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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.**********

...TUESDAY MAY 26 2020 1:42 AM EDT...

Even though the Atlantic hurricane season does not start until June 1...continuing daily birdseye view posts on the Atlantic tropics as I am monitoring two areas for potential tropical development (the National Hurricane Center this past afternoon introduced the area of interest just east of Florida into their tropical weather outlook)...see pair of area of interest sections below for additional details.

AREA OF INTEREST #1...The upper trough in the Gulf of Mexico continues drifting northward in a large scale stuck jet stream pattern...specifically in between a persistent upper trough regime over western North America and upper ridge over eastern North America and western edge of the Atlantic. The associated thunderstorm activity supported by the eastern divergence zone of this upper trough has likewise drifted northward while gaining concentration east of southeast Florida and over the northwestern Bahamas. The eastern divergence zone of this upper trough has also finally produced a surface trough of low pressure that streteches from the eastern Gulf of Mexico to the northwest Bahamas. ASCAT passes and radar animation have not so far yielded a closed circulation along the surface trough necessary for tropical cyclone formation...albeit radar animation earlier this evening seemed to briefly suggest an area of spin between Florida and the northwest Bahamas on the west edge of the concentrated thunderstorm activity. The surface trough disturbance is expected to continue tracking northward from the surface flow between western Atlantic surface ridging expected to persist beneath the convergence on the east side of the upper ridge axis and a broad area of frontal low pressure over the central United States to be supported by divergence on the east side of of the western North America upper trough. Because this disturbance will be largely tucked beneath the highly amplified upper ridge axis which would favor low shear and upper ouflow for additional support of thunderstorm activity...will be on the lookout for possible tropical cyclone development. In the updated outlook below...I have nudged odds of development upward with the thunderstorms gaining concentration further offshore of Florida...setting the stage for less land interaction as the disturance tracks toward the Carolinas. But I am keeping odds of tropical cyclone formation on the low side because a closed circulation is not yet defined.

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

IOH 24 Hr Outlook (0000Z May 27)...5% chance of tropical cyclone formation (offshore of the southeastern United States coast near 30N-80.5W)

IOH 48 Hr Outlook (0000Z May 28)...10% chance of tropical cyclone formation (coastal South Carolina near 33N-79.5W)

IOH 72 Hr Outlook (0000Z May 29)...0% chance of tropical cyclone formation (inland over the North Carolina/Virginia border near 36.5N-77.5W)

AREA OF INTEREST #2...A shortwave upper trough that was over the Great Lakes and southeastern Canada at this time yesterday has quickly shifted east-southeastward into the northwestern Atlantic while moving around a persistent longwave upper ridge over eastern North America. The eastern divergence zone of the upper trough is producing a small thunderstorm cluster north of Bermuda in the vicinity of 36.5N-65W. Over the next 72 models still insist that this shortwave upper trough will continue diving southeastward across the western Atlantic along the east side of the longwave upper ridge. On this dive...the shortwave upper trough has long been forecast by models to amplify into a cut-off upper vortex...producing a frontal low pressure system southeast of Bermuda where water temperatures are currently running at 24 to 26 deg or just below the threshold for tropical development. However the forecast cut-off upper vortex is expected to be cold enough where it can help boost thunderstorm activity...therefore the forecast frontal low pressure system could acquire tropical characteristics and become a subtropical cyclone. I have kept odds of subtropical development at 0% through 48 hours and begin rising odds above 0% at 72+ hours as this is when models generally agree that the surface frontal low pressure will develop. By 96+ hours...the longwave upper ridge over eastern North America is finally expected to shift eastward into the northwestern Atlantic...causing the cut-off upper vortex and surface frontal low pressure to drift northwestward and then northward around the southwest side of the upper ridge. I am keeping odds of subtropical development on the low side as models have trended weaker with the surface frontal low pressure...perhaps because the robust longwave upper ridge with its east convergence will maintain a strong surface ridge in the western Atlantic...perhaps strong enough to make it more difficult for a surface low pressure to take hold.

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

IOH 24 Hr Outlook (0000Z May 27)...0% chance of subtropical cyclone formation (east of Bermuda near 32.5N-62.5W)

IOH 48 Hr Outlook (0000Z May 28)...0% chance of subtropical cyclone formation (western Atlantic near 28N-55W)

IOH 72 Hr Outlook (0000Z May 29)...5% chance of subtropical cyclone formation (western Atlantic near 28N-57W)

IOH 96 Hr Outlook (0000Z May 30)...10% chance of subtropical cyclone formation (western Atlantic near 28N-59W)

IOH 120 Hr Outlook (0000Z May 31)...15% chance of subtropical cyclone formation (east of Bermuda near 32.5N-60W)

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