• Talking the Tropics With Mike: Bahamian disturbance slowly moving W/NW

    By: Michael Buresh

    Updated:

    Sept. 11, 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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    RECAP "Hurricane Dorian: A True Tropical Beast"

    The Atlantic Basin remains active.....

    Beginning close to home - over & near the SE Bahamas  - a tropical wave is moving slowly west/northwest.  Hurricane hunter aircraft is scheduled to investigate this disturbance Thu. afternoon if the system appears to be organizing. Thought not in a favorable area for much development for 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. & over the Gulf of Mexico by the weekend into early next week.  For the hard hit Northern Bahamas, this wave will bring some heavy rain & - at times - gusty winds but a well organized tropical system is not expected to develop while in the vicinity of the Bahamas. But the wave will interfere with search & rescue/recovery operations. 

    Heavy rain & storms will increase for the Florida Peninsula Friday through especially the weekend.  

    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" 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 should stay up to date on the latest forecasts.  The European forecast model has been shifting north... the GFS is farther west & generally weaker... the UKMET is farther east near the east coast of Florida & a little stronger (but has struggled some this season so far).

    At the very least I'm anticipating heavy rain at times Friday through Sunday/Monday for most of Florida & the North Central / Northeast Gulf of Mexico.

    5-day rainfall forecasts from the European & GFS 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.

    It's the peak of the Atlantic hurricane season. On or near Sept. 10th, there is on avg. at least 1 named storm over the Atlantic 75% of the time... & two or more named storms 50% of the time.  Tropical storm "Gabrielle" was over the N. Atlantic on the morning of the 10th but became extratropical later in the day as the NHC issued their last advisory.

    Phil Klotzbach - September landfalling hurricanes:

     

    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.

    '94-L' spaghetti plots:

     

     

    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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