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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 forecast 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 MAY 25 2024 10:40 AM EDT...

The following is a special update on the surface low pressure area that has moved from the eastern Bahamas and into the western Atlantic waters south of Bermuda over the last 36 hours... tagged as area of interest #2 in previous full update #3.

Satellite imagery of the western Atlantic surface low pressure area now passing south of Bermuda covering the last several hours (left image from 1810Z May 24 and right image from 1400Z today... red L marks the position of the surface low pressure area in each image):

The surface trough of low pressure that was over eastern Cuba and eastern Bahamas early on Friday has since accelerated northeastward into the western Atlantic waters south of Bermuda while following the supportive divergence zone of a northeastward-moving fragment of its parent upper trough. The divergence zone appeared to be focused enough to allow the surface trough to develop a more concentrated spin more resembling a surface low pressure center... however by the time this occurred this system was moving into cooler waters below 26 deg C (also the parent upper trough fragment is too warm... 200 mb heights well above 1200 dekameters... to support instability over waters below 26 deg C). Therefore the thunderstorm activity never gained much concentration near the surface low pressure center... and this system has been dropped from the NHC tropical weather outlook as tropical cyclone formation is no longer anticipated.

Long-term outlook: Westerly shear is expected to increase... making conditions further hostile for tropical development... as the southern base of an upper trough from eastern Canada and associated upper westerlies overspread this system. In addition a shearing upper trough fragment that has recently ejected from the current central North America weather system has quickly pivoted into the eastern US and will soon be chasing this system. The upper trough fragment from the eastern US... major upper trough from eastern Canada... and parent upper trough fragment of this system are expected to merge while moving eastward into the open central Atlantic and toward the Azores. While reaching this position the merged upper trough is expected to amplify into a cold cut-off upper vortex due to adjacent amplification of upstream upper ridging induced by the warm sector of what is currently the vigorous central North America frontal system/upper trough. What happens long-term to the remnant surface low pressure of this system depends on its position relative to the forecast cold-core cut-off upper vortex... if it ends up on the southwest side as the recent model consensus suggests it will dissipate in the upper convergence in that quadrant of the upper vortex while the divergent east side of the upper vortex produces a new surface cyclone. If it aligns with the eastern divergence zone of the upper vortex then the remnant surface low pressure will simply re-intensify as a surface cyclone. Either way the long-term forecast surface cyclone may have the instability profile it needs for tropical development should it be parked over warm enough waters (around a mild 20+ deg C)... due to the cold de-stabilizing temperatures of the upper vortex. For now the model consensus is trending further north with the upper vortex and surface cyclone... over even cooler waters in the teens of deg C... where tropical development would be unlikely.

Currently this will be my last update on the Atlantic tropics until the start of the 2024 Atlantic Hurricane Season in June. Should the forecast regarding the aforementioned upper vortex and surface cyclone trend back further south over warmer waters... may re-issue daily updates on the Atlantic tropics before then.

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