• STRMDISC: TS Gamma 9

    From Dumas Walker@21:1/175 to All on Sun Oct 4 20:27:00 2020
    903
    WTNT45 KNHC 041443
    TCDAT5

    Tropical Storm Gamma Discussion Number 9
    NWS National Hurricane Center Miami FL AL252020
    1000 AM CDT Sun Oct 04 2020

    An Air Force Reserve reconnaissance aircraft has found the center
    of Gamma over the far southern Gulf of Mexico, just north of the
    Yucatan Peninsula. Early morning visible satellite imagery has
    revealed decent banding structure over the northern and western
    portions of the circulation. The aircraft has measured a peak 850
    mb flight-level wind of 66 kt and SFMR winds of 47 kt. A blend of
    these data support an initial intensity of 50 kt, which is also in
    line with the latest Dvorak classifications of T3.0 and T3.5 from
    SAB and TAFB, respectively.

    Gamma appears to be slowing down as anticipated, with an initial
    motion estimate of 360/3 kt. Gamma is expected to meander over the
    southern Gulf of Mexico, just north of the northern coast of the
    Yucatan peninsula during the next 12-24 hours. By late Monday, the
    western portion of a subtropical ridge is expected to build
    westward over the northern Gulf of Mexico. This should cause Gamma
    to turn westward to west-southwestward through the remainder of the
    forecast period. The dynamical model guidance is in general
    agreement on this scenario, but there are some differences in how
    close Gamma tracks to the northwestern portion of the Yucatan
    peninsula. The NHC track splits these differences and is a blend
    TCVA multi-model consensus and the HFIP corrected consensus. The
    new track forecast is very close to the previous official forecast.

    Although Gamma has re-strengthened this morning, increasing
    southerly wind shear is expected over the cyclone by tonight.
    This unfavorable upper-level environment is likely to cause
    some gradual weakening by late tonight and Monday. Since the
    vertical shear expected to remain moderate to strong through the
    latter portion of the forecast period, little overall change in
    strength is shown after 48 hours.


    KEY MESSAGES:

    1. Gamma is expected to produce heavy rainfall for several days over
    portions of southeastern Mexico, the Yucatan Peninsula, Central
    America, and far western Cuba. This rainfall could result in
    life-threatening flash flooding and mudslides, particularly in the
    mountainous regions of southeastern Mexico and Central America.

    2. Even though Gamma is offshore, tropical storm conditions will
    continue across portions of the northern coast of the Yucatan
    Peninsula today.


    FORECAST POSITIONS AND MAX WINDS

    INIT 04/1500Z 22.2N 88.2W 50 KT 60 MPH
    12H 05/0000Z 22.6N 88.2W 50 KT 60 MPH
    24H 05/1200Z 22.6N 88.5W 45 KT 50 MPH
    36H 06/0000Z 22.3N 89.3W 40 KT 45 MPH
    48H 06/1200Z 22.0N 90.2W 40 KT 45 MPH
    60H 07/0000Z 21.5N 91.0W 40 KT 45 MPH
    72H 07/1200Z 21.0N 91.6W 40 KT 45 MPH
    96H 08/1200Z 20.4N 92.5W 40 KT 45 MPH
    120H 09/1200Z 20.4N 93.0W 40 KT 45 MPH

    $$
    Forecaster Brown
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