• Talking the Tropics With Mike: Hybrid-type Chantal over N. Atlantic; trop disturbance near Bahamas

    By: Michael Buresh


    Aug. 21, 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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    The peak of the hurricane season is essentially here.  Two-thirds of all Atlantic hurricanes occur between Aug. 20th & Oct. 10th.

    And right on cue - "Chantal" has developed over the N. Atlantic from a low pressure system that originally formed near Jacksonville over the weekend. The compact more hybrid-like storm (vs. fully warm core) will move east then slow & turn southward west of the Azores Islands & well east of Bermuda.  No impact on the U.S.

    The velocity potential anomaly map below shows rising vertical velocities (green lines) overspreading the Pacific Basin.  This should help with some tropical development in the short term over the Eastern Pacific & eventually - by late Aug. - over parts of the Atlantic Basin.  And could help get something going this week over the Gulf of Mexico.

    Meanwhile.... a tropical wave that came off the coast of Africa last week is just east of the Central Bahamas with t'storms that have flared the last day or so.  Surface low pressure may evolve from this wave & try to organize east of Fl. over the weekend while moving N/NW then turning more north.  Proximity to the warm Gulf Stream + marginal shear + an approaching upper level trough may all help this system to develop over the next 3-5 days.  Any impacts to Florida/Jacksonville/SE Ga. look to be minor - mostly - perhaps - a bump in seas & surf.  The backside (west) of tropical waves are typically drier vs. near the center & to the east of the wave axis.

    Few models show development yet so the model plot is rather meager for the moment:

    Below is the GFS model forecast for late Sat. showing just enough of an upper level trough to the north to help pull the Bahama disturbance northward.

    At the surface - again for late Sat. - strong high pressure over SE Canada moving into New England argues for lowering pressures to the south which would favor low pressure & possible tropical development approximately in the vicinity of the Bahamas.

    Another area to watch into the weekend will still be the Western Gulf of Mexico.  A pretty decent tropical wave (tied to "disturbed" weather over the NW Caribbean) & upper level disturbance will work NW then northward into & over the Western Gulf by mid to late week.  While models show only weak surface development - if any at all - this will be an area to watch for "sneaky" development in an area - historically speaking, the Western Gulf  - that is highly favored in mid to late Aug.

    Rainfall forecast shows the tropical "trouble spots" receiving heavy rain as well as along front from the Midwest to the middle Atlantic Coast.



    An examination of dust over the Central & Eastern Atlantic shows a continuation of a good deal of dust over the Central & Eastern Atlantic as well as parts of the Caribbean.  While such dry air can inhibit tropical development initially, once any waves are farther west or if the wave can stay a little south & out of the dust "cloud" - & IF all other conditions are equal - organization/strengthening can occur.  The 2005 hurricane season stands out (along with several other seasons) as a "dusty" Eastern Atlantic but disturbances simply waited to get out of the dust - further to the west - to develop & then "make history".

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


    Atlantic Basin today - note strong tropical wave coming off the coast of Africa....

    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. along with parts of the Central Caribbean.....

    SE U.S. surface map:

    Surface analysis centered on the tropical Atlantic:

    Surface analysis of the Gulf:



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