Talking the Tropics With Mike: Hurricane Florence weakens but still a big threat to Carolina's

Sept. 13, 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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At Jacksonville, FL latitude late Wed. hundreds of miles to the east... still 250+ miles NE of Jacksonville at/near landfall late Thu./Thu. night/Fri.:

NEW "fork in the road"!: At or while approaching landfall Thu. night/Fri., the steering influences collapse & Florence will slow to a crawl.  At this point, Florence will drift &/or move erratically possibly including a move south &/or southwest.  As long as Florence makes landfall - or at least gets close enough to the coast to feel the effects (friction, dry air, shear) - the hurricane will weaken.  But this set-up & possibility deserves close attention, especially for S. Carolina & Eastern Georgia.


* Thu./Fri./Sat./Sun. - primary impacts look to be a breeze & very rough seas/surf & dangerous rip currents.  All boaters stay in port! Surfers will be tempted by decent & "clean" waves but beware of dangerous rip currents.  

* Virtually no impacts inland.

* Stay up to date on the latest & potentially changeable forecasts. 

* Despite the wide span of Florence's winds & rain, no rain bands will directly affect NE Fl./SE Ga.... & - in fact - skies will be relatively sunny late in the week into the weekend.  Strongest winds stay well offshore to the east & northeast of Jacksonville.  If Florence drop south & southwest, additional impacts would be possible but not until Sunday/Monday as it appears right now & not likely significant.

Everyone up & down the east coast of the U.S. - particularly the Carolina's - needs to stay vigilant regarding the latest forecasts...

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"Florence" which 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.  There will continue to be fluctuations - both up & down - in intensity.  Florence went through some serious structural alterations Wed. probably due to nearby dry air & some shear.  The eye was still open to the SE according to hurricane hunter aircraft as of late Wed. evening.  But the eye was also contracting which could signal a intensifying trend soon.

Despite recent weakening, Florence looks to be a big hit on the Carolina's:  Major to severe impacts can be expected on the S. & especially N. Carolina coasts. Don't make the mistake of getting too caught up in individual run output of any particular model.... OR in what unreliable sources might be posting.... OR tracking just the center!  Dangerous conditions will extend far from the eye of Florence.  And do NOT underestimate the power of Florence even though the storm has weakened.  Very heavy rain will cause widespread flooding, & the storm surge will likely be greater than what might usually be expected with a Cat. 2 storm.

As for the forecast models, there was a notable shift north over the weekend but seemingly a recent stabilization pointing to the Carolina's.  This could be thanks to the aircraft analysis that has been recently ingested into the computer models.  Virtually all reliable global models are - for now - pointing at or near the Carolina's - not far from or a little northeast of Myrtle Beach to Wilmington.  The UKMET, European & GFS models - have come into decent agreement on a hurricane near the Gulf Stream moving into N. Carolina &/or Northeast S. Carolina but have been too high on intensity.  For now... research aircraft is scheduled to continue gathering input for forecast models. That's in addition to special atmospheric soundings across the eastern half of the U.S. (4 balloon releases instead of the standard 2).  This data will be in the model initialization hopefully leading to an even more accurate long term track & intensity forecast.

Having said that - & as mentioned at the top - we have an increasing spread in what will happen Fri. into the weekend once Florence approaches the coast &/or moves inland.  The European & GFS models in particular are showing a propensity to move Florence south & southwest, at least some.  Exactly how much & at what strength is a big problem.  It does appear that such a move would be in a much weaker state given proximity to land.... or actually being over land but this part of the forecast is highly uncertain.  Either way this still looks like a major blow to the Carolinas & possibly SE Virginia but also parts of the upper Ga. coast perhaps ... depending on the southward drift or move.

Bottom line at this point: East Coast needs to stay alert & up to date & one should always be prepared for what mother nature might have in store.

The ultimate track now hinges on how strong high pressure will be across the N. Atlantic westward into the Northern U.S.  The orientation of the high will be important for the exact track, & I am concerned that models may not be producing a strong enough high.  If true then Florence's track may end up being at least somewhat farther south but still into the Carolina's - at least at first.  Once the steering currents collapse, Florence will flounder over or near the Carolina's pounding the beaches with wave action & dropping tremendous amounts of rain - most significant of these impacts will be north & northeast of the center.  Another high pressure cell building from the Midwest into the Ohio Valley may trap Florence over the Eastern &/or Southeast U.S.... or even push the storm southward some.

So overall.... the critical point - the fork in the road - when Florence was between Bermuda & the U.S. coast kept Florence on a straight forward west then northwest course. Now we have a 2nd fork in the road - the weekend developments/movement.  I continue to favor a scenario that takes Florence well northeast of Jacksonville in the short term hitting northeast of Myrtle Beach possibly as far north as near Wilmington, NC.. STAY UP TO DATE!  As Florence slows upon nearing the coast, flooding problems & beach erosion - especially north of the eye could be tremendous.... & will also make pinpointing landfall + the intensity extra problematic.

So review hurricane plans, kits & do some work on & around the house before any severe weather moves in (cleaning storm drains, gutters, etc.).  It looks like direct impacts on the U.S. will be from approximately Sept. 13-17th or so.

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

Eyewall replacement cycles:



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.

It's worth noting that there are a majority of model runs all the way to the U.S.  There has been a definite trend west & - recently - north the last several days followed by the potential move south over the weekend:

The Saharan dust (courtesy CIMMS) imagery shows pockets of dust (dry air) over the Central & Eastern Atlantic as well as the Eastern Caribbean..

Wave height model (GFS) forecast... European model a little more south & west which - if verifies - wave heights would be higher for NE Fl./SE Ga. but still much more significant for the coastal Carolina's north to Chesapeake Bay:

Heavy rain by late week middle east coast.  Rainfall over parts of N. Carolina & Virginia may exceed 1-2 feet!:

Wide view of the busy Atlantic Basin. This is only the 11th time since 1851 that there have been at least 3 active hurricanes over the Atlantic at the same time (Klotzbach) though Isaac weakened back to a tropical storm Mon. evening.  Joyce has also developed over the N. Atlantic making it 4 named storms at the same time - first such occurrence since 2008. Another wave is moving off Africa but doesn't appear as though it will develop.  Forecast models are also showing possible long range development near & south of Bermuda.

Helene & Isaac are over the far Eastern Atlantic.  Isaac will move farther west over the Atlantic as high pressure tries to assert itself across parts of the Central/Northern Atlantic & underneath Florence.  Shear looks to stay strong over the Caribbean in the long run which should cause Isaac - a small tropical cyclone - to weaken pretty quickly.  The GFS & European models are very similar in this regard.   Issac is approaching the islands of the Lesser Antilles where tropical storm WARNINGS are in effect.  IF Isaac can somehow survive its current hostile environment, somewhat more favorable conditions will be over the W. Caribbean & Gulf of Mexico.

Helene, on the other hand, looks like a full recurve over the Central/ E. Atlantic.  Helene might interact with Joyce over the N. Atlantic.  Both, however, stay far to the east over the open Atlantic.

I'm also keeping an eye on the NW Caribbean &/or Gulf of Mexico for possible tropical development.  There has been a persistent area of t'storms over the W. Caribbean - something to watch.  Movement will be west/northwest, so this will be a Western Gulf "thing" & not a problem for Florida.  Gulf disturbance spaghetti plots:

Isaac & Helene over the 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:


The Central Pacific: A pretty weak & sheared Olivia is moving over Hawaii - as a tropical storm - over the next couple days.  A tropical storm WARNING is in effect for many of the islands.  Rainfall & rough seas/surf will be the main stories but overall damage should be limited.


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