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 #172A (Special Update)

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


...SATURDAY NOVEMBER 7 2020 6:02 PM EDT...

Satellite image of Tropical Storm Eta as of 2210Z:


Eta strengthens quickly and moves faster...I feel these changes warrant a special update to warn many in the path of the storm of now possible hurricane conditions and the sooner arrival of severe weather conditions given that I have yet to complete my next full update. I still plan to release my full update on the rest of the Atlantic tropics tonight. Feel free to skip to the bulletins at the end of this message for an updated summary of expected impacts given the latest with Eta.


Throughout the late morning and afternoon while the center of Eta passed just north of the Cayman Islands...it has re-intensified in dramatic fashion from a disorganized tropical depression to what is now a strong tropical storm. This has been made possible by a circular thunderstorm mass that covered the center of circulation...which is ventilated at the upper levels by divergence on the east side of the amplified cut-off upper trough centered over Louisiana and some anticyclonic warm core outflow located east of the upper trough. This thunderstorm mass is also not large and sprawling in nature such that the storm has taken on a more compact structure with a tighter pressure gradient needed for higher winds. As Eta continues northward around the east side of the cut-off upper trough and across central Cuba and toward the western Bahamas and south Florida...this upper air pattern will continue and therefore it is more probable that Eta becomes a hurricane as reflected in my updated forecast below. Forecast track is much the same as the previous...but shows Eta reaching the western Bahamas and south Florida sooner given Eta’s current position.


After 24 hours...a deep-layered ridge will have built over the eastern United States...to the north of Eta and the cut-off upper trough. At the surface...there is already a strong ridge over the eastern United States supported by the western convergence zone of the current upper trough moving across eastern Canada. A strong surface frontal system/upper trough over the western US will pivot into the central US while advecting plenty of warm air northward...inducing an upper-level ridge over the eastern United States...which will cause the cut-off upper trough to amplify into an upper vortex. The upper vortex in combination with the deep-layered eastern United States ridge should whirl Eta into south Florida and/or the Florida Keys by 48 hours...and eastern Gulf of Mexico by 72 hours. A northward angle in track is probable through 72 hours as the models continue to trend in showing the vigorous frontal system/upper trough over the central United States moreso weakening the eastern United States deep-layered ridge. It is also during this time I do not forecast Eta to be above minimal hurricane status as the upper vortex would suppress Eta’s southern warm core upper outflow. Land interaction with the southern Florida peninsla at 48 hours should also be a limiting factor. After 72 hours...because the central US upper trough is currently forecast to moreso weaken the eastern United States deep-layered ridge...the upper trough is likely to reverse the upper flow in the eastern Gulf of Mexico a westerly shearing direction such that I drop the intensity forecast back to tropical storm status. It also appears likely for now that Eta gets pulled northeast by the upper trough and its surface cold front into northern Florida by 120 hours...with the combo of land interaction and shear weakening Eta to a tropical depression by then.


Given these forecast updates:


*The Cayman Islands have already seen tropical storm conditions...conditions will quickly improve as Eta moves away


*Central Cuba will see strong tropical storm conditions tonight...time to prepare is over


*The western Bahamas will see tropical storm conditions by tomorrow morning...preparations must be finished tonight!


*Interests in south Florida and Florida Keys will see tropical storm or hurricane force conditions by tomorrow night and into Monday. Tomorrow is the last day to prepare! When in public...wearing a mask and frequent hand sanitizing will protect you from the COVID-19 virus. If you live in an area prone to coastal storm surge impacts...think of a family/friend residence or a hotel you can relocate to in case you may have to do so in the coming days...as a public storm shelter may not be as ideal in controlling your exposure to COVID-19.


*Interests in the northern Florida peninsula should gather storm preparation supplies early as Eta has a high chance of moving across the region as a tropical storm on Wednesday. This is to avoid last minute shopping crowds amid the COVID-19 outbreak. Also see previous bulletin for other advice related to preparing for Eta during the outbreak.


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

0 Hr Position (1800Z Nov 7)...60 mph maximum sustained wind tropical storm centered just north of the Cayman Islands at 20.4N-80.7W

IOH 24 Hr Forecast (1800Z Nov 8)...75 mph maximum sustained wind hurricane centered just west of Andros Island of the western Bahamas at 24N-79W

IOH 48 Hr Forecast (1800Z Nov 9)...75 mph maximum sustained wind hurricane centered over the southern Florida peninsula at 25.2N-80.5W

IOH 72 Hr Forecast (1800Z Nov 10)...75 mph maximum sustained wind hurricane centered over the eastern Gulf of Mexico at 26.5N-84.5W

IOH 96 Hr Forecast (1800Z Nov 11)...60 mph maximum sustained wind tropical storm centered offshore of the northwest Florida peninsula coast at 28N-84W

IOH 120 Hr Forecast (1800Z Nov 12)...35 mph maximum sustained wind tropical depression centered inland over the Florida/Georgia border at 30.5N-82.5W

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