Talking the Tropics w/ Mike: Isaac, Joyce & Caribbean/Gulf

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”:

* Major impacts from post-tropical Helene will continue for Georgia, Tennessee, the Carolina’s & parts of the Ohio Valley & Lower Mississippi Valley as the remnants produce heavy rain & major flooding while interacting with a large cut-off upper low.

* Isaac will stay far to the east & north over the open N. Atlantic

* Tropical storm “Joyce” over the E. Atlantic will not make it very far across the Atlantic.

* Eye on potential longer range tropical development over or near the Caribbean & Gulf of Mexico

The Atlantic Basin Overview:

(1) “Helene” -

As expected... “Helene” formed over the Northwest Caribbean... was upgraded to a tropical storm Tue. morning & a hurricane Wed. morning undergoing a rapid intensification cycle Thu. afternoon taking the hurricane to a Cat. 4 with a landfall about 11:10pm 10 miles W/SW of Perry in the Big Bend. The most U.S. hurricane landfalls in a season is 7 in 1886 followed by 6 in 2004 & 2020... the number stands at 4 through Sept., 2024.

According to Dr. Phil Klotzbach, Helene is the strongest hurricane to ever hit the Big Bend...the 4th Gulf Coast landfalling hurricane this year which has only happened 5 other times since 1851... lowest central pressure for a landfalling hurricane in Florida since Michael in 2018 (Cat. 5)... 9th strongest hurricane since 1900 to make landfall in Florida (based on sea level pressure).

A cut-off upper level trough has fully captured Helene’s remnants over the Tennessee & Ohio Valley’s. The combination of the stalled upper trough & remnants will continue to cause pockets of heavy rain though not to the extent of recent days.

Helene at the Big Bend was the 3rd (Idalia & Debby) hurricane landfall in the last 13 months - a very rare feat.

It was interesting - as I noted the past week - the rapid strengthening of hurricane “John” over the far East Pacific earlier in the week that moved inland on the west (Pacific side) coast of Mexico lastMon. night/early Tue. while Helene was just trying to get its act together. There may have been some symmetry with the Gulf system as upward vertical velocities that aided John spread eastward to the Atlantic Basin.

From tropical disturbance to a devastating Category 4 hurricane in two and a half days.

Hurricane Helene's incredible evolution from the Caribbean Sea to Florida coastline. pic.twitter.com/GMn8BLQmr4
— CIRA (@CIRA_CSU) September 27, 2024

5-day U.S. rainfall forecast (note increasing QPF over the Gulf where tropical development seems likely):

(2) “Isaac” formed Wed. evening, Sept. 25th over the North Atlantic & has become a hurricane but is no threat to land. 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.

(3) A strong tropical wave over the Eastern Atlantic was upgraded to tropical storm Joyce Fri. morning. The 10th Atlantic named storm develops on average Sept. 22. Joyce will not have a very long life span as hostile conditions will be encountered by Sunday over the Central Atlantic followed by dissipation by at least early to mid next week while turning sharply northward. No threat to any land areas.

Another tropical wave is following coming off the coast of Africa with potential development.

(4) Low pressure is again forecast to form over the Western Caribbean with potential tropical development in the longer term - roughly in the period Oct. 3 - 8th. For the moment - as one would expect beyond 5-7 days - forecast models are showing many mixed signals with poor consistency. The GFS is one of the more aggressive models bringing a landfall next weekend to the Gulf Coast... the European model is slower, weaker & farther south (had a slow, weak & west bias with Helene)... & the Canadian model is quite strong but slower & eventually more east. The Climavision ‘Horizon AI’ model is quite strong & points to the Big Bend (again!) by late in the weekend - the ‘Horizon’ was quite good with Helene.

Suffice to say at this point the area will need to be closely monitored.

Climavision’s HorizonAI Global Model (this model uses its own data & analysis for initialization of each model run + some AI input) valid for Sat. afternoon, Oct. 5 (trend is east & bit faster):

‘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 moving eastward & may be helping the active period of tropical activity across the Atlantic into 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: