NCHurricane2009's Blog

2016 Atlantic Hurricane Season Birdseye Discussion #23

By: NCHurricane2009, 12:42 AM GMT on May 31, 2016

...MONDAY MAY 30 2016 8:45 PM EDT...
Bonnie weakens to a remnant low over the eastern Carolinas. Additional showers and thunderstorms over the Carolinas will be possible over the next 72 hours as Bonnie remains stalled between the 1017 mb ridge over the southeastern US and 1028 mb ridge over the Atlantic. After that time...the 1006 mb surface frontal cyclone currently over the northwestern US will reach Bonnie and pull the remnants out to sea.

A surface trough northeast of the Bahamas continues to be supported by divergence between the east side of the cut-off upper trough from the southeastern United States to central Caribbean (marked by blue-dashed in the atmospheric features chart below) and west side of an upper ridge extending into the eastern Caribbean (marked by blue-zig-zag line). Showers and thunderstorms have become better organized around the surface trough this afternoon. Conditions for additional tropical development will only be favorable for another 48 hours after which time the cut-off upper trough de-amplifies which will result in increased unfavorable westerly vertical shear over this activity. However if current trends continue...I will consider upgrading this system to a special feature on my next blog post. If tropical cyclone development were to occur...it would most likely track northeastward (potentially toward Bermuda) across the western Atlantic while the aforementioned cut-off upper trough shifts eastward...and while rounding the west side of the Atlantic surface ridge. Any tropical cyclone that develops from this system should also remain weak due to the aforementioned expected westerly vertical shear.

As the cut-off upper trough over the southeastern US to central Caribbean Sea weakens...computer models show a favorable upper ridge developing over the western Caribbean Sea in its wake. The outflow of the upper ridge could keep surface pressures low...and a tropical wave reaching this region could become better organized and develop in about a week from now as some of the latest computer model runs suggest.

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #22

By: NCHurricane2009, 3:54 AM GMT on May 30, 2016

...SUNDAY MAY 29 2016 11:55 PM EDT...
Bonnie weakens to a tropical depression and then makes landfall in South Carolina. The tropical cyclone is expected to soon weaken to a remnant low. See special feature section below for additional details.

Showers and thundestorms continue to extend several hundred miles southeastward from Bonnie...to the northeast of the Bahamas and to the northeast of the eastern Caribbean. This activity is supported by divergence between the east side of the cut-off upper trough from the southeastern United States to central Caribbean (marked by blue-dashed in the atmospheric features chart below) and west side of an upper ridge extending into the eastern Caribbean (marked by blue-zig-zag line). A surface trough has developed northeast of the Bahamas...and another surface trough has developed north of the eastern Caribbean. None of the computer models suggest tropical cyclone development from either surface trough...and conditions will only be favorable for another 72 hours after which time the cut-off upper trough de-amplifies which will result in increased unfavorable westerly vertical shear over this activity.

As the cut-off upper trough over the southeastern US to central Caribbean Sea weakens...computer models show a favorable upper ridge developing over the western Caribbean Sea in its wake. The outflow of the upper ridge could keep surface pressures low...and a tropical wave reaching this region could become better organized and develop in a little over a week from now as some of the latest computer model runs suggest.

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 BONNIE...
Current Prognosis...On this evening's infrared satellite...Bonnie is a naked thin cloud swirl centered inland but close to the South Carolina coast with only one remain small clump of thick clouds over southwestern South Carolina. Visible imagery before sunset suggested that Bonnie's cloud swirl was de-generating into multiple swirls as the system continues to weaken. Radar shows skeletal bands of showers and weak thundertorms over eastern South and North Carolina. As of the 11 PM EDT National Hurricane Center advisory Bonnie was essentially stationary while centered at 32.8N-80.1W.

Atmospheric Outlook for the Forecast Period...The 1006 mb surface frontal cyclone and upper trough from the central US has merged with the cut-off upper trough that extends from the southeastern US to central Caribbean. The western convergence of both upper troughs have combined to create a 1020 to 1022 mb surface ridge over the southeastern US. Bonnie has once again stalled out this evening while becoming trapped between this ridge and the other 1026 mb surface ridge in the Atlantic. Over the next 24 hours the 1006 mb surface frontal cyclone will pass north of Bonnie while dragging Bonnie northeastward between the ridges. After that time as the frontal cyclone moves away...the gap between the ridges will close...and whatever is left of Bonnie will remain trapped over the eastern Carolinas. Then by 96 hours another frontal cyclone will pass north of Bonnie's remnants and whisk the remnants out to sea.

Thermodynamic Outlook for the Forecast Period...Bonnie will remain west of the warm Gulf stream waters which (in addition to land interaction) should prevent Bonnie from re-generating into a tropical cyclone after it dissipates.


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

24 Hr Forecast (0000Z May 31)...Remnant low centered inland in southeastern North Carolina but near the coast at 34.2N-78.5W

Track Forecast...Even though Bonnie is currently 0.4 degrees longitude west of my previous forecast track...I have adjusted my forecast track eastward as the latest satellite frames suggest Bonnie's cloud swirl is beginning to move northeastward along the South Carolina coast (and therefore I prefer to adjust my track to be near the coast).

Intensity Forecast...With Bonnie basically being a naked swirl (per the above current prognosis)...I expect Bonnie will soon be declared a remnant low.

Impact Forecast...Expect showers with isolated thunderstorms across the Carolinas as Bonnie continues to wind down. As noted in the above atmospheric outlook section...Bonnie could be stuck for about 96 hours...so its possible isolated flash flooding could occur in a heavy downpour that occurs over grounds that have already been saturated by Bonnie.

2016 Atlantic Hurricane Season Birdseye Discussion #21

By: NCHurricane2009, 4:19 AM GMT on May 29, 2016

...SUNDAY MAY 29 2016 12:20 AM EDT...
Tropical depression two strengthens to Tropical Storm Bonnie while temporarily stalling offshore of the South Carolina coast. Bonnie is expected to progress northward into the Carolina coast over the next couple of days. See special feature section below for additional details on the tropical storm. Visit www.nhc.noaa.gov for up to the minute latest information on Bonnie.

Showers and thundestorms continue to extend several hundred miles southeastward from Bonnie...to the norhteast of the Bahamas...and into the eastern Caribbean region. This activity is supported by divergence between the east side of the cut-off upper trough from the southeastern United States to central Caribbean (marked by blue-dashed in the atmospheric features chart below) and west side of an upper ridge extending into the eastern Caribbean (marked by blue-zig-zag line). The tropical wave currently just southeast of the Lesser Antilles may also aid in this activity over the next couple of days. So far there are no signs of tropical cyclone development in this activity but will continue to watch this area.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1921Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 BONNIE...
Current Prognosis...The cut-off upper vortex that was over the east coast of Florida has opened into an upper trough extending from the southeastern United States to the central Caribbean Sea (marked by blue dashed-line to the left of Bonnie in the atmospheric features chart above). Aicraft reconaissance this evening has verified tropical storm strength with 45 mph maximum sustained winds...and therefore tropical depression two is now Tropical Storm Bonnie. The tropical cyclone continues to have the same structure...a thin cloud swirl center with a clump of thunderstorms showing some curvature lopsided to the north of the swirl...although the clump is stronger and more impressive compared to yesterday. The reason the thunderstorms remain biased to the north half of the circulation is due to the ongoing southerly vertical shear imparted by the east side of the aforementioned cut-off upper trough. The thunderstorm activity has already made landfall ahead of the cloud swirl center...resulting in heavy rain bands across much of the state of South Carolina. Radar shows some outer rain bands beginning to spread into southeastern and southwestern North Carolina and into far eastern Georgia. As of 0000Z the center of Bonnie was located at 31N-79.5W...which is the same position it was a few hours ago which means Bonnie is stalled at the moment.

Atmospheric Outlook for the Forecast Period...Bonnie has been generally moving northwestward between the northeast side of the cut-off upper trough mentioned in the above current prognosis and southwest side of the 1026 mb Atlantic surface ridge. However this evening Bonnie has suddenly stalled...perhaps while running into a blocking surface ridge to the west in the Gulf of Mexico supported by the upper convergence on the back side of the cut-off upper trough (this surface ridge was marked with a red-zig-zag line across the Gulf in the atmospheric features chart in discussion #20). It appears the upper trough currently over the central US will quickly pass Bonnie to the north in the next couple of days...with upper convergence behind this upper trough and the aforementioned cut-off upper trough expanding weak surface ridging to the west of Bonnie. This will cause Bonnie to move slowly for the remainder of the forecast period while the storm gets trapped in conflicting steering between surface ridging to the west and the Atlantic surface ridge to the east. However a northward track is still expected as the upper trough from the central US and associated 1006 mb surface frontal cyclone guides Bonnie between the ridges...and perhaps Bonnie may hook rightward late in the forecast period while the upper trough/surface frontal cyclone moves northeastward and away.

Thermodynamic Outlook for the Forecast Period...Bonnie is now just west of the Gulf stream and is now over a narrow swath of water near the coast just below 26 deg C...and therefore additional strengthening is not expected.


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

24 Hr Forecast (0000Z May 30)...40 mph maximum sustained wind tropical storm centered just inland from the South Carolina coast...at 32.7N-79.7W

48 Hr Forecast (0000Z May 31)...Remnant low inland near the North Carolina/South Carolina border at 34.5N-79W

Track Forecast...Even though Bonnie is currently 1.5 degrees longitude west of my previous track...I am only doing a slight westward adjustment as Bonnie apparently has already stalled against some blocking surface ridging to the west per the above atmospheric outlook section. I have also adjusted my later forecast points to be further south...to reflect the effects of blocking surface ridging to the west which are apparently already affecting the storm motion...and to be more in alignment with the NHC and latest computer model runs. Also new to the late part of my forecast track is a rightward lean in accordance with the statement at the end of the above atmospheric outlook section.

Intensity Forecast...Slow weakening from this point forward is expected as Bonnie deals with water temps near the coast that are just below 26 deg C (per the above thermodynamic outlook)...southerly vertical shear (per the above current prognosis)...and landfall in the next 24 hours.

Impact Forecast...Impact swath is an extrapolation of the 11 PM EDT NHC tropical storm wind radius along my forecast track. It appears the main effect from this tropical cyclone is going to be heavy rain with flash flooding potential across much of South Carolina...as well as parts of North Carolina and perhaps far eastern Georgia.

2016 Atlantic Hurricane Season Birdseye Discussion #20A (Special Update)

By: NCHurricane2009, 4:33 PM GMT on May 28, 2016

...SATURDAY MAY 28 2016 12:33 PM EDT...
Visible satellite imagery this morning and early this afternoon shows that tropical depression two is tracking further west than previous forecasts from last evening. Therefore the amont of expected rain is decreasing for North Carolina and points north...and is increasing for eastern Georgia. Landfall will also occurr sooner and further to the south...perhaps by early tomorrow morning near the southern tip of South Carolina or the South Carolina/Georgia border. A landfall on the northern Georgia coast cannot be ruled out. Not much change in the expected weather for South Carolina with the threat of heavy rain and potential for some gusty winds on coastal regions. It is possible that gusty winds could also reach the northern Georgia coast at landfall.

My next full blog update on the Atlantic tropics will be later this evening. Return to full discussion #20 for an update on the rest of the Atlantic tropics. Continue to visit www.nhc.noaa.gov for up to the minute latest information on tropical depression two.

2016 Atlantic Hurricane Season Birdseye Discussion #20

By: NCHurricane2009, 3:04 AM GMT on May 28, 2016

...FRIDAY MAY 27 2016 11:05 PM EDT...
Tropical disturbance Invest 91-L has developed into tropical depression two this afternoon and is currently located north of the Bahamas and southeast of the Carolina coast. Heavy rainfall spreading into parts of the eastern United States and gusty winds reaching the Carolina coast are expected later this holiday weekend. See special feature section below for additional details. Visit www.nhc.noaa.gov for up to the minute latest information on this tropical cyclone.

Showers and thundestorms extend several hundred miles south from tropical depression two...across the eastern Bahamas...and into the eastern Caribbean region. This activity is supported by divergence between the east side of an upper vortex over the east coast of Florida (makred by blue L in the atmospheric features chart below) and west side of an upper ridge extending into the eastern Caribbean (marked by blue-zig-zag line). The tropical wave currently in the eastern Caribbean is also aiding this activity...and the tropical wave currently approaching the Lesser Antilles may also aid in this activity over the next couple of days. A tropical disturbance may emerge within this activity...especially in between the eastern Caribbean and Bermuda...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 1924Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 TWO...
Current Prognosis...The cut-off upper vortex that was over the western Bahamas has retrograded westward into the east coast of Florida (marked by blue L in the atmospheric features chart above). Aircraft reconaissance verified tropical depression strength and a closed circulation this past afternoon...which is why tropical disturbance Invest 91-L is now tropical depression two. A clump of thundertorms with some slight curvature is lopsided to the north of the circulation center due to southerly vertical shear imparted by the east side of the aforementioned upper vortex. As of 0000Z the center of the tropical depression was located at 28.8N-75.1W. Clusters of showers and thunderstorms extend several hundred miles to the south of the tropical depression and into the eastern Bahamas and eastern Caribbean region and are supported by upper divergence on the east side of an upper trough extending from the aforementioned upper vortex.

Atmospheric Outlook for the Forecast Period...Tropical depression two is expected to move northwestward into the Carolinas this holiday weekend while steered between the northeast side of the upper vortex mentioned in the above current prognosis and southwest side of the 1027 mb to 1024 mb eastern Canada to western Atlantic surface ridge.

Thermodynamic Outlook for the Forecast Period...During the next 24 hours...tropical depression two will cross the swath of Gulf stream waters exceeding 26 deg C while on its way to the Carolinas...which could help strengthen it to a tropical storm before its landfall in 48 hours.


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

24 Hr Forecast (0000Z May 29)...45 mph maximum sustained wind tropical storm centered offshore of the Carolinas at 31N-78W.

48 Hr Forecast (0000Z May 30)...45 mph maximum sustained wind tropical storm making landfall in northeastern South Carolina...centered at 33N-79W

72 Hr Forecast (0000Z May 31)...Remnant low centered over north-central North Carolina at 36N-79W

Track Forecast...My updated forecast track is basically a westward adjustment over my previous due to the 0000Z position (mentioned in the current prognosis above) being west of the previous forecast.

Intensity Forecast...I have lowered my intensity forecast and agree with the lastest National Hurricane Center intensity forecast which only shows the depression becoming a weak tropical storm before landfall. This is because the tropical depression is not too well organized on satellite imagery.

Impact Forecast...It appears the main effect from this tropical cyclone is going to be heavy rain with flash flooding potential spreading into the eastern United States from the Carolinas and perhaps some states to the north of the Carolinas...especially as this system merges with what has been a vigorous frontal system from the central United States which will be finally arriving into the eastern United States as this tropical cyclone makes landfall.

2016 Atlantic Hurricane Season Birdseye Discussion #19

By: NCHurricane2009, 1:55 AM GMT on May 27, 2016

...THURSDAY MAY 26 2016 9:56 PM EDT...
Tropical disturbance Invest 91-L located northeast of the Bahamas has become better organized while continuing to be supported by upper divergence on the east side of the upper vortex over the western Bahamas. Subtropical or tropical cyclone formation is expected within the next couple of days. Therefore interests over the southeastern United States should continue to monitor this situation carefully as preperations for a direct impact may be necessary starting tomorrow. See special feature section below for additional details on Invest 91-L.

Computer models suggest that a tropical disturbance could emerge in the western Atlantic between Bermuda and the eastern Caribbean Sea in about 5 days as the tropical wave currently midway between the Cape Verde Islands and Lesser Antilles moves into a highly divergent upper atmosphere near the eastern Caribbean Sea. This area of upper divergence will develop between the east side of the aforementioned cut-off upper vortex currently over the western Bahamas (marked by blue L in the atmospheric features chart below and expected to persist over the next several days) and northwest side of the upper ridge near the eastern Caribbean Sea (marked by blue zig-zag line and also expected to persist).

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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...SURFACE LOW INVEST 91-L...
Current Prognosis...A cut-off upper vortex centered over the western Bahamas persists (marked by blue L in the above atmospheric features chart). Divergence on the east side of the upper vortex continues to support tropical disturbance Invest 91-L. The disturbance has become better organized with a better-defined spin centered at 27.5N-70.5W as of 0000Z this evening. A burst of thunderstorms is just north of the center with lighter shower activity wrapping into the circulation from the east and southeast. Showers and thunderstorm activity is limited on the west and south sides of the circulation due to suppression from the aforementioned upper vortex.

Atmospheric Outlook for the Forecast Period...Latent heat release from Invest 91-L thunderstorm activity will build upper ridging to the east of the upper vortex and join upper ridging over the eastern US (marked by blue zig-zag line in the above atmoshperic features chart)...which will prevent the cut-off upper vortex from opening back into an upper trough during the forecast period. Meanwhile...surface ridging is expected to persist to the northeast of 91-L as the 1028 mb ridge currently over eastern Canada dives southeastward and merges with the 1025 mb Atlantic ridge. Therefore 91-L will move northwestward toward and eventually into the southeastern United States while steered between the northeast side of the upper vortex and southwest side of the surface ridge. Atmospheric conditions could become quiet favorable for tropical development and strengthening...especially toward the end of the forecast period...if enough upper ridging builds over the surface circulation. I have increased my intensity forecast due to the somewhat quickined pace of the organization observed this afternoon and evening. I have also adjusted my track forecast slightly eastward from my previous due to the current position being slightly east of the prior forecast. My solution is further north than solutions like the 1200Z GFS or 1200Z NAVGEM run which have the system more subtropical with the surface circulation eventually whirling southwestward into a position beneath the upper vortex. However with the recent burst of thunderstorms to the north of the upper vortex...I am more confident in a fully-tropical solution where the surface circulation perhaps reforms beneath the thunderstorms and becomes fully independent from the upper vortex while developing beneath upper ridging to the northeast of the upper vortex.

Thermodynamic Outlook for the Forecast Period...My updated forecast track keeps the circulation just north of the 26 deg C isotherm for the next 24 hours. By 48 hours the forecast track puts the circulation into favorable warm Gulf stream waters greater than 26 deg C and this is when I forecast some brisk intensification

24 Hr Forecast (0000Z May 28)...35 mph maximum sustained wind tropical depression centered northeast of the Bahamas at 28.5N-73W. Thunderstorms lopsided to northeast half of circulation due to upper vorticity to the southwest

48 Hr Forecast (0000Z May 29)...60 mph maximum sustained wind tropical storm centered offshore of the Carolinas at 31N-75W. Thunderstorms lopsided to the north half of the circulation due to upper vorticity to the south.

72 Hr Forecast (0000Z May 30)...65 mph maximum sustained wind tropical storm making landfall at Cape Lookout North Carolina...centered at 34N-76.5W

96 Hr Forecast (0000Z May 31)...Remnant low centered over eastern Virginia at 37.5N-77W

2016 Atlantic Hurricane Season Birdseye Discussion #18

By: NCHurricane2009, 3:00 AM GMT on May 26, 2016

...WEDNESDAY MAY 25 2016 11:01 PM EDT...
The cut-off upper trough over the western Caribbean Sea and Florida has organized into a cut-off upper vortex centered over the western Bahamas...and divergence on the east side of the upper vortex has supported the formation of tropical disturbance Invest 91-L at a location southwest of Bermuda. There is a high chance that 91-L transitions into a subtropical or tropical storm while moving into the southeastern United States this holiday weekend. Therefore interests over the southeastern United States should continue to monitor this situation carefully. See special feature section below for additional details on Invest 91-L.

Computer models suggest that a tropical disturbance could emerge in the western Atlantic between Bermuda and the eastern Caribbean Sea in about 6 days as the tropical wave currently southwest of the Cape Verde Islands moves into a highly divergent upper atmosphere near the eastern Caribbean Sea. This area of upper divergence will develop between the east side of the aforementioned cut-off upper vortex currently over the western Bahamas (marked by blue L in the atmospheric features chart below and expected to persist over the next several days) and northwest side of the upper ridge near the eastern Caribbean Sea (marked by blue zig-zag line and also expected to persist).

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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...SURFACE LOW INVEST 91-L...
Current Prognosis...The cut-off upper trough that was over the western Caribbean and Florida is beginning to close off into an upper vortex over the western Bahamas (marked by blue L in the above atmospheric features chart). Divergence on the east side of the upper vortex continues to support thunderstorm activity to the southwest of Bermuda...and visible satellite imagery suggests the decaying surface front in the region has organized into a 1017 mb weak surface low pressure spin embedded in these thunderstorms...centered at 26.5N-68W as of 0000Z this evening. This surface low has been upgraded to Invest 91-L on the Naval Research Laboratory (NRL) site of the US Navy. Additional widespread thunderstorm activity is occuring much further south over the central Caribbean Sea and part of South America...but this is seperate from Invest 91-L in association with a tropical wave interacting with the divergent upper atmosphere on the east side of an upper trough extending from the upper vortex.

Atmospheric Outlook for the Forecast Period...The cut-off upper trough supporting Invest 91-L has already closed off into an upper vortex per the above current prognosis...due to the amplifying upper ridge over the eastern US supported by warm air advection ahead of the 1005 mb frontal cyclone currently over the north-central US. Latent heat release from Invest 91-L thunderstorm activity will build upper ridging to the east of the upper vortex and join the aforementioned upper ridging over the eastern US...which will prevent the cut-off upper vortex from opening back into an upper trough during most of the forecast period. Meanwhile...surface ridging is expected to persist to the northeast of 91-L as the 1028 mb ridge currently over eastern Canada dives southeastward and merges with the 1030 mb Atlantic ridge. Therefore 91-L will move northwestward toward and eventually into the southeastern United States while steered between the northeast side of the upper vortex and southwest side of the surface ridge. Atmospheric conditions could become quiet favorable for tropical development and strengthening...especially toward the end of the forecast period...if enough upper ridging builds over the surface circulation. However I have lowered my intensity forecast due to a northward adjustment in track which keeps the circulation over cooler waters and has the circulation making landfall sooner than my previous forecast. The northward adjustment is due to the lastest current prognosis which has the surface circulation already to the north of my previous forecast.

Thermodynamic Outlook for the Forecast Period...My updated forecast track keeps the circulation just north of the 26 deg C isotherm for the next 48 hours. By 72 hours the forecast track puts the circulation into warm Gulf stream waters greater than 26 deg C and this is when I still forecast tropical cyclone formation.

24 Hr Forecast (0000Z May 27)...Surface low centered northeast of the Bahamas at 27.5N-71W

48 Hr Forecast (0000Z May 28)...Surface low centered northeast of the Bahamas at 28.5N-74W. Thunderstorms lopisided to northeast half of circulation due to upper vorticity to the southwest

72 Hr Forecast (0000Z May 29)...50 mph maximum sustained wind tropical storm centered offshore of the Carolinas at 31N-76.5W. Thunderstorms lopsided to the north half of the circulation due to upper vorticity to the south.

96 Hr Forecast (0000Z May 30)...50 mph maximum sustained wind tropical storm making landfall between Cape Lookout and Wilmington North Carolina...centered at 34N-77.5W

120 Hr Forecast (0000Z May 31)...Remnant low centered over Virginia at 37.5N-78W

2016 Atlantic Hurricane Season Birdseye Discussion #17

By: NCHurricane2009, 3:43 AM GMT on May 25, 2016

...TUESDAY MAY 24 2016 11:44 PM EDT...
After Hurricane Alex in January...potentially gearing up for what could one of the most active starts to the Atlantic Hurricane Season on record due to the following two risk areas that could develop in late May and early June:

A cut-off upper trough persists from the western Caribbean Sea to Florida (marked by blue-dashed line in the atmopsheric features chart below). Divergence on the east side of this cut-off upper trough is supporting an area of strong thunderstorms over eastern Cuba..the eastern Bahmas...and western Atlantic to the southwest of Bermuda. Surface convergence from the tail end of the cold front associated with the 1011 mb deep-layered low over Massachusetts is also aiding this activity...and the tail end of this front could evolve into a subtropical or tropical system supported by the aforementioned upper divergence. If so...this subtropical or tropical system would approach the southeastern United States this holiday weekend. Interests over the southeastern United States should monitor this situation carefully over the next few days. See special feature section below for additional details.

Computer models suggest that the tropical wave currently southwest of the Cape Verde Islands will move into a highly divergent upper atmosphere near the eastern Caribbean Sea by next week. This area of upper divergence will develop between the east side of the aforementioned cut-off upper trough/vortex currently near Florida (marked by blue-dashed line and expected to persist over the next several days) and northwest side of the upper ridge near the eastern Caribbean Sea (marked by blue zig-zag line and also expected to persist). If this verifies...tropical cyclone formation will be possible in the western Atlantic near the eastern Caribbean Sea sometime next week.

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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...CUT-OFF UPPER TROUGH...
Current Prognosis...A cut-off upper trough persists from the western Caribbean Sea to Florida (marked by blue-dashed line in the above atmospheric features chart). Divergence on the east side of this cut-off upper trough is supporting thunderstorm activity. Latest satellite imagery shows one mass of thunderstorms to the southwest of Bermuda and a second mass over Jamaica and eastern Cuba. Surface convergence from the tail end of the cold front associated with the 1011 mb deep-layered low over Massachusetts is also aiding this activity.

Atmospheric Outlook for the Forecast Period...Computer models suggest that latent heat release from the thunderstorm activity will build upper ridging to the east of the cut-off upper trough. As this upper ridging joins upper ridging over the eastern United States...this will cause the upper trough to further cut-off into a closed upper vortex. Meanwhile...surface ridging is expected to persist to the northeast of this system thru the forecast period as the 1023 mb ridge currently over eastern Canada dives southeastward and merges with the 1032 mb Atlantic ridge. Therefore there is a very high chance of this system moving northwestward toward and eventually into the southeastern United States while steered between the northeast side of the forecast upper vortex and southwest side of the surface ridging. Atmospheric conditions could become quiet favorable for tropical development and strengthening...especially toward the end of the forecast period...if enough upper ridging builds over the surface circulation per the aforementioned latent heat process. Therefore I am currently forecasting a strenghtening tropical storm moving toward the southeastern United States as shown below.

Thermodynamic Outlook for the Forecast Period...If the forecast track below verifies...this system will be over 26 deg C or greater water temps supportive for tropical development.

24 Hr Forecast (0000Z May 26)...Area of thunderstorms and broad low surface pressures over eastern Cuba...eastern Bahamas...and western Atlantic supported by divergence on the east side of upper trough. Upper trough transitioning to upper vortex centered over the western Bahamas

48 Hr Forecast (0000Z May 27)...Area of thunderstorms and north-south surface trough over the eastern Bahamas and western Atlantic...supported by divergence on the east side of upper vortex centered near the western Bahamas

72 Hr Forecast (0000Z May 28)...Surface low forming just northeast of the central Bahamas...centered at 25N-75W. Thunderstorms lopisided to northeast half of circulation due to upper vorticity to the southwest

96 Hr Forecast (0000Z May 29)...50 mph maximum sustained wind tropical storm centered north of the western Bahamas at 28.5N-77.5W. Thundersorms lopsided to the north half of the circulation due to upper vorticity to the south.

120 Hr Forecast (0000Z May 30)...65 mph maximum sustained wind tropical storm moving northwestward toward Carolinas...centered at 32N-79W

2016 Atlantic Hurricane Season Birdseye Discussion #16

By: NCHurricane2009, 5:48 AM GMT on May 24, 2016

...TUESDAY MAY 24 2016 1:50 AM EDT...
The upper vortex that was over the eastern United States has moved offshore while becoming vertically aligned with the 1006 mb surface frontal low offshore of North Carolina...resulting in a deep-layered circulation. However there are no signs of subtropical development from this deep-layered low...and subtropical cyclone formation is not expected as it moves northward into Massachusetts in the next 24 hours.

The southern part of the aforementioned large deep-layered circulation has become a seperate cut-off upper trough currently spanning from Florida to the western Caribbean Sea (marked by blue-dashed line in the atmopsheric features chart below). Divergence on the east side of this cut-off upper trough should keep surface pressures low to the northeast of the Bahamas and offshore of the southeastern United States...and the latest computer models suggest subtropical or tropical development in this region occurring in as little as 4 to 5 days from now. Stay tuned.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0135Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #15

By: NCHurricane2009, 3:07 AM GMT on May 23, 2016

...SUNDAY MAY 22 2016 11:07 PM EDT...
The upper trough over the eastern United States has evolved into a cold core upper vortex (marked by blue L in the atmospheric features chart below). Divergence on the east side of the upper vortex is supporting an intensifying 997 mb frontal cyclone that is moving northeastward offshore of the northeastern United States...as well as a new 1007 mb surface frontal low offshore of North Carolina. Although the cold temps and low vertical shear of the upper vortex (coupled with the warm Gulf stream waters offshore of the Carolinas) are favorable for some subtropical development of the 1007 mb surface low...this surface low will already be moving northward toward cooler waters and into Massachusetts in 48 hours. Therefore subtropical cyclone formation here is not expected.

Over the course of the next week...the southern part of the large upper vortex over the eastern United States is expected to develop into a separate cut-off upper trough in the vicinity of the Bahamas. Divergence on the east side of this cut-off upper trough should keep surface pressures low to the northeast of the Bahamas and offshore of the southeastern United States and subtropical or tropical development in this region may be possible as we approach the official start of the hurricane season on June 1st.

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #14

By: NCHurricane2009, 9:00 PM GMT on May 21, 2016

...SATURDAY MAY 21 2016 5:05 PM EDT...
An upper trough over the eastern US currently stretches from Florida to the Ohio Valley (marked by blue-dashed line in the atmospheric features chart below). Divergence on the east side of this upper trough is supporting a 1013 mb surface frontal low that will intensify as it moves northeastward. The upper trough is forecast to evolve into a cold core upper vortex whose eastern divergence will support the formation of another surface low offshore of North Carolina in 48 hours. Although it is possible the cold temps and low vertical shear of the upper vortex (coupled with the warm Gulf stream waters offshore of the Carolinas) could help in subtropical development of this surface low...computer models agree that this surface low will have already moved northward toward cooler waters and into Massachusetts by 72 hours. Therefore chances remain low that subtropical development will occur.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1337Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #13

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

...SATURDAY MAY 21 2016 12:50 AM EDT...
A cut-off upper trough over the eastern US currently stretches from Louisiana to Wisconsin (marked by blue-dashed line in the atmospheric features chart below). Divergence on the east side of this upper trough is supporting a 1013 mb surface frontal low that will intensify as it moves northeastward. The upper trough is forecast to evolve into a cold core upper vortex whose eastern divergence will support the formation of another surface low offshore of North Carolina in 72 hours. Although it is possible the cold temps and low vertical shear of the upper vortex (coupled with the warm Gulf stream waters offshore of the Carolinas) could help in subtropical development of this surface low...computer models agree that this surface low will have already moved northward toward cooler waters and into Massachusetts by 96 hours. Therefore chances remain low that subtropical development will occur.

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #12

By: NCHurricane2009, 1:34 AM GMT on May 20, 2016

...THURSDAY MAY 19 2016 9:40 PM EDT...
The tail end of a cold front currently over the southwestern US and US Gulf coast has potential to evolve into a subtropical system offshore of the southeastern United States in about four days. The tail end of the upper trough associated with this cold front has evolved into a cut-off upper trough currently stretching from Texas to Nebraska (marked by blue-dashed line in the atmospheric features chart below). The cut-off upper trough is forecast to evolve into a cold core upper vortex whose eastern divergence will support the formation of one or two surface lows along the cold front that will start over the southeastern US and move offshore of the Carolinas in four days. It is possible the cold temps and low vertical shear of the upper vortex...coupled with the warm Gulf stream waters offshore of the Carolinas...will de-stabilize the atmosphere and cause one of the surface lows to evolve into a subtropical cyclone during this time. However most computer models have backed off of this scenario except for the less-reliable NAVGEM...and therefore chances remain low that this scenario will occur.

...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.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #11

By: NCHurricane2009, 11:42 AM GMT on May 19, 2016

...THURSDAY MAY 19 2016 7:43 AM EDT...
The heavy thunderstorms that were offshore from the east coast of Florida have organized into a 1008 mb surface frontal low that is moving rapidly northeastward and will soon pass north of Bermuda later today. Tropical cyclone formation is not expected here.

The tail end of a cold front currently over the southwestern United States has potential to evolve into a subtropical system offshore of the southeastern United States in about five days. The tail end of the upper trough associated with this cold front has begun to evolve into a cut-off feature currenlty located over the southwestern US...and is forecast to evolve into a cut-off cold core upper vortex whose eastern divergence will support the formation of one or two surface lows along the cold front that will start over the southeastern US and move offshore of the Carolinas in five days. It is possible the cold temps and low vertical shear of the upper vortex...coupled with the warm Gulf stream waters offshore of the Carolinas...will de-stabilize the atmosphere and cause one of the surface lows to evolve into a subtropical cyclone during this time. However most computer models have backed off of this scenario except for the less-reliable NAVGEM...and therefore chances are decreasing that this scenario will occur.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z and 0737Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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 #10

By: NCHurricane2009, 4:20 AM GMT on May 18, 2016

...WEDNESDAY MAY 18 2016 12:25 AM EDT...
Monitoring two areas along a surface cold front currently strung across the United States Gulf coast and southwestern United States.

Heavy thunderstorms along the cold front...supported by upper divergence on the east side of a shortwave upper trough...have moved across the Gulf of Mexico and the Florida Peninsula over the last 48 hours. Recently this mass of thunderstorms has become better organized while joining shower activity that was over the southeastern United States and is expected to organize into a surface low offshore of the southeastern United States that will accelerate northeastward to the north of Bermuda and into the northwest Atlantic over the next 72 hours. High amounts of westerly vertical shear and increasingly cooler waters should prevent tropical development of this activity. However the fast northeast track of this system is allowing this system to somewhat match the upper-level westerly wind speed which might be reducing the shear a bit...so will watch it carefully over the next day or so before it reaches cooler waters.

The other area of concern is the tail end of the cold front currently over the southwestern United States. This cold front is supported by a southwest-northeast oriented upper trough from southern Utah reaching all the way into eastern Canada (marked by blue-dashed line in the atmospheric features chart below). Computer models agree that the tail end of the upper trough will evolve into a cut-off cold core upper vortex whose eastern divergence will support the formation of one or two surface lows along the cold front that will start over the southeastern US and move offshore of the Carolinas in six days. It is possible the cold temps and low vertical shear of the upper vortex...coupled with the warm Gulf stream waters offshore of the Carolinas... will de-stabilize the atmosphere and cause one of the surface lows to evolve into a subtropical cyclone during this time. Stay tuned 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 0128Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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, blue Hs are locations of upper ridges.

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, Hs indicate surface highs.

...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).


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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