Talking the Tropics With Mike: Weakening Francine... t.d. #7 E. Atlantic... eye on SW Atlantic low

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Tropics threats for Jacksonville/NE Florida/SE Georgia: No direct impacts from tropical systems *but* onshore flow has increased again with rough seas & surf = a high rip current risk into the weekend. The heavy rainfall & flooding threat remains through at least Friday with some extra tropical moisture courtesy the circulation around distant Francine & its remnants.

“Buresh Bottom Line”:

* “Francine” is moving inland over Louisiana & weakening. Heavy rain & a threat for tornadoes will extend well inland in Louisiana, Mississippi & Alabama as far north as Arkansas, Tennessee & Kentucky & as far east as the Florida Panhandle through Thu. night & - in some cases - into Friday.

* A couple of tropical waves over the Central & Eastern Atlantic + tropical depression #7 - soon to be “Gordon” but look to stay far out to sea.

* Low pressure is expected to develop east/northeast of Florida & near/just north of the Bahamas over the weekend then move north/NW possibly becoming a tropical cyclone on its way to or near the N. Carolina coast by Mon./Tue. Heads up from the Carolina’s to Chesapeake Bay & nearby areas. The upshot for Jacksonville/NE Fl./SE Ga. will be drier air working southward along the backside that should finally give the local area a chance to dry out somewhat.

The Atlantic Basin Overview:

A Storm Surge WARNING: Avery Island Louisiana to the Mississippi/Alabama Border ... Vermilion Bay ... Lake Maurepas ... Lake Pontchartrain

A Tropical Storm WARNING: Intracoastal City, Louisiana to the Alabama/Florida border ... Lake Maurepas and Lake Pontchartrain, including metropolitan New Orleans.

(1) ‘91-L′ - “Potential Tropical Cyclone Six” was upgraded to tropical storm “Francine” Mon. morning becoming a hurricane Tue. evening then made landfall near 6pm EDT as a Cat. 2 - 100 mph hurricane about 30 miles S/SW of Morgan City & about 90-100 miles west/southwest of New Orleans before being downgraded to a tropical storm late Wed. evening just west of New Orleans. Francine was a product of the Caribbean wave I’ve been tracking for the past 7+ days reached the Yucatan Peninsula Friday & moved over the Bay of Campeche over the weekend merging with low pressure that dropped south from Texas.

Francine came ashore as a Cat. 2 after a burst of organization & convection late Wed. afternoon & is turning northward & slowing down while weakening. Weak to moderate upper level troughing persists over the Central & Eastern U.S. helping to create the alleyway for Francine. Dry air quickly ate away the underside (south) of the circulation while moving inland. Francine’s remnants will stall over the Tennessee Valley as the surface feature dissipates but the upper level “energy” (disturbance) will then drift southeast helping to enhance t’storms over much of the Southeast through Friday.

For the Atlantic: the sixth named - ‘F’ - storm of the season avg. date is Aug. 29th... the 4th hurricane avg. date is Sept. 16th.

(2) The next area to keep a watch - as far as possible land impacts - is the Southwest Atlantic. Virtually all models now develop low pressure east of Florida over the weekend that moves north then bends back some to the northwest. Such a track puts the Carolina’s on alert for a *possible* tropical system by Mon. into Tue. with impacts extending northward to at least Chesapeake Bay. The Climavision ‘Horizon’ model (see maps further down) has indicated this potential for several days & is locked in on a tropical storm landfall on the Central & Northern North Carolina coast Monday morning. Some other models are a little slower & have recently trended a little weaker but there is general agreement. Heads-up U.S. east coast!

(3) Multiple tropical waves are moving west & northwest between the Caribbean & Africa - something one would expect this time of year. At least one - ‘92-L’ is losing its longer term potential while a stronger tropical wave - ‘93-L’ to its east was upgraded Wed. morning to tropical depression #7. #7 is likely to become at least a tropical storm if not a hurricane but is also likely to stay far to the east over the Atlantic. The Bermuda high remains displaced to the east & northeast over the Atlantic. Such a position favors an alleyway for systems to turn north over the Central Atlantic... at least over the next 10-12 days or so.

Fitting the pattern for the increased tropical activity - as well as the recent wet/cloudy spell 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.

From CIMSS - diagnosis below of shear shows strengthening values over the northern half of the Gulf which should help spread tropical moisture downwind all the way to Florida increasing the heavy rain potential while imparting a good deal of left to right shear on Francine:

Francine’s heavy rain & flooding threat north all the way to Memphis, Paducah & Evansville. Very heavy rain for much of the Gulf coast yet again for the next few days:

Climavision ‘Horizon’ model showing low pressure developing east of Florida then moving N/NW as strengthening tropical storm:

‘Velocity potential anomalies’ below shows “sinking” air (brown lines) across the Atlantic Basin gradually breaking down. 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 & is likely aiding “Francine” as well as future systems over the next 1-2 weeks.

Historical Note: 60 years ago - Cat. 2 hurricane “Dora” made landfall in St. Johns Co. north of St. Augustine just after midnight Sept. 10, 1964. Then President Lyndon B. Johnson visited Jacksonville Beach declaring NE Fl. a national disaster area... while the Beatles still played in Jax. Florida Times-Union report & photos * here *. Dora is the last hurricane eye to make landfall on the Northeast Florida coast.

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..... “Gordon” 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:

“Bebinca” is expected to become a typhoon while moving across some Japanese islands distant southwest of the mainland then into China: