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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.**********

...MONDAY AUGUST 21 2023 5:39 PM EDT...

Satellite image of the current eastern Atlantic tropical wave of low pressure being monitored for signs of development... image taken at 2040Z:

This special update is to primarily provide a track forecast and probabilities of tropical cyclone formation for the tropical wave of low pressure currently in the eastern Atlantic which was not included in previous full update #59... see area of interest #23 section below for more information. A short update to the surface trough of low pressure in the Gulf of Mexico is also provided... see area of interest #22 section below. For information on all other active tropical disturbances and cyclones in the Atlantic... refer to the full update from earlier this afternoon at the following link...

AREA OF INTEREST #22 (RECENTLY UPGRADED TO TROPICAL DEPRESSION NINE)... As of 5 PM EDT the organizing surface trough of low pressure in the Gulf of Mexico was assessed by the NHC to have strengthened further into tropical depression nine with 35 mph maximum sustained winds. Making no changes to my previous track and intensity projection... which brings the center of this system into southern Texas as a 60 mph maximum sustained wind tropical storm later tomorrow. Refer to full update #59 available at the following link for more information on this system and which land areas require preparation...

AREA OF INTEREST #23... The eastern Atlantic tropical wave of low pressure... whose north side recently passed over the Republic of Cabo Verde Islands... continues to display a broad area of rotation. The potential for tropical cyclone formation has clearly reduced in the short term as the rotation has lost much of its thunderstorm activity... with only some scattered activity in the northern part of this system. For now the rotation appears to be consolidating towards the northwest... near 16N-29W... based on the organization of what is left of the shower and thunderstorm activity... therefore the updated forecast track points shown below are adjusted in that direction. The westward forecast track has some northward angle overall as this system is forecast to move toward the surface ridge weakness caused by the remnants of Emily. By days 4 and 5 Emily and the western Atlantic frontal system/upper trough curving Emily northward are forecast to lift northeastward and away... around the amplified warm air mass upper ridge in the northwest Atlantic which will later progress toward the northeast Atlantic. However a northward angle in the forecast track is kept thru day 5 due to the likely influence of Franklin's surface circulation. Regarding odds of tropical cyclone formation... I have notably lowered short-term odds to 30% due to the above-mentioned reduction in thunderstorm activity and as the aforementioned warm air mass upper ridge pushes the south part of the current northeastern Atlantic upper trough toward this system by days 2 and 3... which will allow the southwest part of the upper trough to impart some northerly shear over this system. Noting that the northwestward adjusted forecast track points also are placing this system closer to this zone of shear. Atmospheric conditions are likely to improve for this tropical wave while it continues west-northwest away from the shear zone after day 3. Also computer models still try to develop this tropical wave in the longer range... and so my odds of tropical cyclone formation by day 5 are still above 50%... but lower than in previous full update #59 to account for the possibility that this system falls apart too much in the shorter-term northerly shear to be able to take advantage of the longer-term favorability.

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

IOH 24 Hr Outlook (1800Z Aug 22)... 30% chance of tropical cyclone formation (eastern tropical Atlantic near 17N-34W)

IOH 48 Hr Outlook (1800Z Aug 23)... 30% chance of tropical cyclone formation (eastern tropical Atlantic near 18N-39W)

IOH 72 Hr Outlook (1800Z Aug 24)... 30% chance of tropical cyclone formation (central tropical Atlantic near 19.5N-43W)

IOH 96 Hr Outlook (1800Z Aug 25)... 50% chance of tropical cyclone formation (central Atlantic near 20.5N-46W)

IOH 120 Hr Outlook (1800Z Aug 26)... 60% chance of tropical cyclone formation (central Atlantic near 21.5N-49W)

******National Hurricane Center ( official outlook as of 2 PM EDT*****************************

Formation chance through 48 hours...40%

Formation chance through 7 days (168 hours)...70%

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