BIRDSEYE VIEW POSTS

Since 2012 on the Weather Underground (www.wunderground.com) blogs, I have been posting annotated "birdseye view" charts of the Atlantic basin, with a detailed explanation and forecasting that references the chart. From there you may know me as "NCHurricane2009." While I now do these "birdseye view" posts here, I will continue to do comments via Disqus on Weather Underground at www.wunderground.com/cat6. You can see my Disqus feed at this link for my latest comments. Feel free to reply to me with your disqus account or e-mail at IOHurricanes@outlook.com 

 
 
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MY 2020 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #57

Updated: Jul 10

*******Note that forecasts and outlooks in this post are NOT the official forecast from the National Hurricane Center (NHC). They are my own detailed views on the Atlantic tropics based on current observations and latest computer model runs. As such do not make decisions based on my posts...consult news media...watches and warnings from your local weather office...and any evacuation orders issued by local governments to make the most informed and best decisions. Visit the NHC website hurricanes.gov (hurricanes dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********


...THURSDAY JULY 9 2020 5:45 PM EDT...


See Tropical Storm Fay section below for more details on the only active tropical cyclone in the Atlantic basin. See area of interest sections below for additional area I am monitoring for tropical development in the coming days.


AREA OF INTEREST #1 (RECENTLY UPGRADED TO TROPICAL STORM FAY)...As of 2 PM EDT...the National Hurricane Center indicated that the broad surface low pressure that has been sitting over the Carolina coast over the lat day has finally developed a tightening circulation center over or just east of Cape Hatteras North Carolina...and the latest visible satellite animation suggests this continues to be the case. As of 5 PM EDT...aircraft reconaissance has verified this is also the case and that the surface low now qualifies to be Tropical Storm Fay...the earliest sixth tropical storm of an Atlantic Hurricane Season on record...beating Tropical Storm Franklin of 2005 which formed July 22 of that year! Fay continues to be supported by the eastern divergence zone of upper vorticity over the eastern United States...and this upper vorticity continues to keep the heaviest thunderstorm bands sheared off to the east side of the circulation. Even though in 24 hours I forecast the circulation center of Fay to be over cooler waters just southeast of New Jersey...I agree with the National Hurricane Center forecast for some strengthening to 50 mph maximum sustained winds as the eastern Untied States upper vorticity and apporaching large upper trough from western Canada will continue to support this system. I also keep Fay at tropical status during that time as the north-central United States frontal zone being driven by the large upper trough will still be off to the west...in other words considering that Fay will mimic Tropical Storm Edouard from a few days ago that strengthend under the support of upper troughing before it lost tropical characteristics. In 48 hours...Fay will have likely moved across the northeastern United States and into southeastern Canada...and I forecast Fay to weaken to a remnant low instead of strengthening as a non-tropical frontal low as the frotnal zone will still likely be off to the west...and also the NAVGEM and ECMWF have trended further east with their long term tracks which increases the probablity that Fay stays east of the frontal zone. It is a close call however...there is still some potential for Fay to instead strengthen over eastern Canada as a non-tropical frontal low as the 1200Z CMC model showed instead of dissipating just ahead of the front. Whether the long term track is further east or not will depend on if the large upper trough from western Canada phases with the eastern United States upper vorticity to become a more amplified upper trough capable of keeping Fay tugged further west. See bulletins on the home page of this site for expected impacts of Fay.

******Infohurricanes.com forecast. Visit hurricanes.gov (hurricanes dot gov) for official forecast***********

0 Hr Position (1800Z Jul 9)...45 mph maximum sustained wind tropical storm centered just east of Cape Hatteras North Carolina at 35.5N-74.5W

IOH 24 Hr Forecast (1800Z Jul 10)...50 mph maximum sustained wind tropical storm centered just southeast of New Jersey at 38.5N-74W

IOH 48 Hr Forecast (1800Z Jul 11)...Remnant low pressure centered over southeastern Quebec at 47N-71.5W


AREA OF INTEREST #2...Warm southerly flow on the east side of newly-formed Tropical storm Fay will amplify upper ridging currently over Florida into the northwestern Atlatnic...which will cause the shortwave upper trough currently exiting eastern North America to amplify into a cut-off upper vortex as it moves into the open central Atlantic. This will cause the formation of a surface frontal low offshore of Atlantic Canada in the next 24 hours...with the frontal low possibly acquring tropical characteristics in 3 to 5 days while it settles over central Atlantic waters of 23 deg C and a cold enough cut-off upper vortex to de-stabilize the atmosphere at these water temperatuers (forecasat to measure in the low 1200s of dekameters in height at 200 mb). Because all of the model runs agree with this general scenario...I have declared a new area of interest for tropical development. However I only give a 30% chance of subtropical cyclone formation as the GFS is the only model to show a strong enough circulation that suggests subtropical cyclone status while the other models show a weaker surface circulation. Forecast points in the outlook below are based on the location of the eastern divergence zone of the amplifying shortwave upper trough in the 1200Z GFS...followed by the position of the center of the upper vortex for the later part of the forecast as this system will whirl toward the center of the upper vortex as a classical post-mature frontal low pressure does. By 120 hours...the bullish GFS model shows the surface low weakening due to a lack of divergence beneath the upper vortex center as we typically see with post-mature frontal lows...so I drop the odds of subtropical cycloen formation starting at that time.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Jul 10)...0% chance of subtropical cyclone formation (northwestern Atlantic near 42.5N-50W)

IOH 48 Hr Outlook (1800Z Jul 11)...0% chance of subtropical cyclone formation(northwestern Atlantic near 41.5N-44.5W)

IOH 72 Hr Outlook (1800Z Jul 12)...30% chance of subtropical cyclone formation (central Atlatnic near 38N-42W)

IOH 96 Hr Outlook (1800Z Jul 13)...30% chance of subtropical cyclone formation (central Atlantic near 36N-42W)

IOH 120 Hr Outlook (1800Z Jul 14)...15% chance of subtropical cyclone formation (central Atlantic near 36N-43W)


AREA OF INTEREST #3...A tropical wave of low pressure moving through the central Caribbean Sea has quickly become organized in the last 24 hours while developing a spin with spiral thunderstorm bands...all supported by low shear and upper outflow of an upper ridge cell in the region. Based on satellite animation...the center of spin apperas to now be over land at the eastern Nicaragua/Honduras border. However because of offshore thunderstorm bands northeast of Honduras...I have some concerns that a new center could form over water in the next 24 hours capable of tropical cyclone formation...or alterntively the current center of spin might move close enough to the northern Honduras coast for development given that the wave is on the west extent of the steering Atlantic subtropical ridge where some northward angle in track could occurr. Therefore I give this tropical wave a 20% chance of tropical cyclone formation in the next 24 hours. After that time...landfall across Belize...Guatemala...and southeastern Mexico should preclude development...and upper vorticity over the Gulf of Mexico should also make upper winds unfavorable for development should the wave re-emerge over water in the southwestern Gulf of Mexico. In the impacts statement on the home page of this site...I do not mention impacts beyond Guatemala as the upper vorticity may suppress upper outflow needed for thunderstorm activity over southeastern Mexico.

******Infohurricanes.com outlook. Visit hurricanes.gov (hurricanes dot gov) for official outlook***********

IOH 24 Hr Outlook (1800Z Jul 10)...20% chance of tropical cyclone formation (east of Belize and north of Honduras near 16N-87.5W)

IOH 48 Hr Outlook (1800Z Jul 11)...0% chance of tropical cyclone formation (northwestern Guatemala near 17N-90.5W)


...COMPUTER MODEL SUMMARY...

Source...Florida State University Experimental Forecast Tropical Cyclone Genesis Potential Fields (http://moe.met.fsu.edu/tcgengifs/)


1200Z CMC Model Run...For area of interest #1...moves north-northeast to New Jersey coast in 36 hours...transitions into frontal low over eastern Canada by 78 hours as front currently approaching from the north-central United States overruns the circulation. For area of interest #2...frontal low becomes defined just east of Nova Scotia in 24 hours...becomes cut-off from the mid-latitude westerlies in 66 hours while located near 39.5N-41W...dissipates into a surface trough located within the Atlantic subtropical ridge near 41W longitude by 96 hours. For area of interest #3...no tropical cyclone formation shown


1200Z ECMWF Model Run...For area of interest #1...suggests strengthening while passing offshore of Maryland and Delaware in 48 hours...moves north-northeast across Cape Cod Massachusetts just before 72 hours...centered just offshore of New Jersey in 72 hours...loses its identity over Newfoundland within frontal system currently approaching from the north-central United States by 120 hours. For area of interest #2...frontal low becomes defined just south-southeast of Newfoundland in 48 hours...becomes cut-off from the mid-latitude westerlies in 72 hours while located near 41N-45W...dissipates into a surface trough located within the Atlantic subtropical ridge near 40W longitude by 120 hours. For area of interest #3...no tropical cyclone formation shown


1200Z GFS Model Run...For area of interest #1...suggests landfall on southern New Jersey in 30 hours...loses its identity over eastern Canada withing the currently approaching front from the north-central United States by 78 hours. For area of interest #2...frontal low becomes defined south of Newfoundland in 24 hours...becomes cut-off from the mid-latitude westerlies in 66 hours while located near 39.5N-43W...evolves into possible subtropical cyclone near 38.5N-41.5W in 78 hours. For area of interest #3...no tropical cyclone formation shown


1200Z NAVGEM Model Run...For area of interest #1...suggests landfall across Cape Cod Massachusetts in 48 hours...transitions into frontal low just north of Newfoundland by 90 hours as front currently approaching from the north-central United States overruns the circulation. For area of interest #2...frontal low becomes defined just south of Newfoundland in 24 hours...becomes cut-off from the mid-latitude westerlies in 66 hours while located near 40N-41W...dissipates into a surface trough located within the Atlantic subtropical ridge near 40W longitude by 132 hours. For area of interest #3...no tropical cyclone formation shown

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