the forecast is higher than my previous. However the 96 hour timeframe for my forecast is a little less than previous because the more westward position of the tropical cyclone (per the above track forecast section) is likely to cause Gaston to be closer to the cut-off upper vortex developing in the central Atlantic...which will cause more in the way of unfavorable southerly vertical shear when Gaston interacts with the upper vortex. At 120 hours...I show rapid intensification into a major category 3 hurricane as Gaston reaches divergence on the northeast side of the upper vortex...which combined with increasingly warmer water temps (as noted in the above thermodynamic outlook) and warm core upper anticyclonic outflow of the storm will make conditions extremely favorable for intensification.

Impact Forecast...Impact swath shows gradual growth of the tropical storm wind field along the forecast track in anticipation of Gaston significantly strengthening over the next five days.

2016 Atlantic Hurricane Season Birdseye Discussion #94

By: NCHurricane2009, 3:16 AM GMT on August 22, 2016

...SUNDAY AUGUST 21 2016 11:20 PM EDT...
Tropical Storm Fiona expected to continue west-northwestard across the Atlantic Ocean and is expected to pass south and west of Bermuda. See first special feature section below for additional details and visit www.nhc.noaa.gov for up to the minute latest information on Fiona.

Also see the following statements for two other areas of interest...including the tropical wave which has just emerged from western Africa and could become a strong hurricane while moving across the eastern and central Atlantic...

The following statement concerns area of interest #1 marked over the central tropical Atlantic in the atmospheric features chart below. Tropical wave Invest 99-L has once again lost thunderstorm activity while battling dry saharan air. Fiona is expected to create a low-level ridge weakness that will generally cause the track of this tropical wave to bend more northward in track and pass over or near the northeastern Caribbean Sea Islands and perhaps the Bahamas over the next few days. The dry air...potential burst of northerly shear in the near-term as the north-central Atlantic upper trough deposits a southward-digging cut-off upper vortex...the lingering upper vorticity in the western Atlantic...and the potential for shear delivered by a forecast southern fracture of the upper trough currently over the eastern US all create uncertainty in whether or not tropical wave Invest 99-L will develop or not...and therefore I have dropped it as a special feature on this blog at this time. The only favorable factor for development will be a low shear and good upper outflow environment provided by the upper anticyclone which has recently moved offshore of the southeastern US and is currently centered near the Carolina coast...and therefore interests in the northeastern Caribbean Sea Islands and Bahamas should continue to monitor the progress of this tropical wave as it moves into the area.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. The tropical wave that was over western Africa remains organized as a tropical low pressure spin as it enters the eastern tropical Atlantic to the southeast of the Republic of Cabo Verde and thus has been upgraded to Invest 90-L. See second special feature section below for additional details. It is possible that this system strengthens into a strong hurricane while moving across the eastern and central Atlantic over the next few days...stay tuned.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1929Z-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 FIONA...
Current Prognosis...Fiona remains under westerly vertical shear due to upper vorticity to the northeast (marked by blue-dashed line northeast of Fiona in the above atmospheric features chart) and will soon be dealing with westerly vertical shear from upper vorticity in the western Atlantic (marked by blue-dashed line to the northwest in the above atmospheric featuers chart). Despite intensifying to a peak of 50 mph maximum sustained winds during last night's thunderstorm burst...I did not issue a special update to up the near-term intensity forecast as I expected the westerly vertical shear to weaken it back to minimal tropical storm strength and indeed this has occurred. In fact the thunderstorm bursts are less impressive than twenty-four hours ago and thus it looks like Fiona may even weaken to tropical depression strength or even dissipate. As of 1800Z this past afternoon satellite imagery suggested the center of Fiona was located at 24N-54W.

Atmospheric Outlook for the Forecast Period...While diving southeast into the Atlantic...the surface ridge that was offshore of eastern Canada has intensified to 1029 mb which in turn has caused Fiona to bend more westward in track. A bend back towards the north is likely at 24 to 48 hours as the 1007 mb frontal depression currently over the northeastern US dives into the northwestern Atlantic and creates a ridge weakness. By 72 to 96 hours the track will bend more westward as the 1019 mb ridge currently over the central US moves offshore into the Atlantic and steers Fiona. Then at 120 hours the frontal cyclone currently over western Canada will move into the northwestern Atlantic which will likely pull Fiona northward in track. Although Fiona will be dealing with westerly vertical shear from upper vorticity as noted in the above current prognosis...this upper vorticity will be continuously weakening during the forecast period which may allow Fiona to survive. If Fiona survives...at 72 hours she will be rewarded by a favorable environment of upper anticyclonic flow with low shear and good outflow supplied by the upper ridge offshore of the Carolinas which has recently left the southeastern US. At 96 to 120 hours Fiona will be dealing with the southern fracture of of the upper trough currently supporting the 1007 mb northeastern US frontal depression...with this fracture inducing a burst of westerly shear at first...with the shear potentially reducing as it amplifies into a cut-off upper vortex while Fiona bends northward in track and aligns with the direction of the upper-level winds on the east side of such an upper vortex. Its also possible upper divergence on the east side of the fracture aids Fiona during this time.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will cross over highly favorable 30 to 31 deg C waters.


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

24 Hr Forecast (1800Z Aug 22)...35 mph maximum sustained wind tropical depression centered at 25N-60W

48 Hr Forecast (1800Z Aug 23)...35 mph maximum sustained wind tropical depressioncentered at 27.5N-62.5W

72 Hr Forecast (1800Z Aug 24)...45 mph maximum sustained wind tropical storm centered just south-southwest of Bermuda at 29N-66W

96 Hr Forecast (1800Z Aug 25)...35 mph maximum sustained wind tropical depression centered just west-southwest of Bermuda at 30.5N-69W

120 Hr Forecast (1800Z Aug 26)...40 mph maximum sustaiend wind tropical storm centered northwest of Bermuda at 34N-69W

Track Forecast...Based on the 1800Z center fix in the current prognosis Fiona is a bit northwest of the previous forecast track and therefore my updated forecast points are adjusted north and west accordingly.

Intensity Forecast...I have slightly lowered the overall intensity forecast based on the currently-poor satellite appearance of Fiona. However my current intensity forecast still assumes Fiona survives the current bout of westerly vertical shear as the upper vorticity inducing the shear will be continuously weakening...and because Fiona will be over rather warm water temps as mentioned in the above thermodynamic outlook to the degree that these waters induce enough instability for Fiona to continue to fire bursts of thunderstorms. I show some strenghening at 72 hours as Fiona reaches more favorable upper anticyclonic flow with lower shear and upper outflow per the above atmospheric outlook section...then some weakening at 96 hours as Fiona deals with another burst of shear from a southern fracture upper trough...but then some strengthening again at 120 hours as Fiona begins to have a more favorable interaction with this upper trough.

Impact Forecast...My impact swath of tropical storm force winds in the above forecast graphic is the extrapolation of the 5 PM EDT NHC wind field along my forecast track. The swath is absent along the forecast track where Fiona is expected to be a tropical depression in my latest intensity forecast.

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE INVEST 90-L...
This special feature section is for area of interest #2 marked in the above atmospheric features chart.

Current Prognosis...The strong and organized tropical wave that was over western Africa is now in the eastern tropical Atlantic to the southeast of the Republic of Cabo Verde with its low pressure spin centered at 11N-21W as of 1800Z. This is essentially in agreement with my previous track forecast and therefore my updated track forecast listed below is essentially an extension of the previous. The tropical wave continues to present itself as a low pressure spin with spiral bands wrapped around. However it is not quiet as organized as I expected it would be by now as there is not yet a central dense overcast of thunderstorms over the center of low pressure. Therefore I have lowered my overall intensity forecast.

Atmospheric Outlook for the Forecast Period...Computer models suggest the favorable anticyclonic upper ridging currently over the tropical wave will expand westward as the tropical wave moves across the Atlantic. Thus wind shear is expected to remain favorably low and upper outflow expected to remain favorably high through most of the forecast period. The 1029 mb ridge currently over the Atlantic is expected to steer this system westward across the eastern and central tropical Atlantic. The base of the upper trough currently in the north-central Atlantic is expected to cut-off into an upper vortex...and the current forecast assumes this system strengthens into a hurricane strong and tall enough to feel the steering influence of this upper vortex...thus the later part of the track forecast shows a jump to the north while pulled into the east side of the upper vortex. Some less favorable southerly vertical shear imparted by the east side of the upper vortex may slow the strengthening rate of this system at the end of the forecast period.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters on the forecast track listed below. The dry saharan air in the eastern and central tropical Atlantic appears to have been reduced by Fiona and tropical wave Invest 99-L to the west...which in addition to the moisture field of this tropical wave help makes it likely that this tropical wave will develop.

24 Hr Forecast (1800Z Aug 22)...Organized tropical low centered southwest of the Republic of Cabo Verde at 12N-26W

48 Hr Forecast (1800Z Aug 23)...45 mph maximum sustained wind tropical storm centered at 13.5N-33W

72 Hr Forecast (1800Z Aug 24)...70 mph maximum sustained wind tropical storm centered at 15N-40W

96 Hr Forecast (1800Z Aug 25)...95 mph maximum sustained wind hurricane centered at 18.5N-46W

120 Hr Forecast (1800Z Aug 26)...105 mph maximum sustained wind hurricane centered at 22N-48.5W

2016 Atlantic Hurricane Season Birdseye Discussion #93

By: NCHurricane2009, 4:01 AM GMT on August 21, 2016

...SUNDAY AUGUST 21 2016 12:02 AM EDT...
Tropical Storm Fiona expected to continue west-northwestard across the Atlantic Ocean and now is expected to pass south and southwest of Bermuda. See first special feature section below for additional details and visit www.nhc.noaa.gov for up to the minute latest information on Fiona.

Also see the following statements for three other areas of interest...

The following statement concerns area of interest #1 marked over the central tropical Atlantic in the atmospheric features chart below. Tropical wave Invest 99-L has become less organized but could still develop while moving into the eastern Caribbean region. Therefore the islands in the eastern Caribbean should continue to monitor the progress of this tropical wave. See second special feature section below for additional details.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. The tropical wave that was over southwestern Mali has rapidly intensified and developed an organizing tropical low pressure spin since the previous update and therefore I have upgraded it to a special feature on this blog with a tropical cyclone formation forecast. See third special feature section below for additional details. Based on the current position of the newly-formed tropical low pressure spin...it appears most of the weather will pass south of the Republic of Cabo Verde...but a northern band of squally weather overspreading the area cannot be ruled out. It is also possible that this system strengthens into a strong hurricane while moving across the eastern and central tropical Atlantic over the next few days.

The following statement concerns area of interest #3 marked in the western Atlantic to the south of Bermuda in the atmospheric features chart below. The surface trough and thunderstorm activity in this area has dissipated due to suppression from the elongated upper vorticity extending across the southern Gulf of Mexico and western Atlantic which shifted southward over the disturbance. This is my final statement on this area of interest.

...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...TROPICAL STORM FIONA...
Current Prognosis...As expected...Fiona has traveled north enough to encounter westerly vertical shear while reaching cut-off upper vorticity that has been north of the storm over the last few days. In the face of this unfavorable shear...so far Fiona has held on to minimal tropical storm strength while firing bursts of thunderstorms over and east of the center. As of 1800Z this past afternoon satellite imagery suggested the center of Fiona was located at 20.9N-48.5W.

Atmospheric Outlook for the Forecast Period...The frontal cyclone that has recently moved into Europe...and intensifying 993 mb frontal cyclone currently over the north-central Atlantic...have weakened the Atlantic surface ridge which explains the northward component of the westward track over the last few days. However in the next 24 hours...both frontal cyclones will move eastward and away while the 1021 mb ridge just offshore of eastern Canada is expected to intensify...which will cause the track to bend more westward. A bend back towards the north is then likely at 48 to 72 hours as the vigorous 999 mb frontal cyclone currently over the north-central US dives into the western Atlantic and creates another ridge weakness. Because Fiona has tracked more south and west than the previous forecasts (per the forecast track section below)...it is now clear Fiona will not turn northward out to sea in this ridge weakness...and instead Fiona by 96 to 120 hours will bend more westward in track again as the 1022 mb ridge currently over the western US moves offshore into the Atlantic and steers it. Fiona will be dealing with breaking up upper vorticity to its north (marked by a pair of blue-dashed lines to the north and northeast of the storm in the above atmospheric features chart) and to its northwest extending from the southern Gulf of Mexico and into the western Atlantic (also marked by a blue-dashed line). Afterwards by 96 hours Fiona will be rewarded by a favorable environment of upper anticyclonic flow with low shear and good outflow supplied by the southeastern US upper ridge which is expanding into the western Atlantic. Then by 120 hours Fiona again will deal with less favorable shear delivered by what will be a southern fracture of the upper trough currently supporting the central US 999 mb frontal cyclone.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will cross over highly favorable 29 to 30 deg C waters.


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

24 Hr Forecast (1800Z Aug 21)...40 mph maximum sustained wind tropical storm centered at 22.5N-53W

48 Hr Forecast (1800Z Aug 22)...40 mph maximum sustained wind tropical storm centered at 24N-59W

72 Hr Forecast (1800Z Aug 23)...40 mph maximum sustained wind tropical storm centered at 27N-61W

96 Hr Forecast (1800Z Aug 24)...50 mph maximum sustained wind tropical storm centered just south of Bermuda at 29N-65W

120 Hr Forecast (1800Z Aug 25)...45 mph maximum sustained wind tropical storm centered just southwest of Bermuda at 30.5N-68W

Track Forecast...Based on the 1800Z center fix in the current prognosis I estimate Fiona is about 1.5 latitude degrees south and 1.5 longitude degrees west of my previous forecast. Therefore Fiona will be too far south to recurve northward out to sea by the ridge weakness to be created by the 999 mb frontal cyclone currently over the north-central US. This has resulted in a notable south and westward adjustment in the forecast track.

Intensity Forecast...Even though Fiona is under westerly vertical shear...I currently forecast Fiona to survive as the upper vorticity producing the shear is going to be breaking up per the above atmospheric outlook section...and the rather warm water temps mentioned in the above thermodynamic outlook section may induce enough instability for Fiona to continue to fire bursts of thunderstorms. I show some strenghening at 96 hours as Fiona reaches more favorable upper anticyclonic flow with lower shear and upper outflow...then some weakening at 120 hours as Fiona once again encounters some shear as noted at the end of the above atmospheric outlook section.

Impact Forecast...My impact swath of tropical storm force winds in the above forecast graphic is the extrapolation of the 5 PM EDT NHC wind field along my forecast track.

...SPECIAL FEATURE...CENTRAL ATLANTIC TROPICAL WAVE INVEST 99-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...Since the previous update...the thunderstorm activity of this tropical wave has reduced...become less organized...and the low pressure spin has become larger and broader. It appears this is due to the dry saharan air that is in the eastern and central tropical Atlantic. However in the last few hours there has been some increase in the thunderstorm activity...but this activity remains lopsided to the west of the low pressure center due to northeasterly vertical shear induced by the southeastern periphery of an upper anticyclone in the central tropical Atlantic (marked by blue H to the north of Invest 99-L in the above atmospheric features chart). As of 1800Z...it appears the center of the broad low pressure spin was at 10N-38.6W which is essentially along the previous forecast track. Therefore I have not made any changes to the forecast track.

Atmospheric Outlook for the Forecast Period...In addition to the less organized apperance noted in the current prognosis...another reason I delay tropical cyclone formation in the updated forecast is due to the possiblity of the northeasterly vertical shear mentioned in the above current prognosis lasting longer as the lastest model runs show a more amplified cut-off developing from the upper trough currently in the north-central Atlantic. It isn't until 72 hours until this tropical wave escapes the southwest side of the amplified cut-off and becomes tucked under the south side of upper anticyclonic flow with lower shear and more upper outflow...and this is when I currently forecast tropical cyclone formation. While this tropical wave moves into the Caribbean...what's left of the upper vorticity over the southern Gulf and western Atlantic will dive southward toward the Caribbean while pushed by upper riding expanding into the western Atlantic from the southeastern US. Uncertainty about the influence of this upper vorticity is why I slow only light strengthening at the end of the forecast period. On a final note...the track of this system is likely to bend more northward toward the islands of the northeastern Caribbean (Puerto Rico and Hispaniola) at the end of the forecast period while experiencing a ridge weakness induced by Tropical Storm Fiona which will be due north of this system if the current forecasts hold.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will be over rather favorable 28 to 30 deg C thru the entire forecast period. Water vapor imagery in the above thermodynamics chart shows this system is producing its own moisture field which has potential to ward off the dry saharan air in the central tropical Atlantic.

24 Hr Forecast (1800Z Aug 21)...Tropical low centered at 11.2N-44.5W

48 Hr Forecast (1800Z Aug 22)...Tropical low centered at 11.7N-49W

72 Hr Forecast (1800Z Aug 23)...35 mph maximum sustained wind tropical depression approaching the Lesser Antilles centered at 13.2N-54.5W

96 Hr Forecast (1800Z Aug 24)...45 mph maximum sustained wind tropical storm over the Lesser Antilles centered at 14N-60.5W

120 Hr Forecast (1800Z Aug 25)...45 mph maximum sustained wind tropical storm centered south of Puerto Rico at 16N-66W

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

Current Prognosis...The tropical wave that was over southwestern Mali has rapidly intensified and developed an organizing tropical low pressure spin since the previous update and therefore I have upgraded it to a special feature on this blog with a tropical cyclone formation forecast which is listed below. As of 1800Z satellite imagery suggested the center of this low pressure spin was entering the tropical Atlantic at 11N-15W. Twenty-four hours prior satellite suggested that the tropical wave over southwestern Mali at 10W longitude...suggesting a 5W longitude pace per 24 hours. However the forecast track listed below shows an increasingly faster westward pace to keep up with the lastest computer model runs. It appears the 1021 mb ridge offshore of eastern Canada will notably strengthen while spreading into the Atlantic which will cause the westward acceleration.

Atmospheric Outlook for the Forecast Period...Computer models suggest the favorable anticyclonic upper ridging currently over the tropical wave will expand westward as the tropical wave moves across the Atlantic. Thus wind shear is expected to remain favorably low and upper outflow expected to remain favorably high through the forecast period. The 1021 mb ridge offshore of eastern Canada will notably strengthen while spreading into the Atlantic which will cause this system to move west-northwest through the forecast period.

Thermodynamic Outlook for the Forecast Period...This system will be over favorable 27 to 28 deg C waters on the forecast track listed below. The dry saharan air in the eastern and central tropical Atlantic appears to have been reduced by Fiona and tropical wave Invest 99-L to the west...which in addition to the moisture field of this tropical wave help makes it likely that this tropical wave will develop.

24 Hr Forecast (1800Z Aug 21)...Organized tropical low southeast of the Republic of Cabo Verde centered at 11N-20W

48 Hr Forecast (1800Z Aug 22)...40 mph maximum sustained wind tropical storm centered southwest of the Republic of Cabo Verde at 12N-26W

72 Hr Forecast (1800Z Aug 23)...60 mph maximum sustained wind tropical storm centered at 13.5N-33W

96 Hr Forecast (1800Z Aug 24)...80 mph maximum sustained wind hurricane centered at 15N-40W

120 Hr Forecast (1800Z Aug 25)...100 mph maximum sustained wind hurricane centered at 17N-47W

2016 Atlantic Hurricane Season Birdseye Discussion #92

By: NCHurricane2009, 5:40 AM GMT on August 19, 2016

...FRIDAY AUGUST 19 2016 1:45 AM EDT...
Tropical Storm Fiona expected to continue northwestard and then northward across the central Atlantic ocean and stay east of Bermuda over the next few days. See first special feature section below for additional details and visit www.nhc.noaa.gov for up to the minute latest information on Fiona.

Also see the following statements for three other areas of interest potentially affecting Bermuda...the Republic of Cabo Verde...and eastern Caribbean region over the next few days...

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic in the atmospheric features chart below. The vigorous tropical wave that emerged from Africa yesterday has rapidly organized into tropical disturbance Invest 99-L at a location southwest of the Republic of Cabo Verde. As such tropical cyclone formation is becoming more likely as this system continues across the central tropical Atlantic and toward the Lesser Antilles and eastern Caribbean sea region. Therefore interests in these areas should carefully monitor this tropical wave over the next few days. See second special feature section below for additional details.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. Although the tropical wave over southern Mali has not become better organized or stronger...the European (ECMWF) computer model continues to forecast tropical cyclone formation with a more northerly solution such that the track passes over the Republic of Cabo Verde...and recently the GFS computer model has started to jump onboard with a similar solution. Therefore interests at the Republic of Cabo Verde should continue to monitor this tropical wave. I am not upgrading this tropical wave to a special feature with a tropical cyclone formation forecast unless it shows more thunderstorm activity or becomes better organized.

The following statement concerns area of interest #3 marked in the western Atlantic to the south of Bermuda in the atmospheric features chart below. An area of concentrated showers and thunderstorms featuring a surface trough persists due to split flow upper divergence between an upper vortex centered over the southeastern Gulf of Mexico and upper anticyclone centered north of the Caribbean. Recently this system has become a bit better organized as the favorable upper anticyclone has shifted a bit westward and become aligned with the thunderstorms. Over the next 72 hours...the aforementioned upper vortex is expected to break up and shift south as the upper ridging over the southeastern US expands into the western Atlantic. Yesterday the GFS model suggested the eastern part of the breaking upper vorticity would become a small upper vortex which would have allowed this disturbance to survive to the west of such a small upper vortex. However the most recent GFS suggests an east-west narrow upper trough shifting southward over the disturbance...which could suppress its upper outflow and produce a burst of unfavorable northerly shear. Additional uncertainty will be caused by Tropical Storm Fiona approaching from the southeast which could interefere with this system's low-level inflow needed for development. Should this system survives all of this in the next five days...any tropical cyclone that develops would likely move northward toward the vigorous frontal cyclone currently over central Canada which will arrive into the northwestern Atlantic region and therefore interests in Bermuda should monitor this area of disturbed weather.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1925Z-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 FIONA...
Current Prognosis...The ball of thunderstorms that formed over the center of Fiona last night has been expanding over the last 24 hours...and as a result the tropical storm has slightly strengthened. Fiona has another 24 hours to strengthen before conditions become less favorable per the atmospheric and thermodynamic outlook sections below. As of 0000Z...satellite imagery suggested the center of Fiona was located at 17N-41.5W.

Atmospheric Outlook for the Forecast Period...The intensifying 984 mb frontal cyclone in the northeastern Atlantic...and intensifying 999 mb frontal cyclone currently over the northwestern Atlantic...have weakened the Atlantic surface ridge which has caused Fiona to bend northward in its westward track. Behind both frontal cyclones...a strong Atlantic surface ridge is expected to re-develop which will cause the track to bend back westward by 72 hours. Toward the end of the 120-hour forecast period...a bend back towards the north is likely as the vigorous frontal cyclone currently over central Canada dives into the western Atlantic and creates another ridge weakness. Fiona remains embedded in large-scale upper anticyclonic flow which is keeping vertical shear favorably low and upper outflow favorably high. However some cut-off upper vorticity lingers to Fiona's north currently structured as an invereted upper trough and upper vortex marked by a blue-dashed line and blue L in the atmospheric features chart above. This upper vorticity will retrograde westward with Fiona in the upper anticyclonic flow...with Fiona reaching the unfavorable upper vorticity just after 24 hours due to the current north component in the storm track. This is why rapid weakening is shown after 24 hours. By 72 hours this upper vorticity is shown in model runs to break up and diminish which could allow this tropical cyclone to survive. At 96 hours what's left of the upper vorticity producing the tropical disturbance south of Bermuda (area of interest #3 in the above atmospheric features chart) will dive southward and diminish while the more favorable upper ridging currently over the southeastern US expands into the western Atlantic. At the 120 hour forecast position Fiona will reach this upper ridge upon which time some re-strengthening is possible.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will be over favorable 28 deg C waters during the early part of the forecast period...reaching even more favorable 29 to 30 deg C waters by the end of the forecast period. Latest water vapor imagery (seen in the above thermodynamics chart) suggests Fiona is producing its own moisture field strong enough to ward off the surrounding dry saharan air in the central tropical Atlantic. However after 24 hours as Fiona encounters westerly vertical shear from upper vorticity...the shear could waft in the unfavorable dry air which will aid in weakening the tropical storm during that timeframe.


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

24 Hr Forecast (0000Z Aug 20)...60 mph maximum sustained wind tropical storm centered at 20N-44W

48 Hr Forecast (0000Z Aug 21)...40 mph maximum sustained wind tropical storm centered at 23N-47.5W

72 Hr Forecast (0000Z Aug 22)...40 mph maximum sustained wind tropical storm centered at 23.5N-51.5W

96 Hr Forecast (0000Z Aug 23)...40 mph maximum sustained wind tropical storm centered at 26N-55W

120 Hr Forecast (0000Z Aug 24)...50 mph maximum sustained wind tropical storm centered at 29N-57.5W

Track Forecast...I have adjusted my track forecast slightly south of my previous to account for Fiona being slighlty south of the previous as of the 0000Z center fix.

Intensity Forecast...Fiona is once again weaker than than my previous forecast and so I have lowered my forecast peak intensity for 0000Z Aug 20 from 70 to 60 mph maximum sustained winds. This forecast peak is higher than the latest (11 PM EDT) forecast from the National Hurricane Center (NHC) as I believe the currently impressive nature of the thunderstorm canopy will allow for some decent strengthening. Weakening is shown afterwards due to the unfavorable atmospheric and thermodynamic conditions (outlined in the above outlook sections) in the 48 to 96 hour timeframe. Fiona is expected to reach more favorable upper ridging in the western Atlantic at the end of the 120-hour forecast period per the above atmospheric outlook section and therefore re-strengthening is shown at this time.

Impact Forecast...My impact swath of tropical storm force winds in the above forecast graphic is the extrapolation of the 11 PM EDT NHC wind field along my forecast track and is made proportional to the forecast strength of the tropical cyclone...made wider where the storm is forecast to reach peak strength...and later narrowed to reflect expected weakening at the end of the forecast period.

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE INVEST 99-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...The vigorous tropical wave that emerged from western Africa yesterday has rapidly produced an organizing tropical low pressure spin located at 10N-27.5W to the southwest of the Republic of Cabo Verde as of 0000Z. As a result this tropical wave is now upgraded to tropical disturbance Invest 99-L. Satellite imagery suggests this spin was developing around 24W longitude at 1200Z this past afternoon...indicating a completion of 3.5W longitude of travel per 12 hours (or 7W per 24 hours) when comparing the 1200Z and 0000Z fixes. As such my forecast track listed below is initially based on a 7W longitude per 24 hour rate...but I later slow this rate as to not stray too far west of the current computer model runs. All of the thunderstorm activity is currently lopsided to the west of the developing low pressure spin due to northeasterly vertical shear induced by the southeastern periphery of an upper anticyclone in the eastern tropical Atlantic (marked by blue H to the northwest of Invest 99-L in the above atmospheric features chart).

Atmospheric Outlook for the Forecast Period...The northeasterly vertical shear should reduce by 48 hours as the tropical wave leaves the southeastern periphery of the upper anticyclone mentioned in the above current prognosis and becomes tucked under the south side of the upper anticyclone. The favorable low shear and upper outflow of the upper anticyclonic flow will be favorable for development...and therefore tropical cyclone formation is likely as this tropical wave moves across the central tropical Atlantic and toward the Lesser Antilles and eastern Caribbean region. However while this system nears the Caribbean...what's left of the upper vorticity producing the tropical disturbance south of Bermuda (area of interest #3 in the above atmospheric features chart) will dive southward toward the Caribbean while pushed by upper riding expanding into the western Atlantic from the southeastern US. Uncertainty about the influence of this upper vorticity is why I slow the strengthening rate at the end of the 120-hour forecast period. On a final note...even though tropical storm Fiona to the northwest is expected to turn northward into a ridge weakness by the end of the 120-hour forecast period...this tropical wave will be too far south to feel this weakness and therefore will likely continue into the eastern Caribbean sea region just beyond the 120-hour forecast period.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will be over rather favorable 28 to 30 deg C thru the entire forecast period. Like Fiona...water vapor imagery in the above thermodynamics chart shows this system is producing its own moisture field that is likely capable of warding off what's left of the dry saharan air in the central tropical Atlantic.

24 Hr Forecast (0000Z Aug 20)...Tropical low centered at 10N-34.5W with thunderstorms sheared westward from the center

48 Hr Forecast (0000Z Aug 21)...Better organized tropical low centered at 11N-40W

72 Hr Forecast (0000Z Aug 22)...40 mph maximum sustained wind tropical storm centered at 11.5N-46W

96 Hr Forecast (0000Z Aug 23)...60 mph maximum sustained wind tropical storm centered at 12N-50W

120 Hr Forecast (0000Z Aug 24)...70 mph maximum sustained wind tropical storm approaching the Lesser Antilles centered at 13.5N-56W

2016 Atlantic Hurricane Season Birdseye Discussion #91

By: NCHurricane2009, 6:42 AM GMT on August 18, 2016

...THURSDAY AUGUST 18 2016 2:55 AM EDT...
Tropical depression six strengthens into Tropical Storm Fiona while moving into the central tropical Atlantic. See special feature section below for additional details on this new tropical storm and visit www.nhc.noaa.gov for up to the minute latest information.

Also see the following statements for three 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 suggests that the small tropical wave that recently emerged from western Africa is becoming absorbed by the larger more vigorous tropical waves mentioned in area of interest #2. Therefore this is the final statement on this feature on this blog.

The following statement concerns area of interest #2 marked over western Africa and eastern tropical Atlantic in the atmospheric features chart below. A large and vigorous tropical wave which was over western Africa 24 hours ago has moved into the eastern tropical Atlantic but its thunderstorms have weakened. Satellite imagery also suggests a second tropical wave is currently located over southern Mali. Computer model solutions continue to vary with both tropical waves. The 00Z CMC shows the wave currently in the eastern tropical Atlantic developing with a more southern solution (passing south of the Republic of Cabo Verde and developing toward the Lesser Antilles over the next few days). The 12Z Euro and 12Z NAVGEM shows the wave from southern Mali dominating with a more northward track passing over the Republic of Cabo Verde. The 00Z GFS shows no tropical cyclone formation from either wave. Waiting for more consistency in the model runs and any signs of organization from either tropical wave before considering an upgrade to a special feature on this blog with a tropical cyclone formation forecast. However interests over the Republic of Cabo Verde should monitor the progress of the tropical wave currently over southern Mali.

The following statement concerns area of interest #3 marked in the western Atlantic to the south of Bermuda in the atmospheric features chart below. An area of concentrated showers and thunderstorms featuring a surface trough has developed due to split flow upper divergence between an upper vortex centered over the Florida Straits and upper anticyclone centered north of the Lesser Antilles. Over the next 96 hours...this upper vortex is expected to split into two as the upper anticyclone centered over North Carolina moves offshore...with the possiblity of upper divergence between the west side of the eastern upper vortex and east side of the North Carolina upper anticyclone continuing this area of disturbed weather. If the favorable North Carolina upper anticyclone overspreads this area...tropical cyclone formation may become possible. Any tropical cyclone that develops in this region in the 96 hour timeframe is likely to move northward toward the vigorous frontal cyclone currenlty over western Canada which will arrive into the northwestern Atlantic region by that time and therefore interests in Bermuda should monitor this area of disturbed weather.

...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 FIONA...
Current Prognosis...Tropical depression six has strengthend into Tropical Storm Fiona in the last 24 hours while moving west-northwest into the central tropical Atlantic. Fiona has struggled while ingesting some of the dry saharan air that surrounds it...but in recent hours has devloped a ball of deep thunderstorms over the center that suggests survival and further strengthening is more likely. As of 0000Z...satellite imagery suggested the center of Fiona was located at 15.5N-38.5W.

Atmospheric Outlook for the Forecast Period...The intensifying 1002 mb frontal depression in the northeastern Atlantic...and intensifying 1004 mb frontal depression currently entering the Atlantic from the northeastern United States...will both weaken the Atlantic surface ridge. In turn this will cause Fiona to bend northward in track. Behind both frontal cyclones...a strong Atlantic surface ridge is expected to re-develop which will cause the track to bend back westward by 96 hours. Toward the end of the 120-hour forecast period...a bend back towards the north is likely as the vigorous frontal cyclone currently over western Canada dives into the western Atlantic and creates another ridge weakness. Fiona remains embedded in large-scale upper anticyclonic flow which is keeping vertical shear favorably low and upper outflow favorably high. However some cut-off upper vorticity lingers to Fiona's north currently structured as a pair of inverted upper troughs marked by blue-dashed lines in the atmospheric features chart above. This upper vorticity will retrograde westward with Fiona in the upper anticyclonic flow...with Fiona reaching the unfavorable upper vorticity by 48 hours after the track bends northward. This is why rapid weakening is shown in the 48 to 72 hour timeframe. By 96 hours this upper vorticity is shown in model runs to break up and diminish which could allow this tropical cyclone to survive through 120 hours. The intensity of Fiona toward the later part of the forecast period is uncertain as it is not clear yet if the upper vorticity producing the tropical disturbance south of Bermuda (area of interest #3 in the above atmospheric features chart) will linger and interefere with Fiona's development or not.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will be over favorable 28 deg C waters during the early part of the forecast period...reaching even more favorable 29 to 30 deg C waters by the end of the forecast period. Latest water vapor imagery (seen in the above thermodynamics chart) suggests Fiona is only an island of moisture surrounded by dry saharan air in the eastern and central tropical Atlantic. However as the above current prognosis states...Fiona has recently developed a ball of deep thunderstorms that could help it ward off this dry air for now. However by 48 hours as Fiona encounters westerly vertical shear from upper vorticity...the shear could waft in the unfavorable dry air.


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

24 Hr Forecast (0000Z Aug 19)...60 mph maximum sustained wind tropical storm centered at 17.5N-41W

48 Hr Forecast (0000Z Aug 20)...70 mph maximum sustained wind tropical storm centered at 21N-44W

72 Hr Forecast (0000Z Aug 21)...45 mph maximum sustained wind tropical storm centered at 24N-47.5W

96 Hr Forecast (0000Z Aug 22)...45 mph maximum sustained wind tropical storm centered at 24.5N-51.5W

120 Hr Forecast (0000Z Aug 23)...45 mph maximum sustained wind tropical storm centered at 27N-55W

Track Forecast...Although Fiona is slightly north of my previous forecast track. I have kept the track forecast the same for the early part of the forecast and kept it more south and west for the later part of the forecast period as most of the computer model runs have shifted to a more south and west long-range solution.

Intensity Forecast...Fiona is slighlty weaker than my previous forecast and so I have slighlty lowered the intensity forecast for 0000Z Aug 19. With the ball of deep thunderstorms that has recently developed as noted in the current prognosis...I still keep the same elevated intensity forecast for 0000Z Aug 20...followed by the same weaker forecast for 0000Z Aug 21 and beyond as Fiona encounters westerly vertical shear from upper vorticity (per the atmospheric outlook section above) and potential dry air intrusion (per the thermodynamic outlook section above).

Impact Forecast...My impact swath of tropical storm force winds in the above forecast graphic is the extrapolation of the 11 PM EDT NHC wind field along my forecast track and is made proportional to the forecast strength of the tropical cyclone...made wider where the storm is forecast to reach peak strength...and later narrowed to reflect expected weakening at the end of the forecast period.

2016 Atlantic Hurricane Season Birdseye Discussion #90

By: NCHurricane2009, 11:13 AM GMT on August 17, 2016

...WEDNESDAY AUGUST 17 2016 7:15 AM EDT...
Vigorous tropical wave Invest 98-L in the eastern tropical Atlantic spins up into the sixth tropical depression of the 2016 Atlantic Hurricane Season. See special feature section below for additional details on the new tropical cyclone and visit www.nhc.noaa.gov for up to the minute latest information on this tropical cyclone.

Also see the following statements for two other areas of interest following behind tropical depression six...

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic in the atmospheric features chart below. Satellite imagery suggests a tropical wave has recently emerged from western Africa while developing more vigorous thunderstorm activity. However the Euro (ECMWF) computer model which showed it gradually developing while moving toward the Lesser Antilles over the next several days is no longer showing such a solution. Instead it is possible this tropical wave gets absorbed by the larger tropical wave to the east mentioned in area of interest #2.

The follwoing statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. Yet another large and vigorous tropical wave over western Africa is shown to develop in some of the lastest computer model runs as it emerges into the Atlantic Ocean over the next few days. The Euro (ECMWF) and NAVGEM have a more northward solution while showing the wave spinning up over the Republic of Cabo Verde...whereas the GFS has a more southward soultion while showing the wave spinning up to the southwest of the Republic of Cabo Verde. Waiting for more consistency in the model runs and an assessment of the tropical wave structure when it enters the Atlantic before I upgrade this system 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 0600Z and 0728Z-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 SIX...
Current Prognosis...Vigorous tropical wave Invest 98-L in the eastern tropical Atlantic has spun up into the sixth tropical depression of the 2016 Atlantic Hurricane Season this past evening. The tropical depression has the classic apperance of a newly-developed tropical cyclone with sprial thunderstorm bands symmetrically wrapped around the center. As of 0600Z...satellite imagery suggested the center of tropical depression six was located at 12.6N-35W.

Atmospheric Outlook for the Forecast Period...The intensifying 1007 mb frontal depression in the north-central Atlantic...and intensifying 1006 mb frontal depression currently approaching the Atlantic from the northeastern United States...will both weaken the Atlantic surface ridge. In turn this will cause this tropical cyclone to bend northward in track. Behind both frontal cyclones...a strong Atlantic surface ridge is expected to re-develop which will cause the track to bend back westward at the end of the 120-hour forecast period. Tropical depression six remains embedded in large-scale upper anticyclonic flow which is keeping vertical shear favorably low and upper outflow favorably high. However some upper vorticity from the upper trough that is moving into Europe has cut-off in the form of an inverted upper trough marked as a blue-dashed line due north of the tropical depression in the atmospheric features chart above. This upper vorticity will retrograde westward with the tropical depression in the upper anticyclonic flow...with this tropical cyclone reaching the unfavorable upper vorticity by 72 hours after the track bends northward. This is why rapid weakening is shown in the 72 to 96 hour timeframe. However by 120 hours this upper vorticity is shown in model runs to break up and diminish which could allow this tropical cyclone to survive long after 120 hours.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will be over favorable 28 deg C waters during the 120-hour forecast period. Latest water vapor imagery (seen in the above thermodynamics chart) suggests this tropical cyclone is producing a well-defined moisture field that is repelling the dry saharan air in the eastern and central tropical Atlantic surrounding it. However by 72 hours as this tropical cyclone encounters westerly vertical shear from upper vorticity...the shear could waft in the unfavorable dry air.


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

24 Hr Forecast (0600Z Aug 18)...45 mph maximum sustained wind tropical storm centered at 14.5N-39.5W

48 Hr Forecast (0600Z Aug 19)...65 mph maximum sustained wind tropical storm centered at 17.5N-42W

72 Hr Forecast (0600Z Aug 20)...70 mph maximum sustained wind tropical storm centered at 21N-45W

96 Hr Forecast (0600Z Aug 21)...45 mph maximum sustained wind tropical storm centered at 26N-47.5W

120 Hr Forecast (0600Z Aug 22)...40 mph maximum sustained wind tropical storm centered at 27.5N-51.5W

Track Forecast...The tropical cyclone arrived to 35W longitude at 0600Z instaed of 0000Z like I previously forecasted...and therefore the tropical cyclone is currently east of my prior forecast. Also the tropical cyclone is 3.5N latitude further north than my prior foreacast. Therefore my updated forecast track shown above is adjusted northward and eastward accordingly.

Intensity Forecast...My updated intensity forecast is higher than the previous for the first part of the forecast period...but then is lowered for the later part of the forecast period as the northward adjusted forecast track brings the tropical cyclone more quickly into the less favorable upper vorticity to the north.

Impact Forecast...My impact swath of tropical storm force winds in the above forecast graphic is proportional to the forecast strength of the tropical cyclone...made wider where the storm is forecast to reach peak strength...and later narrowed to reflect expected weakening at the end of the forecast period.

2016 Atlantic Hurricane Season Birdseye Discussion #89

By: NCHurricane2009, 5:40 AM GMT on August 16, 2016

...TUESDAY AUGUST 16 2016 1:41 AM EDT...
The latest computer model runs suggest the potential for an Atlantic tropical cyclone outbreak to develop from vigorous tropical waves emerging from Africa. See the following statements for the first two such tropical waves...

The following statement concerns area of interest #1 marked over the eastern tropical Atlantic to the southwest of the Republic of Cabo Verde in the atmospheric features chart below. The vigorous tropical wave in this region continues to display a low pressure spin while safely passing south of the Republic of Cabo Verde. The tropical wave has been upgraded to disturbance Invest 98-L and many computer model runs suggest tropical cyclone formation from this system over the next few days. As such I have upgraded this tropical wave to a special feature on this blog with a tropical cyclone formation forecast. See the special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #2 marked over western Africa in the atmospheric features chart below. A tropical wave in this area is currently not well-organized or vigorous...but the usually conservative Euro (ECMWF) computer model over the last couple of days suggests possible tropical cyclone formation from this tropical wave as it moves across the tropical Atlantic and approaches the Lesser Antilles over the course of the next week.

...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...EASTERN ATLANTIC TROPICAL WAVE INVEST 98-L...
This special feature section is for area of interest #1 marked in the above atmospheric features chart.

Current Prognosis...A vigorous tropical wave in the eastern tropical Atlantic is moving briskly westward while passing south of the Republic of Cabo Verde. This tropical wave features strong shower and thunderstorm activity and a low pressure spin which intermittently shows organization in satellite frames. As of 0000Z...the low pressure spin was centered at 9N-28W. Twenty-four hours ago the low pressure spin was located at 21W longitude...and therefore the forecast track listed below is based on an initial 7W longitude per 24 hour motion.

Atmospheric Outlook for the Forecast Period...The 1014 to 1016 mb frontal depression which recently entered the Atlantic from the northeastern US...and 1012 mb frontal depression currently moving into the northeastern US from the Great Lakes/Ohio Valley region...are both expected to move and intensify rapidly across the north Atlantic which will weaken the Atlantic surface ridge. In turn this will cause this tropical wave to slow its westward progress and to bend northward in track during the forecast period. This tropical wave is currently embedded in large-scale upper anticyclonic flow which will keep vertical shear favorably low and upper outflow favorably high. Later in the forecast period...upper vortices originating from the northeastern Atlantic upper trough will retrograde westward in the upper anticyclonic flow...with this system reaching the unfavorable upper vorticity at the end of the forecast period. This is why rapid weakening is shown at the end of the forecast listed below.

Thermodynamic Outlook for the Forecast Period...On the forecast track this system will be over favorable 28 to 29 deg C waters during the 120-hour forecast period. Latest water vapor imagery (seen in the above thermodynamics chart) suggests the tropical wave is well-embedded in a moist air mass that could repel the dry saharan air in the eastern and central tropical Atlantic. However at the end of the forecast period as the tropical wave encounters westerly vertical shear from upper vorticity...the shear could waft in the unfavorable dry air.

24 Hr Forecast (0000Z Aug 17)...Organized tropical low centered at 9N-35W

48 Hr Forecast (0000Z Aug 18)...40 mph maximum sustained wind tropical storm centered at 11N-39.5W

72 Hr Forecast (0000Z Aug 19)...60 mph maximum sustained wind tropical storm centered at 14N-42W

96 Hr Forecast (0000Z Aug 20)...75 mph maximum sustained wind hurricane centered at 17.5N-45W

120 Hr Forecast (0000Z Aug 21)...50 mph maximum sustained wind tropical storm centered at 22.5N-47.5W

2016 Atlantic Hurricane Season Birdseye Discussion #88

By: NCHurricane2009, 10:04 PM GMT on August 14, 2016

...SUNDAY AUGUST 14 2016 6:04 PM EDT...
The following statement concerns area of interest #1 marked over southeastern Texas...Louisiana...and northwestern Gulf of Mexico in the atmospheric features chart below. The tropical disturbance that has persisted in this region has become less organized while a cold front from the northwest absorbs it. However the flood risk will not be over until the frontal zone leaves the area and all rainwater drains into the rivers over the next few days. The flood risk is spreading from southeastern Texas and Louisiana and into Arkansas...southeastern Missouri...southern Illinois...and southern Indiana as the tropical moisture and disturbance's low pressure center is being pulled northeastward by the frontal zone. This is my final statement on this disturbance on this blog...but areas in the aforementioned flood risk zone should listen to local news and national weather service over the next few days.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic to the southeast of the Republic of Cabo Verde in the atmospheric features chart below. A vigorous tropical wave that has recently emerged from western Africa is producing stronger and better organized showers and thunderstorms and the CMC and Euro (ECMWF) computer model runs suggest the possiblity of tropical cyclone formation. Atmospheric conditions are favorable with low shear and upper outflow supplied by an upper ridge expected to persist over the eastern tropical Atlantic...and latest water vapor imagery suggests the tropical wave is well-embedded in a moist air mass that could repel the dry saharan air in the central tropical Atlantic. Therefore if current organizational trends continue I will be upgrading it to a special feature on this blog with a tropical cyclone formation forecast. The 1007 mb frontal cyclone currently over the northeastern US will rapidly moves across the Atlantic and intensify...which will weaken the Atlantic surface ridge which in turn will cause this tropical wave to bend northward in track if it develops. Such a northward deflection in track would cause this system to pass over or just southwest of the Republic of Cabo Verde and therefore interests here should monitor this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1329Z-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).

2016 Atlantic Hurricane Season Birdseye Discussion #87

By: NCHurricane2009, 5:47 PM GMT on August 13, 2016

...SATURDAY AUGUST 13 2016 1:50 PM EDT...
The following statement concerns area of interest #1 marked over Louisiana and northwestern Gulf of Mexico in the atmospheric features chart below. An organized tropical disturbance persists in this area but its low pressure center is expected to continue northward into land...preventing tropical cyclone formation...while steered by the 1021 mb ridge over the western Atlantic. However this system remains a significant flooding concern as it has been slow-moving while producing persistent downpours. Flash flood watches and warnings are in effect for southern Louisiana at the present time.

The following statement concerns area of interest #2 marked over the eastern Caribbean Sea in the atmospheric features chart below. A surface trough persists in the area underneath favorable low shear and enhanced upper outflow supplied by an upper anticyclone that has developed in relatively higher pressures between the upper vortex over western Cuba and a developing upper vortex northeast of the Lesser Antilles. Although the unfavorable upper vortex over western Cuba is expected to continue westward and away...the upper vortex to the northeast is also expected to retrograde westward and could expand enough to interfere with development of this disturbance. Currently no computer models predict this disturbance to develop and its showers and thunderstorms have significantly weakened. 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 0600Z and 0730Z-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).

2016 Atlantic Hurricane Season Birdseye Discussion #86

By: NCHurricane2009, 2:19 AM GMT on August 12, 2016

...THURSDAY AUGUST 11 2016 10:20 PM EDT...
The following statement concerns area of interest #1 marked over the southeastern United States and northern Gulf of Mexico in the atmospheric features chart below. A tropical disturbance in this area remains organized underneath favorable low shear and outflow supplied by an upper anticyclone over the southeastern United States. The 1025 mb northwestern Atlantic ridge has steered the low pressure center of this disturbance northward and into land and therefore tropical cyclone formation will not occurr. However a flash flood watch is currently in effect for coastal northwestern Florida...coastal Mississippi...coastal Alabama...and southern Louisiana due to the fact that this slow-moving disturbance has been producing persistent downpours over the last few days.

The following statement concerns area of interest #2 marked over the Lesser Antilles and eastern Caribbean Sea in the atmospheric features chart below. A surface trough with increasingly organizing showers and thunderstorms has developed from the east side of a tropical wave over the last 48 hours. This new disturbance is being aided in a low shear and enhanced upper outflow environment in an upper anticyclone that has developed in relatively higher pressures between an upper vortex over Hispaniola and a developing upper vortex northeast of the Lesser Antilles. Although the unfavorable upper vortex over Hispaniola is expected to retrograde westward and away...the upper vortex to the northeast is also expected to retrograde westward and could expand enough to interfere with development of this disturbance. Currently no computer models predict this disturbance to develop.

...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).

2016 Atlantic Hurricane Season Birdseye Discussion #85

By: NCHurricane2009, 1:54 AM GMT on August 11, 2016

...WEDNESDAY AUGUST 10 2016 9:55 PM EDT...
The following statement concerns the weak tropical disturbance in area of interest #1 marked just north of the western Bahamas in the atmospheric features chart below. The 1026 mb ridge over the northwestern Atlantic is likely to send this disturbance northward parallel to the east United States coast. Showers and thunderstorms remain weak with this system and therefore it is unlikely that it will become a tropical cyclone before reaching the cooler waters in the northwestern Atlantic. This is my final statement on this blog regarding this disturbance.

The following statement concerns area of interest #2 marked over the southeastern United States and Gulf of Mexico. A tropical disturbance in this area remains organized underneath favorable low shear and outflow supplied by an upper anticyclone over the southeastern United States. Although this disturbance's low pressure center is along the Mississippi and Louisiana coast...the 1026 mb northwestern Atlantic ridge will soon steer this disturbance northward and into land. Therefore land interaction is expected to continue to prevent additional tropical development.

...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).

2016 Atlantic Hurricane Season Birdseye Discussion #84

By: NCHurricane2009, 5:05 AM GMT on August 10, 2016

...WEDNESDAY AUGUST 10 2016 1:10 AM EDT...
The following statement concerns the weak tropical disturbance in area of interest #1 marked just northeast of the Bahamas in the atmospheric features chart below. The 1023 mb ridge over the northeastern US is merging with the 1022 mb ridge over the western Atlantic...with with the west side of the combined ridge likely to send this disturbance northward parallel to the east United States coast. Showers and thunderstorms remain weak with this system and therefore it is unlikely that it will become a tropical cyclone before reaching the cooler waters in the northwestern Atlantic.

The following statement concerns area of interest #2 marked over the southeastern United States and eastern half of the Gulf of Mexico. A tropical disturbance in this area remains organized underneath favorable low shear and outflow supplied by an upper anticyclone over the southeastern United States. Although this disturbance's low pressure center has re-organized just offshore of northwestern Florida...the 1022 mb western Atlantic ridge and 1023 mb northeastern United States ridge are merging and will soon steer this disturbance northward and into land. Therefore land interaction is expected to continue to prevent additional tropical development.

...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).

2016 Atlantic Hurricane Season Birdseye Discussion #83

By: NCHurricane2009, 5:01 AM GMT on August 09, 2016

...TUESDAY AUGUST 9 2016 1:02 AM EDT...
The following statement concerns area of interest #1 marked just northeast of the Bahamas in the atmospheric features chart below. The tropical disturbance in this area continues drifting northwestward around the east side of an upper vortex offshore of northeast Florida. Over the next 24 hours...the 1021 mb ridge over the northeastern US will merge with the 1020 mb ridge over the western Atlantic...with with the west side of the combined ridge likely to continue the northwestward and north track of this disturbance parallel to the east United States coast. Showers and thunderstorms remain weak with this system and therefore it is becoming less likely that it will become a tropical cyclone before reaching the cooler waters in the northwestern Atlantic.

The following statement concerns area of interest #2 marked over the southeastern United States and eastern half of the Gulf of Mexico. A tropical disturbance in this area remains organized underneath favorable low shear and outflow supplied by an upper anticyclone over the southeastern United States. Although this disturbance continues to have a cloud swirl surface low...it is located over land while drifting westward which is preventing additional tropical development. After 24 hours...the 1020 mb western Atlantic ridge and 1021 mb northeastern United States ridge will merge over the Atlantic and steer this disturbance northward and further inland. Therefore land interaction is expected to continue to prevent additional tropical development.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1929Z-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).

2016 Atlantic Hurricane Season Birdseye Discussion #82

By: NCHurricane2009, 4:43 AM GMT on August 08, 2016

...MONDAY AUGUST 8 2016 12:50 AM EDT...
The following statement concerns area of interest #1 marked just northeast of the Bahamas in the atmospheric features chart below. The tropical disturbance that developed east of the Bahamas 24 hours ago is beginning to move northwestward around the east side of an upper vortex over the Bahamas. Over the next 48 hours...the 1020 mb ridge over the central US will merge with the 1020 mb ridge over the western Atlantic...with with the west side of the combined ridge likely to continue the northwestward and north track of this disturbance parallel to the east United States coast. Showers and thunderstorms did become concentrated and better organized this past morning and afternoon...but have weakened this evening. Combined with weak computer model support...I am not currently confident enough to upgrade this system to a special feature on this blog with a tropical cyclone formation forecast. However this disturbance bears close watching as it could quickly organize into a short-lived tropical cyclone before reaching cooler northwestern Atlantic waters...and if any signs of this starts to occur I will issue special updates or upgrade it to a special feature accordingly.

The following statement concerns area of interest #2 marked over Florida and northeastern Gulf of Mexico. A tropical disturbance in this area continues to organize underneath favorable low shear and outflow supplied by an upper anticyclone over the southeastern United States. Although this disturbance produced a cloud swirl surface low...it made landfall over northeastern Florida and southeastern Georgia which is preventing further tropical development at this time. During the next 48 hours this disturbance will continue to be generally stationary while trapped between the 1020 mb western Atlantic ridge and 1020 mb central United States ridge. By 72 hours this disturbance will move northward into the southeastern United States as the two ridges merge over the Atlantic and steer this disturbance. Land interaction with the northeastern US Gulf coast could continue limiting additional development....but should this disturbance further organize over water I will consider upgrading it 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 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).

2016 Atlantic Hurricane Season Birdseye Discussion #81

By: NCHurricane2009, 3:35 AM GMT on August 07, 2016

...SATURDAY AUGUST 6 2016 11:35 PM EDT...
Earl dissipates over south-central Mexico and merges with an eastern Pacific tropical disturbance located just offshore of Mexico's south coast.

Also see the following statements for three other areas of interest:

The following statement concerns area of interest #1 marked just east of the Bahamas in the atmospheric features chart below. The north side of a surface tropical wave is interacting with divergence between the east side of the upper vortex currently over the Bahamas...and west side of an upper anticyclone...which is resulting in somewhat organized showers and thunderstorms. The 1020 mb ridge over the central US and 1020 mb ridge over the western Atlantic are expected to merge over the next 72 hours...with the west side of this combined ridge likely to send this disturbance northward from the Bahamas and parallel to the east United States coast. If additional organization of this disturbance occurs...then I will consider upgrading it to a special feature on this blog with a tropical cyclone formation forecast.

The following statement concerns area of interest #2 marked over northwestern Florida and northeastern Gulf of Mexico. A tropical disturbance consisting of a surface trough has developed as the tail end of the lengthy north Atlantic cold front interacted with favorable low shear and upper divergence supplied by the upper anticyclone that has been centered near Mississippi over the past few days. During the next 72 hours this disturbance will be generally stationary while trapped between the 1020 mb western Atlantic ridge and 1020 mb central United States ridge. By 96 hours this disturbance will move northward into the southeastern United States as the two ridges merge over the Atlantic and steer this disturbance. Although this disturbance has become better organized over the last 24 hours...land interaction with the northeastern US Gulf coast could become a factor in limiting additional development. However should this disturbance further organize over water I will consider upgrading it 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 to the west-southwest of the Republic of Cabo Verde. The tropical wave in this region has become less organized while ingesting the stream of dry saharan air that has persisted in this region...and therefore this is my final statement on this blog on this tropical wave unless it re-organizes later.

...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).

2016 Atlantic Hurricane Season Birdseye Discussion #80

By: NCHurricane2009, 5:00 AM GMT on August 06, 2016

...SATURDAY AUGUST 6 2016 1:01 AM EDT...
After weakening across Belize...Guatemala...and the Yucatan peninsula...Earl quickly regains strong tropical storm strength while moving across the Bay of Campeche. Earl has just made its final landfall into east-central Mexico while continuing westward from the Bay of Campeche where tropical storm force winds with flash flooding and mudslide potential are expected in the next 24 hours. See special feature section below for additional details on Earl and continue to visit www.nhc.noaa.gov for up to the minute latest information on Earl.

Also see the following statements for four other areas of interest:

The following statement concerns area of interest #1 marked over the central tropical Atlantic just east of the Lesser Antilles in the atmospheric features chart below. The vigorous tropical wave that was briskly moving westward across this region has lost most of its shower and thunderstorm activity while ingesting dry saharan air...and is no longer a special feature on this blog. The GFS and European (ECMWF) computer model runs over the last day suggest this tropical wave may interact with the divergence on the east side of the upper vortex currently over the Bahamas...in which case a tropical disturbance could emerge. The 1020 mb ridge over the central US and 1021 mb ridge over the western Atlantic are expected to merge over the next few days...with the west side of this combined ridge sending such a tropical disturbance northward from the Bahamas and parallel to the east United States coast if this disturbance develops.

The following statement concerns area of interest #2 marked in the western Atlantic. The 1014 mb surface low that was offhore of North Carolina is currently at 1016 mb while moving eastward across the lengthy north Atlantic cold front. This surface low has left the large...favorable upper anticyclone currently centered over Mississippi...and will soon be accelerated northeastward toward cooler waters (the northeastward acceleration will be provided by the 992 mb frontal cyclone moving into eastern Canada). Therefore tropical cyclone formation from this feature is no longer possible and this is the final statement on this feature on this blog.

The following statement concerns area of interest #3 marked over parts of the southeastern United States and northeastern Gulf of Mexico. Yet another disturbance is emerging as the tail end of the lengthy north Atlantic cold front interacts with favorable low shear and upper divergence supplied by the upper anticyclone that has been centered near Mississippi/Lousiana over the past few days. The latest model runs of the CMC and European (ECMWF) sugest the potential for a tropical disturbance to develop in the northeastern Gulf of Mexico...in which case the disturbance will initially be stationary while trapped between the 1021 mb western Atlantic ridge and 1020 mb central United States ridge. Afterwards such a disturbance will move northward into the southeastern United States as the two ridges merge over the Atlantic and steer this disturbance.

The following statement concerns area of interest #4 marked over the eastern tropical Atlantic to the southwest of the Republic of Cabo Verde. Showers and thunderstorms associated with a tropical wave have increased while experiencing enhanced poleward upper outflow on the east side of an upper trough extending from a cut-off eastern Atlantic upper vortex. This favorable upper wind configuration is generally likely to continue while the upper trough is expected to seperate from the upper vortex and retorgrade westward at about the same pace as the tropical wave. However computer model support is currently lacking...perhaps as it is likely to ingest dry saharan air in the central tropical Atlantic like the recent tropical waves to the west have done...and therefore I am not upgrading this tropical wave to a special feature on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1920Z-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 EARL...
Current Prognosis...Over the last 48 hours Earl weakened to a tropical storm while moving across Belize...Guatemala...and the Yucatan peninsula of southeastern Mexico...but has maintained tropical storm strength as the circulation center straddles the southern Bay of Campeche coast of Mexico. This evening Earl has briskly re-strenghtened into a highly-organized tropical storm with 60 mph maximum sustained winds near the center. As of 0000Z the center of Earl passed over 18.8N-95.8w while making landfall into east-central Mexico.

Atmospheric Outlook for the Forecast Period...Earl is expected to continue westward further into east-central Mexico while steered by the west flank of the 1021 mb surface ridge across the Atlantic and south flank of the 1020 mb surface ridge over the central United States.

Thermodynamic Outlook for the Forecast Period...As Earl makes landfall and pushes further into east-central Mexico...water temps will no longer be relevant in the strength of Earl as it weakens over land.


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

24 Hr Forecast (0000Z Aug 7)...35 mph maximum sustained wind tropical depression dissipating into a remnant low over east-central Mexico at 19N-98.5W

Track Forecast...I have adjusted my forecast track southwestward based on the 0000Z center fix in the above current prognosis being south and west of my previous forecast in discussion #79...and based on current satellite loops which show Earl moving essentially due west along 19N latitude.

Intensity Forecast...Earl is expected to weaken to a tropical depression and then remnant low while moving further inland into east-central Mexico.

Impact Forecast...The impact swath in the above forecast graphic is based on gradually shrinking the current tropical storm radius along the forecast track as Earl is expected to weaken as it moves further inland into Mexico. In addition into tropical storm force winds...satellite imagery shows Earl has re-generated rather deep thunderstorms capable of flash flooding and mudslides as the tropical storm moves inland.

2016 Atlantic Hurricane Season Birdseye Discussion #79

By: NCHurricane2009, 8:08 AM GMT on August 04, 2016

...THURSDAY AUGUST 4 2016 4:10 AM EDT...
As expected Earl has become a hurricane making landfall in Belize this evening...becoming the first in-season (June to November) Atlantic hurricane of the 2016 season...and first hurricane in the Atlantic since Alex in January. The track has shifted a bit northward and therefore Earl could re-develop in the Bay of Campeche early this weekend...and therefore interests across Mexico's Bay of Campeche region should continue to monitor Earl carefully. See first special feature section below for more details on Earl...and visit www.nhc.noaa.gov for up to the minute latest information on Earl.

Also see the following statements for two other areas of interest:

The following statement concerns area of interest #1 marked over the central tropical Atlantic in the atmospheric features chart below. A vigorous tropical wave continues briskly westward across this region while continuing to show a low pressure spin. With atmospheric conditions over the tropical wave expected to remain favorable...will continue to watch this tropical wave as it moves across the tropical Atlantic and into the Caribbean Sea. See second special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #2 marked in the western Atlantic offshore of the Carolinas. A 1014 mb surface low at the tail end of the long cold front across the north Atlantic has moved offshore. While under the northeast side of the large...favorable upper anticyclone currently centered over Mississippi...it has a short window of time to acquire some tropical charactersitics before getting accelerated northeastward into cooler northwestern Atlantic waters (the northeastward acceleration will be provided when the pair of frontal cyclones over central Canada merge while moving into eastern Canada). So far there are no signs of this system gaining tropical characteristics.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0139Z-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 EARL...
Current Prognosis...Earl has strengthened into a rather well organized hurricane within the last 24 hours...and reached 80 mph maximum sustained winds while the eye made landfall near Belize City...Belize early this morning. As of 0000Z earlier this evening the center of Earl passed 17.5N-87.2W.

Atmospheric Outlook for the Forecast Period...Earl is expected to bend increasingly northward while rounding the southwest edge of the 1026 mb surface ridge stretched across the northern Gulf of Mexico and Atlantic. Earl has maintained a favorable upper anticyclone which will merge with the south side of the upper anticyclone currently centered over Mississippi. Therefore atmospheric conditions will remain highly favorable during the entire forecast period.

Thermodynamic Outlook for the Forecast Period...Very favorable 30 to 31 deg C waters lie along the projected path of Earl


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

24 Hr Forecast (0000Z Aug 5)...45 mph maximum sustained wind tropical storm centered over southeastern Mexico just north of Guatemala at 18.5N-91w

48 Hr Forecast (0000Z Aug 6)...50 mph maximum sustained wind tropical storm centered over the western Bay of Campeche at 19.5N-95W

72 Hr Forecast (0000Z Aug 7)...60 mph maximum sustained wind tropical storm centered over east-central Mexico at 20.5N-97.5W

96 Hr Forecast (0000Z Aug 8)...30 mph maximum sustained wind tropical depression dissipating into a remnant low over east-central Mexico at 22.2N-99W

Track Forecast...I have adjusted my forecast track 0.7 degrees northward based on the 0000Z center fix in the above current prognosis being 0.7N of the previous forecast.

Intensity Forecast...I have raised the intensity forecast for the late part of the forecast period as the northward adjustment in the track means a higher chance Earl re-develops over the Bay of Campeche early this weekend.

Impact Forecast...The impact swath in the above forecast graphic is based on gradually shrinking the current tropical storm radius along the forecast track as Earl is expected to weaken as it moves inland tonight. In addition to heavy rainfall with flash flooding potential...Earl is now more likely to bring tropical storm conditions to parts of Mexico's Bay of Campeche region if it redevelops this weekend.

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

Current Prognosis...A vigorous tropical wave is moving briskly westward across the central tropical Atlantic and continues to display a developing a low pressure spin estimated at 15N-42.5W as of 0000Z earlier this evening. This is quiet further north than yesterday's estimate as I was expecting the elongated circulation would consolidate further south toward the strongest thunderstorms of the tropical wave...but this has not occurred. Instead those thunderstorms have considerably weakened while the tropical wave ingests a patch of dry saharan air to its immediate northwest.

Atmospheric Outlook for the Forecast Period...This tropical wave is expected to continue westward across the tropical belt of the Atlantic and into the Caribbean Sea while steered by the 1026 mb Atlantic surface ridge. Atmospheric conditions will be favorable due to an upper ridge expanding from the eastern half of the tropcial Atlantic which will supply low shear and enhanced upper outflow. An inverted upper trough that was over the Florida straits has consolidated into an unfavorable upper vortex near the Bahamas while pushed around by Hurricane Earl's upper anticyclone...but the lastest model runs suggest this tropical wave will pass south of the upper vortex and maintain an upper anticyclone of its own at the end of the 120-hr forecast period...keeping conditions favorable. However I don't show tropical cyclone formation during the 120-hr forecast period due to current lack of computer model support and the fact that tropical waves moving briskly westward struggle to close off a surface circulation...for example what we recently saw with Hurricane Earl. Like Earl...tropical cyclone formation with this tropical wave is most likely just outside of the 120-hr forecast period when the tropical wave reaches weaker steering and slows down in the central or western Caribbean.

Thermodynamic Outlook for the Forecast Period...On the forecast track listed below...this tropical wave will be over favorable 28 to 30 C waters during the 120-hr forecast period. This tropical wave is currenlty struggling due to a patch of dry saharan air immediately to the northwest seen in the above thermodynamics chart...and latest water vapor imagery suggest patches of dry saharan air across the central tropical Atlantic...another reason I do not show tropical cyclone formation while this system crosses this area.

24 Hr Forecast (0000Z Aug 5)...Tropical low centered at 15N-50W

48 Hr Forecast (0000Z Aug 6)...Tropical low approaching the Lesser Antilles centered at 15N-57.5W

72 Hr Forecast (0000Z Aug 7)...Tropical low over the eastern Caribbean Sea at 15N-65W

96 Hr Forecast (0000Z Aug 8)...Tropical low over the central Caribbean Sea at 15N-71W

120 Hr Forecast (0000Z Aug 9)...Organizing tropical low over the central Caribbean Sea south of Jamaica centered at 16N-77W

2016 Atlantic Hurricane Season Birdseye Discussion #78

By: NCHurricane2009, 7:43 AM GMT on August 03, 2016

...WEDNESDAY AUGUST 3 2016 3:50 AM EDT...
Tropical wave Invest 97-L finally becomes Tropical Storm Earl while taking a more southward track...shifting the immediate threat away from the Cayman Islands and Yucatan peninsula of southeastern Mexico...and toward northern Honduras and Belize. Earl may rapidly strenghten into a hurricane in the next 24 hours which brings the threat of hurricane conditions to the islands offshore of Honduras and Belize. See first special feature section below for details on Earl and visit www.nhc.noaa.gov for up to the minute latest information on Earl.

Also see the following statements for three other areas of interest:

The following statement concerns area of interest #1 marked over the central tropical Atlantic in the atmospheric features chart below. Tropical wave Invest 96-L remains poorly-organized and its activity has become weaker...and therefore this is my final statement on this blog concerning this feature.

The following statement concerns area of interest #2 marked over the eastern tropical Atlantic in the atmospheric features chart below. A vigorous tropical wave continues briskly westward across this region while remaining organized and should continue to be monitored for development over the next few days as it moves across the tropical Atlantic and into the Caribbean Sea. See second special feature section below for additional details on this tropical wave.

The following statement concerns area of interest #3 marked over the eastern Carolinas. A 1014 mb surface low at the tail end of the long cold front across the north Atlantic is expected to move offshore in 48 to 72 hours. During this time the surface low will be under the northeast side of the large...favorable upper anticyclone currently centered over Louisiana and therefore could acquire some tropical charactersitics before getting accelerated northeastward into cooler northwestern Atlantic waters (the northeastward acceleration will be provided when the pair of frontal cyclones over central Canada and northwestern US merge while moving into eastern Canada). Will assess whether or not to issue a speical feature section depending on the condition of the surface low when it enters the Atlantic.

...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...TROPICAL STORM EARL...
Current Prognosis...Tropical wave Invest 97-L has finally become Tropical Storm Earl over the last 24 hours. The associated shower and thunderstorm activity has become more impressive this evening with an intense circular core of thunderstorms surrounded by outer spiral bands...and given the favorable atmospheric and thermodynamic conditions outlined below Earl is expected to become a hurricane and could even rapidly intensify into a high-end category 1 hurricane before making landfall in Belize (a category 2 cannot be ruled out). As of 0000Z earlier this evening the center of Earl passed 16.2N-82.2W.

Atmospheric Outlook for the Forecast Period...During the remainder of the forecast period...Earl is expected to bend increasingly northward while rounding the southwest edge of the 1023 to 1018 mb surface ridge stretched across the northern Gulf of Mexico and Atlantic. Earl has maintained a favorable upper anticyclone while passing south of the inverted upper trough over the Florida straits...and its favorable upper anticyclone will merge with the south side of the upper anticyclone currently centered over Louisiana during the later part of the forecast period. Therefore atmospheric conditions will be highly favorable during the entire forecast period.

Thermodynamic Outlook for the Forecast Period...Very favorable 30 to 31 deg C waters lie along the projected path of Earl


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

24 Hr Forecast (0000Z Aug 4)...90 mph maximum sustained wind hurricane centered at 16.8N-87.5W approaching Belize

48 Hr Forecast (0000Z Aug 5)...45 mph maximum sustained wind tropical storm centered over the northern Guatemala/Mexico border at 17.8N-91w

72 Hr Forecast (0000Z Aug 6)...35 mph maximum sustained wind tropical depression centered near the Mexico Bay of Campeche coast at 18.8N-95W

96 Hr Forecast (0000Z Aug 7)...35 mph maximum sustained wind tropical depression centered over east-central Mexico at 19.8N-97.5W

120 Hr Forecast (0000Z Aug 8)...Remnant low over east-central Mexico at 21.5N-99W

Track Forecast...I have adjusted my forecast track south and west of my previous based on the 0000Z center fix in the above current prognosis being south and west of my previous forecast.

Intensity Forecast...The only thing that will inhibit the strength of Earl will be interaction with land. Given the well-organized current structure I forecast Earl to briskly strengthen to a high-end category 1 hurricane in the next 24 hours before landfall in Belize...and this is higher than my previous intensity forecast for this timeframe. I have lowered the intensity forecast for the late part of the forecast period as the southward adjustment in the track will cause Earl to stay more over land and less over the Bay of Campeche water in that timeframe.

Impact Forecast...Earl is structured as a small tropical cyclone and therefore should only develop hurricane force winds in a tight area at the center. As such hurricane force winds are likely to develop and stay just offshore of the northern Honduras coast...but the development of hurricane force winds over the islands offshore of the Honduras coast cannot be ruled out if Earl rapidly intensifies in the next 24 hours. A tight area in east-central Belize should receive hurricane force winds at landfall. During the later part of the forecast period...while interacting with land...the only remaining impact will be heavy rainfall with flash flooding potential. See impact statement (b) in the above forecast graphic for regions expecting the rainfall.

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

Current Prognosis...A vigorous tropical wave is moving briskly westward across the eastern tropical Atlantic and continues to display a developing a low pressure spin estimated at 11N-32.5W as of 0000Z earlier this evening. Showers and thunderstorms remain the strongest and most organized on the south side of the developing spin.

Atmospheric Outlook for the Forecast Period...This tropical wave is expected to continue westward across the tropical belt of the Atlantic and into the Caribbean Sea while steered by the 1030 mb Atlantic surface ridge. Atmospheric conditions will be favorable for the duration of the 120-hr forecast period due to an upper ridge expanding from the eastern half of the tropcial Atlantic which will supply low shear and enhanced upper outflow. However I don't show tropical cyclone formation during the 120-hr forecast period due to current lack of computer model support and the fact that tropical waves moving briskly westward struggle to close off a surface circulation...for example what we recently saw with Tropical Storm Earl. Like Earl...tropical cyclone formation with this tropical wave is most likely just outside of the 120-hr forecast period when the tropical wave reaches weaker steering and slows down in the central or western Caribbean.

Thermodynamic Outlook for the Forecast Period...On the forecast track listed below...this tropical wave will be over favorable 29 to 30 C waters during the 120-hr forecast period. There is a patch of dry saharan air immediately north of the tropical wave...which maybe why thunderstorms are currently lacking in the north half of the tropical wave. Latest water vapor imagery suggest patches of dry saharan air across the central tropical Atlantic...another reason I do not show tropical cyclone formation while this system crosses this area.

24 Hr Forecast (0000Z Aug 4)...Tropical low centered at 11N-40W

48 Hr Forecast (0000Z Aug 5)...Tropical low centered at 11N-47.5W

72 Hr Forecast (0000Z Aug 6)...Tropical low centered at 11.5N-54W

96 Hr Forecast (0000Z Aug 7)...Tropical low passing over the southern Lesser Antilles and northeastern Venezuela centered at 12N-61W

120 Hr Forecast (0000Z Aug 8)...Tropical low centered over the southeastern Caribbean Sea at 12.5N-67.5W

2016 Atlantic Hurricane Season Birdseye Discussion #77

By: NCHurricane2009, 5:37 AM GMT on August 02, 2016

...TUESDAY AUGUST 2 2016 1:36 AM EDT...
The following statement concerns area of interest #1 marked over the central Caribbean Sea in the atmospheric features chart below. Tropical wave Invest 97-L on the cusp of being upgraded to a tropical storm...but regardless of tropical cyclone formation or not tropical storm conditions are expected to reach Jamaica...the Cayman Islands...northern Belize...and the Yucatan peninsula of southeastern Mexico in the next 48 hours. Interests in northern Belize...the Yucatan peninsula...and Mexico's Bay of Campeche coast should very carefully monitor this tropical wave as it could rapidly strenghten into a hurricane in rather favorable conditions should it establish a closed circulation and become a tropical storm. See first special feature section below for additional details on this developing situation...and visit www.nhc.noaa.gov in case this system gets upgraded to a tropical storm before my next full blog update.

The following statement concerns area of interest #2 marked over the eastern and central tropical Atlantic in the atmospheric features chart below. Tropical wave Invest 96-L has regained shower and thunderstorm activity but remains highly disorganized. Atmospheric conditions will become more favorable for development as the upper ridge currently in the eastern tropical Atlantic expands and overspreads this tropical wave. Therefore will continue to watch this tropical wave for any signs of re-organization over the next few days.

The following statement concerns area of interest #3 marked over the eastern tropical Atlantic in the atmospheric features chart below. The large tropical wave which recently emerged from Africa has become more compact and better organized this evening and therefore I have upgraded to a special feature on this blog. See second special feature section below for addtional details on this tropical wave.

The following statement concerns area of interest #4 marked over the east-central United States. A very long surface cold front trails from the 1000 to 1009 mb frontal cyclone in the north-central Atlantic. The CMC and more recently the Euro (ECMWF) computer models suggest that the tail end of the front currently over the east-central United States will move into the waters offshore of North Carolina in 72 to 96 hrs...during which time both models show the development of a surface low along the front. Such a surface low will be under the northeast side of the large...favorable upper anticyclone currently centered over Mississippi and therefore could acquire some tropical charactersitics before getting accelerated northeastward into cooler northwestern Atlantic waters (the northeastward acceleration will be provided by the frontal cyclone currently over western Canada when it later reaches eastern Canada). Will assess whether or not to issue a speical feature section for such a surface low if and when it forms.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1929Z-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 CARIBBEAN SEA 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 continues to move briskly westward across the Caribbean Sea while steered by the 1023 to 1028 mb surface ridge currently in the Atlantic. The associated shower and thunderstorm activity remains highly organized while resembling a tropical cyclone with a circular central dense overcast of thunderstorms...but the National Hurricane Center states that this system is not yet a tropical cyclone while lacking a closed surface circulation at this time. As of 0000Z earlier this evening...the center of the central dense overcast was southeast of Jamaica at 16.5N-75W. This system is producing squally weather across Jamica...eastern Cuba...the Dominican Republic...Haiti...and southeastern Bahamas. This tropical wave has reached tropical storm strength...and therefore regardless of tropical cyclone formation or not...it appears tropical storm conditions are expected across Jamaica...the Cayman Islands...the Yucatan peninsula of southeastern Mexico...and northern Belize over the next 48 hours. These areas should very carefully montior this system as tropical cyclone formation is possible at any time...in which case some brisk strengthening could occur given the highly-organized structure and favorable atmospheric and thermodynamic conditions that lie ahead. Some outer squally but less vigorous weather may also reach the Bahamas...western Cuba...and south Florida during the next 48 hours as well.

Atmospheric Outlook for the Forecast Period...During the remainder of the forecast period...the brisk westward track is expected to slow down and then bend increasingly northward while rounding the weaker southwest edge of the 1023 to 1028 mb surface ridge. This system has continued to develop beneath the favorable outflow and low shear of an upper anticyclone situated between a central Atlantic upper vortex and inverted upper trough over the Florida straits. During the later part of forecast period this tropical system will pass by the unfavorable aforementioned inverted upper trough and reach the favorable upper anticyclone that is currently centered over Mississippi. Because the 0000Z position was southeast of my prior forecast...I have slightly shifted the forecast track points slighlty south and east accordingly. I have also upped the intensity forecast for the timeframe that is currently at 48 hours because the more south forecast track would allow it to pass south of instead of through the unfavorable inverted upper trough...but it is possible this intensity forecast may be too low and this system reaches hurricane strength for landfall in the Yucatan if this system maintains a compact favorable upper anticyclone to the south of the inverted upper trough. I also show development into a hurricane in the Bay of Campeche due to forecast favorable upper anticyclonic flow on the south side of the large Mississippi anticyclone.

Thermodynamic Outlook for the Forecast Period...Another reason I have an elevated intensity forecast listed below is due to rather favorable 30 to 31 deg C waters that lies along the forecast track.

24 Hr Forecast (0000Z Aug 3)...50 mph maximum sustained wind tropical storm passing south of the Cayman islands centered at 17N-81W

48 Hr Forecast (0000Z Aug 4)...65 mph maximum sustained wind tropical storm centered at 17.5N-86.5W approaching northern Belize and the Yucatan peninsula of southeastern Mexico

72 Hr Forecast (0000Z Aug 5)...40 mph maximum sustained wind tropical storm centered over the western Yucatan peninsula at 18N-90w

96 Hr Forecast (0000Z Aug 6)...65 mph maximum sustained wind tropical storm in the Bay of Campeche centered at 19N-94W

120 Hr Forecast (0000Z Aug 7)...85 mph maximum sustained wind hurricane making landfall in east-central Mexico centered at 20.5N-96.5W

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

Current Prognosis...A tropical wave which has recently emerged into the eastern Atlantic from western Africa is passing south of the Repbulic of Cabo Verde while developing a low pressure spin estimated at 11.5N-24.5W as of 0000Z earlier this evening. Showers and thunderstorms are strongest on the south side of the developing spin and are beginning to show curvature as of 0300Z. As of 24 hours ago the tropical wave axis was at 17.5W longtitude...and therefore the forecast track below is based on the current 7W per 24 hour (17.5W to 24.5W) rate the tropical wave is currently moving at.

Atmospheric Outlook for the Forecast Period...This tropical wave is expected to continue westward across the tropical belt of the Atlantic while steered by the 1028 mb Atlantic surface ridge. Atmospheric conditions will be favorable for the duration of the 120-hr forecast period due to an upper ridge expanding across the eastern half of the tropcial Atlantic which will supply low shear and enhanced upper outflow. However I don't show tropical cyclone formation till 72 hours due to the current weak computer model support and the fact that tropical wave Invest 96-L to its west (area of interest #2) recently struggled to develop.

Thermodynamic Outlook for the Forecast Period...On the forecast track listed below...this tropical wave will be over favorable 27 to 29 deg C waters during the 120-hr forecast period. Tropical wave Invest 96-L to its west (area of interest #2) has mositened out a lot of the dry saharan air in the central tropical Atlantic...and so the forecast for now assumes dry air will not be a factor that inhibits development.

24 Hr Forecast (0000Z Aug 3)...Tropical low centered at 11.5N-31.5W

48 Hr Forecast (0000Z Aug 4)...Tropical low centered at 11.5N-38.5W

72 Hr Forecast (0000Z Aug 5)...35 mph maximum sustained wind tropical depression centered at 45.5W

96 Hr Forecast (0000Z Aug 6)...45 mph maximum sustained wind tropical storm centered at 12N-52.5W

120 Hr Forecast (0000Z Aug 7)...65 mph maximum sustained wind tropical storm approaching the southern Lesser Antilles centered at 12.5N-59.5W

2016 Atlantic Hurricane Season Birdseye Discussion #76

By: NCHurricane2009, 6:29 AM GMT on August 01, 2016

...MONDAY AUGUST 1 2016 2:30 AM EDT...
The following statement concerns area of interest #1 marked over the eastern Caribbean Sea in the atmospheic features chart below. Tropical wave Invest 97-L continues to become better organized and appears to be strengthening into a tropical storm while moving briskly across the eastern Caribbean. As such tropical storm warnings and watches may be raised at any time for southern Haiti...southern Dominican Republic...Jamaica...the Cayman Islands...and parts of Cuba and Yucatan peninsula of southeastern Mexico. Less vigorous and outer squally weather may also reach the Bahamas and south Florida over the next couple of days. In the long range (beyond 5 days)...interests in Mexico and Texas should monitor the progress of this tropical system as it may reach favorable conditions in the western Gulf of Mexico and strengthen. See special feature section below for additional details on this developing situation...and visit www.nhc.noaa.gov in case this system gets upgraded to a tropical storm before my next full blog update.

The following statement concerns area of interest #2 marked over the eastern and central tropical Atlantic in the atmospheric features chart below. Tropical wave Invest 96-L remains has become highly disorganzied and has lost almost all shower and thunderstorm activity perhaps while ingesting dry saharan air seen in the central tropical Atlantic on water vapor satellite imagery. Thus I have dropped it as a special feature on this blog as it is no longer at elevated risk of tropical cyclone formation. Atmospheric conditions will become more favorable for development as the upper ridge currently in the eastern tropical Atlantic expands and overspreads this tropical wave. Therefore will watch this tropical wave for any signs of re-organization over 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. A tropical wave with a rather large low pressure rotation is emerging from western Africa into a favorable environment provided by an upper ridge expanding across the eastern tropical Atlantic. I am currently not upgrading it to a special feature on this blog due to lack of computer model support and current weak state of shower and thunderstorm activity. However will watch this tropical wave for any signs of increasing organization 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 1923Z-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 SEA 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 continues to move briskly westward across the eastern Caribbean Sea while steered by the 1027 to 1025 mb surface ridge currently in the Atlantic. The associated shower and thunderstorm activity has continued to become better organized and now resembles a tropical cyclone with a circular central dense overcast of thunderstorms...but the National Hurricane Center states that this system is not yet a tropical cyclone while lacking a closed surface circulation at this time. As of 0000Z earlier this evening...the center of the central dense overcast was south-southwest of Puerto Rico at 16.5N-67.5W. This system is producing squally weather across Puerto Rico...Haiti...the Dominican Republic...and southeastern Bahamas. Regardless of tropical cyclone formation or not...it appears heavy weather will reach Jamaica...eastern Cuba...the Cayman Islands...and Yucatan peninsula of southeastern Mexico over the next couple of days. These areas should very carefully montior this system as tropical cyclone formation is possible at any time. Some outer squally but less vigorous weather may also reach the Bahamas...western Cuba...and south Florida during the next couple of days well.

Atmospheric Outlook for the Forecast Period...During the next 24 hours this tropical wave will continue briskly westward while continuing to be steered by the 1025 to 1027 mb Atlantic surface ridge. After that time the tropical wave is expected to slow down while arriving into the western Caribbean as it reaches weaker steering on the southwest edge of the aforementioned surface ridge. This system has continued to develop beneath the favorable outflow and low shear of an upper anticyclone situated between a central Atlantic upper vortex and inverted upper trough over the western Caribbean and western Bahamas. During the later part of forecast period this tropical system will pass trough the unfavorable aforementioned inverted upper trough and reach the favorable upper anticyclone that is currently centered over Louisiana. I have slightly shifted the forecast track northward since current organization suggests the circulation is already at 16.5N latitude. I have also upped the intensity forecast for the timeframe that is currently 24 hours and beyond since it appears tropical cyclone formation is already underway even though this disturbance has yet to slow down...but I do not show strengthening at the 48 to 72 hr timeframe as the more north track will allow it to interact with the less favorable inverted upper trough instead of passing south of the trough.

Thermodynamic Outlook for the Forecast Period...On the forecast track shown below...this tropical wave will track over rather favorable 30 to 31 deg C waters.

24 Hr Forecast (0000Z Aug 2)...45 mph maximum sustained wind tropical storm centered just offshore of the south coast of Jamaica at 17.5N-77W

48 Hr Forecast (0000Z Aug 3)...50 mph maximum sustained wind tropical storm centered just south of the Cayman islands at 18.5N-82W

72 Hr Forecast (0000Z Aug 4)...50 mph maximum sustained wind tropical storm centered at 19.5N-87W approaching the Yucatan peninsula of southeastern Mexico

96 Hr Forecast (0000Z Aug 5)...35 mph maximum sustained wind tropical depression centered at 20.5N-91W emerging into the western Gulf of Mexico from the northwestern Yucatan peninsula

120 Hr Forecast (0000Z Aug 6)...50 mph maximum sustained wind tropical storm in the western Gulf of Mexico centered at 22N-94W


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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