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BIRDSEYE VIEW POSTS

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 IOHurricanes@outlook.com 

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MY 2023 ATLANTIC HURRICANE SEASON BIRDSEYE VIEW POST #56A (Special Update)

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


...FRIDAY AUGUST 18 2023 12:12 PM EDT...

Satellite image of tropical waves currently spanning the eastern and central tropical Atlantic as of 1200Z today:

This special update is to provide a track forecast and probabilities of tropical cyclone formation for the tropical wave of low pressure currently approaching the Lesser Antilles from the central Atlantic which was not included in previous full update #56... see area of interest #24 section below for more information. A short update to the tropical wave currently west of the Repbulic of Cabo Verde Islands is also provided... see area of interest #21 section below.


AREA OF INTEREST #20... No changes since previous update... refer to previous update at the following link... https://www.infohurricanes.com/post/my-2023-atlantic-hurricane-season-birdseye-view-post-56


AREA OF INTEREST #21... The tropical wave of low pressure in the eastern Atlantic... currently west of the Republic of Cabo Verde Islands... has become better organized with increased thunderstorm activity. In this special update I am increasing short-term odds of tropical cyclone formation to 40%... before the tropical wave later encounters less favorable westerly shear and dry Saharan air lurking to the north. Refer to the previous update at the following link for more information on this tropical wave... https://www.infohurricanes.com/post/my-2023-atlantic-hurricane-season-birdseye-view-post-56


AREA OF INTEREST #22... No changes since previous update... refer to previous update at the following link... https://www.infohurricanes.com/post/my-2023-atlantic-hurricane-season-birdseye-view-post-56


AREA OF INTEREST #23... No changes since previous update... refer to previous update at the following link... https://www.infohurricanes.com/post/my-2023-atlantic-hurricane-season-birdseye-view-post-56


AREA OF INTEREST #24... A tropical wave of low pressure with rotating shower and thunderstorm activity was positioned near 10.5N-55W as of 1200Z. After crossing Lesser Antilles islands over the next 24 hours... this tropical wave has an opportunity to interact with a pair of upper anticyclones with supporting low shear and upper outflow as follows:


(1) The current Caribbean upper vorticity will retorgrade westward and away while pushed around Gulf of Mexico upper ridge and later a building central US upper ridge... giving way to an expanding upper anticyclone over the Caribbean.


(2) The southern vorticity of the current eastern Canada to eastern US upper trough is forecast to retrograde southwestward and away around an upper ridge that later builds over the central US. This will allow for another anticyclone to build in the western Atlantic to the north of Puerto Rico... in between an ongoing western Atlantic upper vortex and the retrograding upper vorticity.


Recent model runs are split on which anticyclone could contribute to this tropical wave's development. More southwestern solutions such as yesterday's 1200Z CMC and NAVGEM develop the wave under the Caribbean anticyclone while more northeastern solutions such as today's 1200Z GFS suggest the northeastern part of the wave takes a more northern track while becoming entangled with area of interest #20 and the surface ridge weakness that will be induced by the western Atlantic upper vortex... potentially allowing the northeastern part of the wave to potentially develop just north of Puerto Rico and underneath the western Atlantic anticyclone. By day 5 my forecast position shown below splits the difference between the northeastern and southwestern solutions. I have set odds of tropical cyclone formation to a low 10% as all of the above mentioned influences may simply cause this tropical wave to degenerate into an elongated southwest-northeast surface trough spanning from the central Caribbean to the waters north of Puerto Rico by day 5.

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

IOH 24 Hr Outlook (1200Z Aug 19)... 0% chance of tropical cyclone formation (just east of the southern Lesser Antilles near 11N-60W)

IOH 48 Hr Outlook (1200Z Aug 20)... 10% chance of tropical cyclone formation (southeastern Caribbean Sea near 12N-65W)

IOH 72 Hr Outlook (1200Z Aug 21)... 10% chance of tropical cyclone formation (eastern Caribbean near 14N-69W)

IOH 96 Hr Outlook (1200Z Aug 22)... 10% chance of tropical cyclone formation (north-central Caribbean near 16N-72W)

IOH 120 Hr Outlook (1200Z Aug 23)... 10% chance of tropical cyclone formation (just southeast of Jamaica near 17N-75W)

******National Hurricane Center (hurricanes.gov) official outlook as of 8 AM EDT*****************************

Formation chance through 48 hours...10%

Formation chance through 7 days (168 hours)...30%

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