Talking the Tropics With Mike: Florence slowly winding down but still dumping torrential rain

Sept. 16, 2018 — The "Buresh Bottom Line": Always be prepared!.....First Alert Hurricane Survival Guide... City of Jacksonville Preparedness Guide... Georgia Hurricane Guide.  

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FLORENCE - landfall - as Cat. 1 - early Fri.... edge of eyewall at 6am... center of the eye at 7:15am EDT at Wrightsville Beach, NC very near Wilmington..... moving ever so slowly westward & weakening to a tropical depression



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Rainfall estimated by Doppler Radar through early Sunday:

"Florence"  - a named storm for the 14th straight day Fri. - became the 3rd hurricane, 1st "major" of the '18 Atlantic season Tue.... went Cat. 3 then briefly Cat. 4 last Wed. ...  fell apart in the face of shear & dry air Thu.... continues moving into the Western Atlantic & made the expected comeback reaching Cat. 4 strength again Mon.  The tropical cyclone made the important turn northwest reaching Jacksonville's latitude BUT hundreds (400+) of miles to the east - late Wed./Wed. night.  Florence went through some serious structural alterations Wed. probably due to nearby dry air & some shear which has caused weakening & never could fully recover. Florence made landfall early Friday as a Cat. 1 & the underside (south portion) of the circulation is pretty quickly weakening while the north & east quadrants remain relatively strong.  Such an evolution is not uncommon with landfalling tropical cyclones as dry air is often first ingested from the west due to the counter-clockwise circulation.

Despite the general weakening the last couple days, Florence has been - & will be - a big hit on the Carolina's:  Major to severe impacts can be expected & - in some instances - truly catastrophic. Very heavy rain has - & will - cause widespread flooding.

Florence will slowly move west before curving rather sharply north Mon. then northeast & accelerating early in the week as Florence gets caught up in the westerlies. Now that the tropical cyclone is inland, Florence has lost the majority of its energy source - the warm ocean water - & will rather quickly fill & weaken but still capable of dumping very heavy rain.

It looks like direct impacts on the U.S. will continue through Tue., the 18th or so in one form or another. Flooding may very well follow the path of the post-tropical low pressure from Eastern Tennessee northeastward through parts of Virginia, Pennsylvania, Maryland, New York & Massachusetts later in the weekend into the middle of the week!  River flooding will lag the flash flooding reaching record levels in some areas.

Bottom line: Don't panic but always be prepared.....

The map below is a mirror of the above spaghetti plots but shows an ensemble of all the model runs. DEFINITION OF ENSEMBLE MODELING: A set of forecasts that present the range of future weather possibilities. Multiple simulations are run, each with a slight variation of its initial conditions and with slightly perturbed weather models. These variations represent the inevitable uncertainty in the initial conditions and approximations in the models. They produce a range of possible weather conditions.

40 foot waves have been measure offshore of N. Carolina!:

Heavy rain by late week middle east coast.  Rainfall over parts of N. Carolina & Virginia will exceed 1-3 feet! 1-3 day rainfall:

4-6 day rainfall:



Tropical cyclone record rainfall (for a single storm) may be broken in some states:

Wide view of the busy Atlantic Basin.  Joyce developed over the N. Atlantic Wed.... in addition to Isaac - which has degenerated into a tropical wave over the Caribbean... & Helene.  Another wave is moving off Africa & will move westward.  Forecast models are also showing possible long range development near & south of Bermuda & northeast of the Bahamas.... as well as over the E. Atlantic later next week.... & a wave with very heavy rain has moved into Texas running out of warm water before it could develop further.

Isaac is an open wave (trough) over the Caribbean.  It doesn't seem likely that Isaac will be able to recover from strong shear.

Helene & Joyce are weakening & will stay far to the east over the open Atlantic.

E. Atlantic:




Mid & upper level wind shear (enemy of tropical cyclones) analysis (CIMMS). The red lines indicate strong shear.  Note weaker shear in the path of Florence over the W. Atlantic while there's much stronger shear over the Caribbean......

The Atlantic Basin....


Gulf of Mexico:

Water vapor imagery (dark blue indicates dry air) - notice the dry air right up against Florence:

Deep oceanic heat content is seasonably high over the Caribbean, Gulf of Mexico & SW Atlantic as one would expect now that we're near the peak of the hurricane season....

Sea surface temp. anomalies show a general recent warming over a good portion of the Atlantic Basin including rather dramatic warming east of the Caribbean & near the NE coast of S. America ....

SE U.S. surface map:

Surface analysis centered on the tropical Atlantic:

Surface analysis of the Gulf: