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Since 2012 on the now retired Weather Underground 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 at Yale Climate Connections via Disqus where the former Weather Underground community has moved to. Feel free to reply to me there, at my Disqus feed at this link, or via e-mail at 

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*******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 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 dot gov) for the latest watches/warnings and official forecasts on active tropical cyclones.**********

...FRIDAY OCTOBER 23 2020 8:10 PM EDT...

Satellite image of western Caribbean Sea low pressure as of 2340Z:

Thunderstorms continue to become better organized on the east side of the large and broad surface low pressure field in the western Caribbean a location toward the Cayman Islands...Jamaica...and Cuba. Based on the organization shown in the lastest satellite imagery...I estimate that the lowest pressure of the disturbance is now just south of the Cayman Islands near 18N-80W and have begun a tropical cyclone formation forecast as outlined below. In the short-term over the next 48 hours...the approach of a shortwave upper trough from Texas and the rest of the broad surface low pressure area off to the west should push this system north across the Cayman Islands and toward western Cuba...and I forecast gradual strengthening to a tropical storm during this timeframe as the burst of shear from the shortwave upper trough should prevent rapid strengthening. At 72 hours once the shortwave upper trough passes by...this system will be left behind in a more favorable low shear and upper outflow environment beneath an expanding upper ridge over the western Caribbean...Gulf of Mexico...and eastern United States to be supported by warm air advection ahead of a vigorous frontal system to approach from the central and western US. Therefore by 72 and 96 hours I forecast intensification into a hurricane...but I do not show strength above category 1 as land interaction with western Cuba could become a slightly limiting factor. Models continue to trend with a narrower surface ridge weakness tied to the incoming frontal system from the central and western US...with surface ridges on either side of the front being more intact. This will result in a more westward angle in track as this system moves into the eastern Gulf of Mexico. By 120 hours weakening to a tropical storm is shown as the upper trough of the incoming frontal system will be likely imparting increasing wind shear...and the incoming front itself has potential to absorb this disturbance and make it less tropical in nature by that time or shortly thereafter. However even if this system loses tropical characteristics...there is longer term potential (just after 5 days) for this system to come ashore towards the Florida panhandle region as a vigorous frontal cyclone supported by the eastern divergence zone of the upper trough.

With these forecast updates...the potential for tropical storm conditions is increasing for the Cayman Islands this weekend. Tropical storm to hurricane force conditions are possible by this late weekend and into early next week for western Cuba and the Florida Keys. I recommend gathering storm preparation supplies early to avoid a last minute rush in crowded stores amid the COVID 19 virus outbreak...and when venturing out in public during preparation wearing a mask and frequent hand sanitizing will reduce your exposure to the virus. In case you may have to relocate from impacts such as coastal storm surge...think of a hotel or family/friend residence as a public shelter may not be as ideal for controlling your exposure to the COVID 19 virus. Interests along the US Gulf coast toward the Florida panhandle should also keep an eye on this system as it could bring high wind and coastal storm surge impact even as a vigorous non-tropical system

sometime next week. Forecast track below is nudged eastward from full update #158 due to the current estimated position using satellite pictures...and remains well east of global models like the GFS which I think are not picking up on the development at the east end of the broad surface low pressure...but instead try to gradually coalesce the whole low pressure at a location further west.

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

0 Hr Position (1800Z Oct 23)...Surface low centered just south of the Cayman Islands at 18N-80W

IOH 24 Hr Forecast (1800Z Oct 24)...45 mph maximum sustained wind tropical storm centered over the Cayman Islands at 19N-80W

IOH 48 Hr Forecast (1800Z Oct 25)...50 mph maximum sustained wind tropical storm centered between the Cayman Islands and Cuba near 20.5N-80.2W

IOH 72 Hr Forecast (1800Z Oct 26)...65 mph maximum sustains wind tropical storm centered just south of the western Cuba coast at 21.5N-81.5W

IOH 96 Hr Forecast (1800Z Oct 27)...85 mph maximum sustained wind hurricane centered just west of the Florida Keys at 24.5N-83W

IOH 120 Hr Forecast (1800Z Oct 28)...65 mph maximum sustained wind tropical storm centered over the northeastern Gulf of Mexico at 26.2N-85.2W

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