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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.**********

...MONDAY SEPTEMBER 30 2019 6:04 PM EDT...

See Lorenzo section below for the only active tropical cyclone in the Atlantic basin. Elsewhere...a broad surface low pressure with thunderstorms is developing in the northwestern Caribbean the area of the Cayman Islands and Cuba...under supportive split upper-level flow as upper northerlies on the east side of the amplifying Gulf of Mexico upper ridge splits with upper southwesterly flow ahead of a western Atlantic upper trough and northwest side of western Atlantic upper ridge cell. Conditions for this disturbance to tropically develop could improve if the cold core western Atlantic upper trough...squeezed between the aformentioned warm core upper ridges and thunderstorm latent heat release...weakens and/or becomes split...therefore if this disturbance continues to have thunderstorm activity by tomorrow I will be considering it as an area of interest for tropical development. Meanwhile a tropical wave currently in the open central Atlantic well south of Hurricane Lorenzo...removed as an area of interest in post #140...has redeveloped thunderstorms thanks to upper outflow of an upper ridge cell...but will not likely develop as the unfavorable central Atlantic upper trough shifts southeastward toward this tropical wave. And finally the Euro (ECMWF) and NAVGEM models suggest the current tropical wave with thunderstorms over western Africa may develop an area of low pressure as it moves into the tropical Atlantic...and upper winds will become more favorable for development in the eastern Atlantic as the current unfavorable upper trough in the area is forecast to drift northward and away in upper southwesterly flow in the wake of upper troughing scheduled to transition Lorenzo into a non-tropical gale....waiting to see if the model support persists or increases before making this an area of interest for development on this blog.

HURRICANE LORENZO...Hurricane warning in effect for the Azores...preparations here for damaging winds and coastal sea swells should be finished by tomorrow morning as conditions will detereorate by tomorrow evening. Lorenzo's thunderstorm latent heat release and resulting warm core upper outflow appears to have kept the effects of a central Atlantic upper trough fragment to the west minimal...with the thunderstorms becoming more symmetric about the eye as the shear from the upper trough appears to have lessened. So although Lorenzo should continue to gradually weaken from the light shear and increasingly cooler waters along the forecast intensity forecast is slightly raised from my previous. Lorenzo is expected to turn increasingly eastward toward the Azores while moving northward past the Atlantic surface subtropical ridge...and coming under the influence of deep-layer southwesterly flow ahead of the currently developing northwest Atlantic frontal low and its upper trough. This upper trough will keep Lorenzo energized with tremendous upper divergence on its east side...thus transitioning Lorenzo into a formidable non-tropical remnant gale still packing hurricane-force winds...thus my intensity forecast shows only slow weakening. My updated forecast track is yet again nudged westward given Lorenzo's current position...and it appears the most significant effects from Lorenzo in the Azores will be towards the western islands.

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

0 Hr Position (1800Z Sep 30)...105 mph maximum sustained wind hurricane centered at 30.9N-42.1W

IOH 24 Hr Forecast (1800Z Oct 1)...95 mph maximum sustained wind hurricane transitioning to non-tropical centered southwest of the Azores at 36N-37W

IOH 48 Hr Forecast (1800Z Oct 2)...85 mph maximum sustained wind non-tropical remnant gale centered north of the Azores at 48.5N-25W

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