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Talking the Tropics w/ Mike: Helene goes Cat. 4 & takes aim at the Florida Big Bend

By Mike Buresh,

16 hours ago

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: Given *current forecasts*, some heavy rain, a few tornadoes/waterspouts, gusty winds & rip currents at area beaches will be a threat for NE Fl./SE Ga. through Thu. into early Fri. due to landfalling Helene a couple hundred miles west of Jacksonville. The exact magnitude of these impacts will ultimately depend on the exact track & strength of Helene. Right now - the I-75 corridor will have the highest winds in N. Central Florida.

All areas from Alabama to Florida need to stay up to date on the latest forecasts. Those in the Fl. Panhandle & west coast of Florida should complete hurricane preps. The peak time for impacts will be Thu.-Thu. night for Florida... Friday for Georgia & parts of the Carolina’s... even as far north as Tennessee.

“Buresh Bottom Line”:

* 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. Landfall looks to be this Thu. afternoon/evening near the Big Bend/Eastern Panhandle as a ‘major’ Cat. 3+ hurricane. Due to its swift movement, wind damage will occur well inland into at least Georgia & perhaps parts of the Western Carolina’s & as far north as Tennessee.

*** Do not get caught off guard & stay up to date on the latest forecasts. Everyone from Alabama to Florida - & especially the Fl. Panhandle to the Florida west coast into Georgia, Tennessee & the Western Carolina’s should prepare for major impacts from “Helene”. ***

IMPACTS FOR JACKSONVILLE/NE FLORIDA & SE GA.:

* The most significant impacts Thu. through Thu. night into early Fri. Expect rapidly improving weather conditions - but still breezy - through the day Friday. Forecasts *subject to change & updates!*

* WINDS - near/west of I-75 including Lake City, Fl. - sustained winds 50-70 mph, gusts 75-85+ mph... wind gusts 100+ mph near & to the immediate west of Columbia County.

I-75 to Highway 301: sustained winds 40 up to 50 mph, gusts 55-65+ mph

I-95 corridor: sustained winds 25-35 mph, gusts 45-55+ mph

Beaches, coast, intracoastal: sustained winds up to 50 mph, gusts 55-65+ mph

* STORM SURGE - SE Duval/St. Johns Co.: 1-3 feet...

NE Duval, Nassau, FL... Camden, Glynn, Ga: 2 - 3(+) feet.

St. Johns River: 1 -3 feet but higher values - up to 4 feet for downtown Jacksonville will be possible due to a period of strong winds from the south pushing water up & out of the riverbank late Thu. afternoon & night.

* TORNADOES & WATERSPOUTS - a few through Thursday night & there are indications of the potential for longer than average ground tracks - & intensity - by NE Fl./SE Ga. standards.

* RAINFALL : 2-4+ inches from Lake City, Fl. to Waycross, Ga.... 1-3 inches east of I-75 to Highway 301... 1-2 inches east of Highway 301 to the coast including most of Jacksonville/Duval Co.

The Atlantic Basin Overview:

(1) A Storm Surge WARNING: Mexico Beach eastward and southward to Flamingo ... Tampa Bay ... Charlotte Harbor

A Hurricane WARNING: Anclote River to Mexico Beach

A Hurricane WATCH: Englewood to Anclote River, including Tampa Bay

A Tropical Storm WARNING: Florida Keys, including the Dry Tortugas ... Flamingo to Anclote River, including Tampa Bay ... West of Mexico Beach to the Okaloosa/Walton County Line ... Flamingo northward to Little River Inlet ... Lake Okeechobee ... Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth.

Landfall - Thursday, Sept. 26th in the late evening between approximately 9pm & midnight EDT & will be the 4th U.S. landfalling hurricane of the season. The turn north/NE has occurred with an increase in forward speed to above 20 mph accompanied by a period of rapid intensification (RI).

No travel is recommended into Fri. over NW Florida, the Eastern Pahandle & parts of Georgia.

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 - 9 & 10th image below is for 8pm Thu., Sept. 26 & 2am Fri., Sept. 27th. The model is pointing to a track into the Big Bend of Florida with a landfalling hurricane that is moving quickly to the northeast turning a little more northward further inland. Virtually all other global models are indicating similar movement & landfall. Eyewall replacement cycles & other structural nuances may dictate intensity as Helene approaches land but it’s clear Helene will be a powerful hurricane while moving inland.

The trek northward is being caused by general troughing aloft over the Lower 48 that is being strengthened by a deep upper level disturbance dropping southward into the heart of the U.S. that will then cut off from jet stream while capturing Helene. The depth & exact position of this trough is key to how sharp the northward movement of Helene is as well as a gradual bend more northwest once inland due to interaction with the upper level trough (the trough draws Helene N/NW then northwest before stalling & weakening further over the Tennessee Valley once in the “belly” of the upper trough). The combination of the stalled upper trough & then Helene remnants will result in an extreme rainfall event for parts of the Tennessee Valley, Lower Ohio Valley & Southern Appalachians.

The Caribbean & Gulf are a climatologically favored area for tropical development later in Sept./Oct. & 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.

Warm ocean water - near the surface as well as to deep depths, & high atmospheric humidity all point to favorable conditions for Helene. In addition, the nearby upper level trough to the north over the Lower 48 will aid ventilation over the top of Helene with shear vectors - though modestly high - in roughly the same direction as the forward movement - both can aid to intensify tropical cyclones which may occur right up to landfall barring eyewall replacement cycles. The underside of Helene should quickly dry out at & beyond landfall leaving a heavily weighted north side storm as Helene moves swiftly inland & gradually decays while rotating dry continental air into its counterclockwise circulation.

Helene in or very near the Big Bend, will go down as the 3rd (Idalia & Debby) hurricane landfall in the last 13 months - a very rare feat.

Anyone living along - or traveling to - the area from Alabama to Florida northward to the Tennessee Valley & Western Carolina’s needs to stay up to date on the latest forecasts.

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 Helene 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.

It’s also interesting to note the rapid strengthening of hurricane “John” over the far East Pacific that moved inland on the west (Pacific side) coast of Mexico Mon. night/early Tue. There may be some symmetry with the Gulf system as upward vertical velocities that aided John spread eastward to the Atlantic Basin.

Keep in mind impacts from the storm will extend well beyond the center AND the cone. Do not fixate on the cone or a perceived center point. Remember that a skinny cone simply means a higher confidence forecast & that dangerous weather conditions will extend way beyond the cone:

Storm surge forecast map:

Climavision’s HorizonAI Global Model late Thu., 09/26 for 8pm & 2am EDT Fri., 09/27 respectively (pretty steady trend & track - near 955mb/28.00-28.15″) showing landfall 10pm - midnight Thu. with a fast moving, powerful tropical cyclone well inland into & through Georgia. This model is a tad east of the official NHC forecast & some other global models, especially after landfall:

500mb forecast from the GFS for Thu. 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 across the Gulf & Caribbean increases again over the Central & Northern Gulf. But the shear vectors will not be overly hostile since Helene will be moving N/NE. There will be impressive shear magnitudes at low & mid levels unfortunately helping the potential spin in the atmosphere for tornadoes. The 2nd image is deep oceanic heat content (OHC) + shear.

Radar imagery from South Fl. Water Management District (solid line is ‘Helene’ forecast track previous advisory vs. latest NHC advisory:

Tallahassee N.W.S. doppler radar:

Tampa N.W.S. radar:

Jacksonville N.W.S. radar:

Jacksonville/NE Fl./SE Ga. rainfall courtesy GFS & European models:

Heavy rain is forecast along much of the Gulf coast. While it’s recently been drier for NE Fl. & SE Ga., a lot of water remains “in the system” so flooding will be a concern by Thu./Fri.:

(2) Tropical storm “Isaac” formed Wed. evening over the North Atlantic but will move eastward over the open Atlantic - no threat to land.

(3) A strong tropical wave over the Eastern Atlantic will move northwest & has a good chance to develop but appears destined to stay far out to sea. Another tropical wave is following coming off the coast of Africa.

I am also keeping a close on eye on the Caribbean &/or Gulf of Mexico (again!) for potential tropical development roughly in the period Oct. 5 - 10th.

‘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 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 over the next few weeks.

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..... “Joyce” 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: