Talking the Tropics w/ Mike: Caribbean/Gulf poss development to be slow...Atlantic remains active

Jacksonville, Fl. — The “Buresh Bottom Line”: Always be prepared!.....First Alert Hurricane Preparation Guide... City of Jacksonville Preparedness Guide... Georgia Hurricane Guide.

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Tropics threats for Jacksonville/NE Florida/SE Georgia: None.

“Buresh Bottom Line”:

* Isaac staying far to the east & north over the open N. Atlantic & soon to become post-tropical

* “Joyce” over the Central Atlantic soon to dissipate.

* Eastern Atlantic depression will likely become a large & strong hurricane over the Eastern & Central Atlantic followed by another developing tropical cyclone.

* Eye on potential tropical development over or near the Caribbean & Gulf of Mexico during the upcoming week.

The Atlantic Basin Overview:

(1) Low pressure is again forecast to form over the Western Caribbean while moving northward over the Gulf of Mexico with potential tropical development in the longer term - roughly in the period Oct. 4 - 10th. Broad low pressure is already evident but any more concentrated low pressure would seem to be at least several days away.

For the moment - as one would expect beyond 5-7 days - forecast models are showing many mixed signals with poor consistency. As a whole... global models have recently trended generally trended weaker with a “north camp” & a “south camp”. BUT the models could always reverse this trend too, of course. The GFS had been one of the more aggressive models but is now showing a weaker landfall on the Gulf coast by early next week (was erratic but consistently strong w/ Helene)... the European model is slower, weaker & farther south (had a slow, weak & west bias with Helene) taking a system across Central Florida by early next week... & the Canadian model has trended south & generally weaker & similar to the European model. The Climavision ‘Horizon AI’ global model was quite strong & pointed to the Big Bend (again!) but has recently trended a bit south & definitely not as strong. The ‘Horizon’ was quite good with Helene. Overall - the global long range forecast models are showing more disorganized, at times multiple low pressures vs. a strong hurricane. But beware! - this could always change... & there is a pretty consistent signal for at least several days of heavy rain for Florida & nearby areas of the Southeast U.S. very late this week through the weekend into at least early next week.

Suffice to say at this point the area will need to be closely monitored. It does appear an upper level - 500mb - trough of low pressure diving down into the Eastern U.S. will have a lot to do with where the eventual possible Gulf low might go. A deeper trough will tend to draw any disturbance northward. However, if the trough axis is far enough east, the disturbance could get shunted more east before turning north or northeast. Bottom line is it’s still too early to determine exactly what will come of the eventual Gulf disturbance & where it might go.

Climavision’s HorizonAI Global Model (this model uses its own data & analysis for initialization of each model run + some AI input) valid for late Sat., Oct. 5 (trend is slower, a bit more south & weaker):

This is the ‘Horizon’ 500 mb (upper level) forecasts for early Mon., Oct 7th showing the digging trough into the Northeast U.S. with more of a “baggy” trough to the south interacting with a possible Gulf low. It’s possible the strong trough could miss the Gulf low complicating the ultimate track & intensity scenario even more.

7-day forecast rainfall:

(2) “Isaac” formed Wed. evening, Sept. 25th over the North Atlantic & became a hurricane but is moving over much cooler water while transitioning to a post-tropical low & strong ocean storm. The avg. date for the 9th named Atlantic storm is Sept. 16th... the avg. date for the 6th Atlantic hurricane of the season is not until Oct. 15th.

(4) Joyce formed Fri. morning. The 10th Atlantic named storm develops on average Sept. 22. Joyce will not have a very long life span & is about to dissipate over the Central Atlantic.

(5) Another strong tropical wave - ‘L-90′ was upgraded to tropical depression #12 Sunday afternoon & will soon be “Kirk”. Early indications are that #12 will become an intense hurricane but will not likely be able to make it across the Atlantic (should turn north over the Central Atlantic). Another strong tropical wave trails #12 & will likely develop. But the Bermuda High remains weaker & displaced to the east/northeast allowing for a nice & early alleyway over the Central Atlantic for which tropical systems can follow keeping them far from any land areas.

‘Velocity potential anomalies’ below shows far less “sinking” air (brown lines) across the Atlantic Basin. With sinking air, tropical development can occur but overall conditions are not as conducive as when there is overall rising (green lines) air where convection is active. This “pulse” of upward motion has moved eastward & appears to be helping the active period of tropical activity across the Atlantic that will continue into the first couple weeks of October.

REMEMBER WHEN A TROPICAL STORM OR HURRICANE IS APPROACHING: Taping windows is *not* recommended & will not keep glass from breaking. Instead close curtains & blinds.

Realize the forecast cone (”cone of uncertainty”) is the average forecast error over a given time - out to 5 days - & *does not* indicate the width of the storm &/or where damage might occur.

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

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

September tropical cyclone origins (early season breeding grounds are the Gulf &/or Western Caribbean:

Averages below based on climatology for the Atlantic Basin for September (2 hurricane so far, 3 tropical storms):

Wind shear (red - strong shear; green - low shear):

Saharan dust spreads west each year from Africa driven 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* interfere with 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 dust plume then try to develop if other conditions are favorable (we’ve already seen this with Beryl & Debby this year). In my personal opinion, there is way too much “hoopla” 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.

2024 names..... “Kirk” 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 (the last time this year’s list was used)... 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 because of the ‘04 season when Charley, Frances, Jeanne & Ivan - all retired names - hit Florida within a matter of about 6 weeks. 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 *.

Peak of the hurricane season Sept. 10th:

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 colors will brighten greatly as the water warms to greater depths deeper into the season: