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 

  • NCHurricane2009


*******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.**********

...UPDATE...MONDAY AUGUST 9 2021 3:55 PM EDT...

Based on the latest satellite imagery...tropical low pressure Invest 94-L closing in on the Lesser Antilles will also have potential to produce heavy rains and gusty winds further north...across Dominica and addition to Barbados... Grenada... St Vincent and the Grenadines... St Lucia... and Martinique. See the update from 10:40 AM EDT below for more information on 94-L.

...MONDAY AUGUST 9 2021 10:40 AM EDT...

The following is a special update on events with the pair of central Atlantic tropical surface low pressures approaching the Caribbean Sea:

(1) Tropical Low Pressure Invest 93-L has seen a significant decrease in thunderstorms likely due to dry saharan air to the northeast and is less likely to develop as it moves toward the northern Lesser Antilles... Virgin Islands... Puerto Rico... Haiti... and the Dominican Republic in the coming days. I will have an updated outlook with lower odds of development in my next full update later today.

(2) Attention has become focused on Tropical Low Pressure Invest 94-L which has seen an increase in organized thunderstorm activity over the last few hours. Regardless of tropical cyclone formation or not in the short-term...expect heavy rains with potentially gusty winds to overspread the following Lesser Antilles Islands later today: Barbados... Grenada... St Vincent and the Grenadines... St Lucia... and Martinique.

(3) I have provided an update to my outlook on Invest 94-L outlined agreement with the NHC on raising odds of development to a high 70%. For the next 6 hours...I forecast a 50% chance of tropical cyclone formation as Invest 94-L moves over the southern Lesser Antilles islands mentioned above... which is higher than my outlook from full update #74 from last evening. My updated forecast track allows for a little more northward angle as the weakening of 93-L would allow for reduced fujiwhara influence from that feature. However based on the latest satellite loops...94-L is still retaining a strictly due west heading and therefore my updated forecast track is still south of the NHC outlook guidance and model guidance...which would keep the risk lower for the Virgin Islands... Puerto Rico... Haiti... and the Dominican Republic. By the end of the five day forecast period...the north angle in track is likely to increase as a large frontal cyclone over North America is forecast to weaken the west extent of the steering Atlantic surface ridge... and also as some of the current western Atlantic upper vorticity string is forecast to linger near Florida and the eastern Gulf of Mexico which would also pull this system north especially if it develops a stronger/taller structure more coupled to upper-level winds. Therefore interests in Jamaica... the Cayman Islands... and Cuba should monitor the progress of this system for potential impacts in the 4 to 6 day window.

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

IOH 6 Hr Outlook (1800Z Aug 9)...50% chance of tropical cyclone formation (near Barbados at 13N-60W)

IOH 24 Hr Outlook (1200Z Aug 10)...70% chance of tropical cyclone formation (eastern Caribbean Sea near 13.5N-64W)

IOH 48 Hr Outlook (1200Z Aug 11)...70% chance of tropical cyclone formation (central Caribbean Sea near 14N-69W)

IOH 72 Hr Outlook (1200Z Aug 12)...70% chance of tropical cyclone formation (central Caribbean Sea near 15N-74W)

IOH 96 Hr Outlook (1200Z Aug 13)...70% chance of tropical cyclone formation (just southwest of Jamaica near 16.5N-78.5W)

IOH 120 Hr Outlook (1200Z Aug 14)...70% chance of tropical cyclone formation (just west of the Cayman Islands and south of western cuba near 19.5N-82.5W)

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