Talking the Tropics With Mike: Heads up Gulf Coast-what’s likely to be Helene develops in days ahead

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Tropics threats for Jacksonville/NE Florida/SE Georgia: None through the weekend into Tue./Wed. Given *current forecasts*, heavy rain, isolated tornadoes/waterspouts & rip currents at beaches will be a growing threat for NE Fl./SE Ga. Thu.-Fri. All areas from Texas to Florida need to stay up to date on the latest forecasts for mid to late parts of the upcoming week.

“Buresh Bottom Line”:

* The Caribbean & especially Gulf of Mexico remain an area where tropical development is likely over the next few days. This is a favored area for genesis later in Sept. & all forecast models are now onboard & indicate low pressure developing. While consistency amongst the models has been lacking during the past week, agreement has increased rather markedly during the last 24-36 hours or so. Don’t get caught up with unreliable sources & crazy postings on social media & elsewhere.

*** Everyone from Texas to Florida - but especially Louisiana to the Fl. Panhandle to the Florida west coast should prepare for impacts from what is likely to be “Helene”. ***

The Atlantic Basin Overview:

(1) All systems are “go” for low pressure to develop over the Northwest Caribbean & Southern Gulf of Mexico over the next few days. I’ve been hitting on this for more than a week but models have been all over the place on both location & intensity though finally coming into some semblance of agreement now. Given what looks like a more east development, the trek to land will be a shorter distance & therefore the timing has speeded up with potential landfall as early as Thursday, Sept. 26th.

Anyone with travel plans to - or who lives along - the Gulf Coast & west coast of Florida needs to pay attention to the latest forecast & would be wise now to begin preparations for a tropical cyclone.

The experimental ‘horizon’ forecast model by Climavision’s HorizonAI Global Model (this model uses its own data & analysis for initialization of each model run + some AI input) has at least been consistent in indicating tropical development - 3rd image below is for early midday Thu., Sept. 26. The model has recently trended faster & has become even stronger vs. previous model output (central pressure near 972mb/28.7″) & is pointing to a track into the Eastern Fl. Panhandle &/or Big Bend. Virtually all other global models are indicating development as well with relatively small - now - deviations in timing & track but still a pretty large range in intensity. The GFS has been & still is generally the most aggressive/strongest & farthest to the east - ‘Horizon’ model is similar - while the European operational model has recently become stronger & much farther east after being a west outlier & quite weak for most of the past week... the Canadian model is generally similar to the European - more west than the GFS & ‘Horizon’ & not as strong. Models have converged on a timing for landfall of Thu. afternoon/night/early Fri.

Any potential tropical system in this area should have at least some semblance of a northward movement thanks to general troughing aloft over the Lower 48 that gets reinforced in a few days. This is a climatologically favored area for tropical development later in Sept. & such systems are often steered northward by an ever more active, more meridional jet stream as we start to see the impacts of autumn weather patterns. The water, of course, is very warm & deep oceanic heat content is just about at its annual peak.

I suspect that low pressure/tropical development in this area will likely be gradual (festering) at first. Then once/if the energy can be “bundled”/organized, the disturbance *may* significantly increase in intensity. At the moment, there is a good deal of mid & upper level wind shear along with lots of dry air over & near the Gulf, but the atmosphere is forecast to undergo some modifications by midweek becoming potentially more conducive for a strengthening tropical system.

IF this system does indeed move into or very near the Big Bend, it would be the 3rd (Idalia & Debby) in the last 13 months - a very rare feat.

Anyone living along - or traveling to - the area from Texas to Florida needs to stay up to date on the latest forecasts.

(2) ‘The remnants of “Gordon” continue to languish over the Central Atlantic. There may some reorganization as the low turns more north then northeast & accelerates its forward speed under the influence of an upper level trough.

A tropical wave over the Eastern Atlantic has potential for gradual development but early indications are that the system would stay far out to the east over the open Atlantic.

Fitting the pattern for the increased tropical activity overall - as well as the wet/cloudy spell the first 2 weeks of September for Florida - is persistent & seasonally strong surface high pressure at northern latitudes from the Central U.S. to the Northwest Atlantic. This high pressure will bring has brought an early taste of fall across the Northern U.S. & generally encourages low pressure to the south - a pattern that often favors tropical development at southern latitudes. It’s Mother Nature’s constant balancing/compensating act. And it’s likely why we’ve seen forecast models struggle with the overall pattern developing sometimes spurious & frequent low pressure areas near & south of about 35 degrees N. It may also be why low pressure areas have a hard time “bundling” their energy - there’s just so much low pressure at lower latitudes competing for “space”.

I would be remiss if I did not mention some early striking similarities between the forecast development over the Gulf & hurricane Michael in 2018. I AM NOT SAYING the developing storm will be as intense but the storm during the upcoming week will be developing in a similar area, similar movement with influence from an upper level trough to the north... & forming quickly from next to nothing just a few days prior.

Keep in mind on the map below that the red shading is where a storm has the potential to develop & is not a track forecast:

Climavision’s HorizonAI Global Model for midday Thu., 09/26 (trend has been faster, more north & NE & strong [972mb/28.69″ in the case below):

The ultimate track of the *possible* storm will be dictated by an upper level trough that continues to get reinforced over the contiguous U.S. & any potential ridging underneath or on either side of the trough. Essentially - a stronger, deeper (more south) trough would allow for more north or even northeastward movement while a stronger ridge &/or weaker trough would allow the system to stay more west or perhaps even languish over the Gulf for a while.

500mb forecast from the GFS for Thu., 09/26. The upper level trough over the Central U.S. + positioning of a high pressure cell over the Western Atlantic & stronger ridge to the west will be key in where a Gulf tropical cyclone might track:

Mid & upper level wind shear is currently strong across the Gulf & Caribbean but is forecast to abate some over the next few days. Dry air over the Gulf is gradually moistening. And convection has increased a great deal over the Western Caribbean.

‘Velocity potential anomalies’ below still shows “sinking” air (brown lines) across the Atlantic Basin. In such a state, tropical development can occur but overall conditions are not as conducive as when there is overall rising (green lines) air such as much of the Pacific Basin where convection is active. This “pulse” of upward motion is moving eastward toward the Atlantic Basin & may help to be a cause for an uptick in Atlantic activity late this month 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..... “Helene” 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:

Sea surface temp. anomalies:

SE U.S. surface map:

Surface analysis centered on the tropical Atlantic:

Surface analysis of the Gulf:

Caribbean:

Atlantic Basin wave period forecast for 24, 48, 72 & 96 hours respectively:

East & Central Pacific:

Hawaii satellite imagery:

West Pacific:

Global tropical activity:

“Pulasan”:

“Soulik”: