Talking the Tropics w/ Mike: Gulf development may impact Fl. next week.. twin hurricanes Kirk,Leslie

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

“Buresh Bottom Line”:

* “Kirk” & “Leslie” over the far Eastern Atlantic.

* Wary eye on potential tropical development over the Gulf of Mexico over the next few days with *possible* impacts on especially West & Southwest Florida. Regardless of tropical development, there is a very heavy rain threat for much of Florida over the next 5-7 days.

* “The Hell that was Helene” - Buresh Blog.

The Atlantic Basin Overview:

(1) Weak low pressure continues to be likely to develop over the Gulf of Mexico with potential gradual tropical development late this weekend into next week.

Forecast models are arduously coming into some very general agreement on low pressure over the Gulf of Mexico next week. Heads up for Florida - especially the W/SW coast by the middle of next week. Virtually all of the forecast models have trended more north & at least somewhat stronger though significant run to run inconsistencies continue - not surprising given low pressure has truly organized. The Climavision ‘Horizon AI’ global model initiated the trend late Thu. to stronger & more north with a fairly strong tropical cyclone approaching Tampa Bay by Wed. The ‘Horizon’ was quite good with Helene.

Overall - the global long range forecast models seem to be battling broad low pressure at lower latitudes & have been developing multiple low pressures that struggle to organize. But we may now be on to something nearing the west &/or SW coast of Fl. Tue.-Wed. But beware! - this set-up remains in flux... AND there is a pretty consistent signal for at least several days of heavy rain & potentially significant flooding for parts of Florida this weekend into next week. Expect specific forecast details to ebb & flow in the coming days until a decent core potentially develops. We are also seeing signs of low pressure developing east of Florida near the Bahamas over the next few days which could complicate Gulf development.

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. Confluent upper level flow on the backside of the trough should continue at least some shear near Florida as well as a vector pointing SE - both of which could be factors in how a tropical cyclone might develop & move. Bottom line is it’s still too early to determine exactly what exactly will come of the eventual Gulf low & where it might go. But heads-up Florida!

Climavision’s HorizonAI Global Model (this model uses its own data & analysis for initialization of each model run + some AI input) valid for early Wed., Oct. 9 shows a 988mb/29.20″ tropical cyclone west of Tampa Bay moving E/NE:

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. This trough will impart some shear over/near Florida as well as a tendency to suppress some any low - more to the south (vs. Gulf Coast).

GFS 500mb forecast for this Sunday. The persistent alleyway over the Central Atlantic looks like it stay intact effectively protecting the U.S. & Caribbean from Kirk & Leslie over the Eastern Atlantic:

7-day forecast rainfall:

(2) “Kirk” has quickly strengthened over the Eastern Atlantic. Kirk became a hurricane Tue., the 7th of the Atlantic season which does not occur until Nov. 15th in an “average” season... & became a ‘major’ Cat. 3+ hurricane Thu. Kirk is already northward & will stay far away from the Caribbean or U.S. & far to the east of Bermuda. The Bermuda High remains weaker & displaced to the east/northeast allowing for a nice & early alleyway over the Central Atlantic which Eastern Atlantic tropical systems can follow keeping them far from any land areas & certainly well east of the Caribbean & U.S. The average date for the 11th named storm is Sept. 14th so nothing at all unusual right now vs. climatology when it comes to named storms vs. the avg. Atlantic hurricane season.

(3) Tropical depression #13 has formed right behind - to the east of - & was upgraded to “Leslie” Wed. night & became a hurricane Fri. evening - the 8th of the Atlantic season & now exceeds the avg. for the entire season of 7 hurricanes. Like Kirk, sister Leslie will stay well out to the east over the Central & Eastern Atlantic. The 12th named storm develops - on avg. - Oct. 11th.

Due to the intensity of the two storms, an easterly swell will emanate far to the west reaching the east coast this weekend into next week enhancing the rip current risk at beaches along the east coast, Bermuda & the Caribbean.

‘Velocity potential anomalies’ below shows far less “sinking” air (brown lines) spreading across the Pacific 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 & likely helped Helene & other Atlantic tropical cyclones & is past its peak. The low over the Gulf of Mexico will have to battle the less favorable vertical velocity environment.

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):

October tropical cyclone origins:

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

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..... “Milton” 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 *.

Through Oct. 1 courtesy Dr. Phil Klotzbach:

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: