• Talking the Tropics With Mike: Bahamas' disturbance slowly organizing with Florida impacts possible

    By: Michael Buresh

    Updated:

    Sept. 12, 2019 - The "Buresh Bottom Line": Always be prepared!.....First Alert Hurricane Survival Guide... City of Jacksonville Preparedness Guide... Georgia Hurricane Guide.  

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    Potential local - Jacksonville/NE Fl./SE Ga. - impacts from tropical disturbance '95-L' - magnitude to be determined by exact location & intensity of the system relative to Jacksonville!:

    * increasing showers & scattered t'storms over the weekend

    * rough seas & surf with a high rip current risk.  Best advice is to stay out of the ocean Sat./Sun.

    * minor flooding along the coast as well as the St. Johns River & its tributaries, especially at times of high tide with some astronomical boost from the full moon phase.

    * breezy winds out of the east

    The tropical wave/disturbance - over & near the SE Bahamas  - continues to move slowly west/northwest.  Hurricane hunter aircraft is scheduled to investigate this disturbance Thu. afternoon if the system appears to be organizing. There have been occasional ship reports of winds greater than 40 mph.  Though not in a favorable area for much development at the moment - a good deal of shear out of the west & southwest at 30-40 mph - the wave will find a more favorable environment near Fl. by the weekend.  For the hard hit Northern Bahamas, this wave will bring some heavy rain & - at times - gusty winds but at this time a well organized tropical system is not expected to develop while in the vicinity of the Bahamas. But the heavy rain & gusty winds will interfere with search & rescue/recovery operations.   

    Exactly what this wave will become is a bit problematic.  Overall conditions look favorable for organization over the weekend.  Proximity to land + a generally disorganized wave initially may hamper development. The poorly organized "center" may very well "jump around" the next few days trying to couch itself under the strongest convection. 

    But we'll need to watch for a "sweet spot" that could result in fairly fast organization &, therefore, strengthening later in the weekend into early next week.  Anyone along the Gulf Coast from New Orleans to Mobile as well as all of Florida & even north to the Carolina's should stay up to date on the latest forecasts.  The European forecast model has been shifting north & east.  So much so as to keep the system east of Florida & Jacksonville in the latest operational (every 6 hours) output. The GFS is farther west & generally weaker taking a weak tropical cyclone across Fl. & into the Gulf of Mexico... the UKMET is close to the European solution (but has struggled some this season so far).  There is also some low pressure trying to develop over the Western Gulf of Mexico that may a play a role in the final outcome of '95-L' as it appears that some models may be having difficulty differentiating between the two. The positioning & strength of the Bermuda high over the Atlantic plus an incoming upper level trough over the Northeast U.S. will again (like Dorian) play an important role in the eventual track.

    The more east outcome would bring the east coast of Florida north to the Carolina's into the impact area with the Gulf Stream possibly adding some "energy" for any tropical development (though some upwelling remains from Dorian).... while a more west outcome would mean more rain for Fl. followed by potential impacts on the Central &/or Eastern Gulf Coast.

    5-day rainfall forecasts from the European (now east with disturbance) & GFS (more south & west with disturbance) respectively:

    Thanks to Dorian, sea surface temps. have dropped noticeably from the Northern Bahamas extending northward for hundreds of miles.  Upwelling like this can last for at least a week depending on weather & wind conditions.  Otherwise.... sea surface temps. remain generally above avg. over the SW Atlantic & Gulf of Mexico.

    There are a couple of active tropical waves over the Central & East Atlantic with long term potential with the big question mark.  It looks like the wave will remain rather weak which would allow the trade winds to steer a more shallow disturbance more west (vs. north).  Plenty of time to watch/monitor/track & "cipher".  Most of the more reliable global forecast models - European/GFS/UKMET - are bouncing around on any development not to mention the location.

     

     

    An examination of dust over the Atlantic shows generally less dust over the basin vs. past months which is fairly typical for September & the peak of the hurricane season.

    2019 names..... "Humberto" is next on the Atlantic list (names are picked at random... repeat every 6 years... historic storms are retired (Florence & Michael last year) & Dorian is almost certain to be next:

     

    East Atlantic:

    Mid & upper level wind shear (enemy of tropical cyclones) analysis (CIMMS). The red lines indicate strong shear of which there is plenty across the Atlantic at the moment:

    The Atlantic Basin:

    Water vapor imagery (dark blue indicates dry air):

    Deep oceanic heat content:

    Sea surface temp. anomalies show a warm Gulf of Mexico, Central & Northwest Atlantic while the "Main Development Region" (MDR) remain cooler than avg.  Note the upwelling (cooler water) left behind Dorian over the Bahamas & east of Florida:

    While the MDR is cooler than avg., it's important to realize the water is still warm enough to support tropical systems....

    SE U.S. surface map:

    Surface analysis centered on the tropical Atlantic:

    Surface analysis of the Gulf:

    Caribbean:

     

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