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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.**********

...SATURDAY DECEMBER 21 2019 1:44 PM EDT...

Temporarily resuming birdseye view posts on the Atlantic tropics due to the feature mentioned in area of interest section below.

AREA OF INTEREST #1...In the Gulf of Mexico...a strengthening surface trough of low pressure with widespread cloudiness and rainfall extending into the southeastern United States is supported by widespread upper divergence ahead of an upper trough over the central United States. Over the next couple of days...warm deep-layered ridging to develop in warm air advection ahead of a strong frontal system moving into western North America will cause the adjacent central United States upper trough to amplify into an upper vortex moving across the southeastern United States...with strengthening divergence on the east side of the developing upper vortex causing the current Gulf of Mexico surface trough to intensify into a surface low pressure sliding across northern Florida and southern Georgia. This surface low will have a tight pressure gradient with respect to a surface ridge to the northeast supported by convergence on the back side of broad northwestern Atlantic upper although the surface low will not be acquiring tropical characteristics during this time heavy rainfall...coastal sea swells...and gusty winds are expected over parts of the southeastern United States from now through Monday. After that 72 to 96 hours...the upper vortex and surface low pressure is expected to shift east-southeast across the western Atlantic between the Bahamas and Bermuda due to the strength of the aforementioned warm deep-layered ridging over the United States. This is when I forecast some potential for this system to acquire some tropical characteristics with instability provided by 24 deg C waters and cold temperatures of the upper vortex. By 120 hours...the broad northwestern Atlantic upper troughing is forecast to amplify southward due to the strength of the ridging over the United States...which will allow it to absorb the upper vortex. This upper air pattern will result in increasingly unfavorable westerly wind shear across the western Atalntic as the upper vortex loses its defintion...and this is when I drop the odds of subtropical development down to 0%. Forecast positions in the outlook below are based on the upper divergence maximum of the developing upper vortex in the 1200Z GFS model run for the first 48 hours...followed by the forecast position of the upper vortex at 72+ hours.

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

IOH 24 Hr Outlook (1200Z Dec 22)...0% chance of subtropical cyclone formation (western Florida panhandle coast near 30.5N-87W)

IOH 48 Hr Outlook (1200Z Dec 23)...0% chance of subtropical cyclone formation (coastal Georgia near 31.5N-81.5W)

IOH 72 Hr Outlook (1200Z Dec 24)...10% chance of subtropical cyclone formation (offshore of the southeastern United States coast near 30.5N-76W)

IOH 96 Hr Outlook (1200Z Dec 25)...15% chance of subtropical cyclone formation (western Atlantic near 29N-70.5W)

IOH 120 Hr Outlook (1200Z Dec 26)...0% chance of subtropical cyclone formation (western Atlantic near 25.5N-61W)

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