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 #65

*******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.**********


...SUNDAY JULY 19 2020 1:12 PM EDT...

See area of interest section below for a disturbance being monitored for tropical cyclone formation. Elsewhere...conditions in the eastern tropical Atlantic to the south of the Republic of Cabo Verde Islands appear to be becoming gradually more favorable for tropical development as tropical waves of low pressure exiting Africa have been able to gradually increase thunderstorm activity to the southeast of the dry saharan air layer that has been dominating the region. In addition the tropical waves are being supported by a regime of low shear and upper outflow induced by a broad tropical upper ridge...and some of the recent computer model runs suggest possible development here in the coming days. Therefore should any signs of organization occur in the thunderstorm activity...will consider declaring another area of interest for tropical development.


AREA OF INTEREST #1...The north end of a tropical wave of low pressure that has been crossing the eastern Caribbean region has fractured into a seperate surface trough of low pressure producing a concentrated burst of thunderstorms east of the Bahamas...with increasing scattered thunderstorms popping up over the central Bahamas. This disturbance is moving through upper vorticity in the region...with the 0600Z GFS showing a 200 mb upper vortex center off to the northeast and water vapor animation suggesting another upper vortex to the northwest near the northwest Bahamas. Indeed based on the 0600Z GFS forecast...the upper vorticity is shown to split off into two vortices...one to the west and other to the east...with this disturbance potentially taking advantage of split flow upper divergence and low shear between the vortices in the next 24 hours. However I keep odds of tropical cyclone formation at 0% during that time as the disturbance is currently disorganized. This is an odd situation with the overall upper-level wind outlook becoming increasingly favorable for this disturbance to develop as the cold core upper vorticity is expected to continue breaking apart and weakening while remaining cut-off from the mid-latitudes by warm upper ridging over the southeastern United States...and yet (with the exception of the GFS on July 17) none of the models forecast this disturbance to develop. However given that the National Hurricane Center (NHC) has introduced this disturbance in their tropical weather outlook...I have declared it an area of interest for tropical development...with peak odds of trpoical cyclone formation at 30%...slightly higher than the 8 AM EDT NHC odds of 20% as the disturbance is alerady producing concentrated thunderstorms. I will only raise peak odds above 30% should the disturbance become better organized in the coming days and/or computer model support increases.


I keep odds of development at 0% through 48 hours as the disturbance moves into the western upper vortex. However after that time...I increase odds of development gradually to 30% as the western vortex is shown to gradually dissipate while shifting westward...increasingly placing the disturbance under favorable low shear and upper outflow beneath upper ridging extending from the southeastern United States and over very warm Gulf of Mexico water temperatures. Surface ridging is expected to remain north of the disturbance thru the forecast period while re-enforced by the western convergence zone of a pair of shortwave upper troughs to move across north America along the US/Canada border. Therefore the forecast track is west-northwest around the south periphery of the surface ridging.


Regardless of development...showers and vigorous thunderstorms are possible over the central and northwestern Bahamas...southern Florida...and western Cuba over the next couple of days. Interests along the south Texas coast should monitor the progress of this disturbance in the next few days as it is possible this disturbance develops into a tropical cyclone by then.

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

IOH 24 Hr Outlook (1200Z Jul 20)...0% chance of tropical cyclone formation (between Cuba and the eastern Bahamas near 22N-75W)

IOH 48 Hr Outlook (1200Z Jul 21)...0% chance of tropical cyclone formation (north coast of Cuba near 23N-80W)

IOH 72 Hr Outlook (1200Z Jul 22)...10% chance of tropical cyclone formation (southeastern Gulf of Mexico near 24N-85W)

IOH 96 Hr Outlook (1200Z Jul 23)...20% chance of tropical cyclone formation (central Gulf of Mexico near 25N-90W)

IOH 120 Hr Outlook (1200Z Jul 24)...30% chance of tropical cyclone formation (western Gulf of Mexico offshore of southern Texas near 26N-95W)


...COMPUTER MODEL SUMMARY...

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


0000Z CMC Model Run...For area of interest #1...no tropical cyclone formation shown. Elsewhere...develops tropical wave currently at 37.5W into a possible tropical cyclone near 9.5N-35W in 30 hours...feature crosses the Lesser Antilles at 14.5N-61W as a weaker tropical low pressure in 138 hours. In 72 hours suggests tropical wave will emerge from western Africa and move into the eastern tropical Atlantic as a broad tropical low pressure...tropical wave loses its well-defined state near 40W longitude by 156 hours without developing into a tropical cyclone.


0000Z ECMWF Model Run...For area of interest #1...no tropical cyclone formation shown.


0600Z GFS Model Run...For area of interest #1...no tropical cyclone formation shown. Elsewhere...develops tropical wave currently at 37.5W into a tropical low pressure near 10N-37W in 30 hours...tropical low dissipates near 11N-44W in 84 hours. In 48 hours suggests tropical wave will emerge from western Africa and move into the eastern tropical Atlantic as a broad tropical low pressure...tropical wave loses its well-defined state near 29W longitude by 84 hours without developing into a tropical cyclone.


0600Z NAVGEM Model Run...For area of interest #1...no tropical cyclone formation shown. Elsewhere...develops tropical wave currently at 37.5W into a tropical low pressure near 9N-34W in 12 hours...tropical low drifts east-northeast to 11N-32.5W by 48 hours...then begins moving westward and dissipates near 12.5N-40.5W in 114 hours. In 30 hours suggests tropical wave will emerge from western Africa and move into the eastern tropical Atlantic as a broad tropical low pressure...while cyclonically looping southeast of the Republic of Cabo Verde Islands the tropical low strengthens and reaches 14N-20.5W in 84 hours...crosses the southern islands by 96 hours...continues west and dissipates at 15.5N-36.5W in 156 hours.

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