Talking the Tropics With Mike: Sean soon to dissipate followed by likely Tammy

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*** LOCAL (Jacksonville/NE Fl./SE Ga.) IMPACTS FROM THE TROPICS: None.

The Atlantic Basin Overview:

** “Sean” is over the Central Atlantic...

** A strong tropical wave is over the Eastern Atlantic...

(1) wave ‘92-L’ over the Eastern Atlantic was upgraded to tropical depression #19 Tue. evening & to tropical storm “Sean” early Wed. before being downgraded back to a depression Wed. evening then back to a weak tropical storm Thu. morning... & finally back down to a depression late Sat. Sean will continue to battle persistent wind shear & is likely to eventually dissipate over the Central Atlantic soon. There’s some indication that the remnants of Sean could be swallowed up by a nontropical midlatitude cyclone by Fri./Sat. near the U.S. east coast/W. Atlantic.

(2) A tropical wave - ‘94-L’ - at a lower latitude & to the southeast of Sean is likely to develop further (into “Tammy”). Forecast models are slowly coming into better agreement with the eventual outcome, but the GFS still turns the disturbance northward earlier (faster to deepen) vs. the European model which is slower to develop a stronger/deeper tropical cyclone thereby later in turning north with the potential for impacts on the Northeast Caribbean approximately next weekend. The ultimate outcome should be tied to just how strong this wave becomes & when - but a wave to watch no doubt.

Troughing remains prevalent over the Eastern U.S./Western Atlantic which should protect the U.S. east coast from any direct impacts.

‘94-L’:

Sean:

The upper oceanic heat content (UOHC) [tropical cyclone heat potential/TCHP] across the SW Atlantic, Gulf & Caribbean:

Water vapor loop (dark blue/yellow is dry mid & upper level air):

October tropical cyclone origins:

Averages below based on climatology for the Atlantic Basin for October:

Wind shear:

Saharan dust spreads west each year from Africa by the prevailing winds (from east to west over the Atlantic). Dry air - yellow/orange/red/pink. Widespread dust is indicative of dry air that can impede the development of tropical cyclones. However, sometimes “wanna’ be” waves will just wait until they get to the other side of - or away from - the plume then try to develop if other conditions are favorable. In my personal opinion, way too much is made about the presence of Saharan dust & how it relates to tropical cyclones. In any case, the peak of Saharan dust typically is in June & July.

2023 names..... “Tammy” is the next name on the Atlantic list (names are picked at random by the World Meteorological Organization... repeat every 6 years). Historic storms are retired [Florence & Michael in ’18... Dorian in ’19 & Laura, Eta & Iota in ‘20, Ida in ‘21 & Fiona & Ian in ‘22]). In fact, this year’s list of names is rather infamous with “Katrina”, “Rita” & “Wilma” retired from the ‘05 list & “Harvey”, “Irma”,“Maria” & “Nate” from the ‘17 list. The WMO decided - beginning in 2021 - that the Greek alphabet will be no longer used & instead there will be a supplemental list of names if the first list is exhausted (has only happened three times - 2005, 2020 & 2021). The naming of tropical cyclones began on a consistent basis in 1953. More on the history of naming tropical cyclones * here *.

East Atlantic:

Mid & upper level wind shear (enemy of tropical cyclones) analysis (CIMMS). The red lines indicate strong shear:

Water vapor imagery (dark blue indicates dry air):

Deep oceanic heat content over the Gulf, Caribbean & deep tropical Atlantic. The brighter colors are expanding dramatically as we near the peak of the hurricane season.: