• STRMDISC: TS Beta 7

    From Weather Alert@21:1/175 to All on Saturday, September 19, 2020 09:03:00
    322
    WTNT42 KNHC 190853
    TCDAT2

    Tropical Storm Beta Discussion Number 7
    NWS National Hurricane Center Miami FL AL222020
    400 AM CDT Sat Sep 19 2020

    Beta has generally changed little overnight. The storm is still
    quite asymmetric due to southwesterly wind shear with the low-level
    center located near the southwestern edge of the main area of deep
    convection. An ASCAT pass from a few hours ago showed peak winds in
    the 40-45 kt range, with most of the tropical-storm-force winds on
    the north side of the circulation. In addition, the latest Dvorak classifications are 3.0/45 kt from TAFB and SAB. The initial
    intensity of 50 kt, based on the earlier aircraft data, is a little
    above the satellite estimates. The Air Force Hurricane Hunters are
    scheduled to investigate Beta again later this morning, and the data
    they collect will provide a better estimate of the intensity and
    structure of the storm.

    Beta is moving northward, with the latest initial motion estimated
    to be 360/7 kt. The shortwave trough that has been causing the
    north to northeastward motion during the past day or so is moving
    away and a weak mid-level ridge is expected to build to the north of
    the storm soon. This change in the steering pattern should cause
    Beta to turn westward and slow down later today and then move
    generally westward to northwestward through the remainder of the
    weekend and into early next week. This motion should take Beta
    toward the Texas coast by Monday. Around the time Beta is forecast
    to be near the Texas coastline, the ridge is expected to retreat as
    another shortwave trough approaches, which should cause the storm to
    slow down even more and gradually turn to the northeast near the
    Texas coast by the middle of next week. The models are in fair
    agreement, and the NHC track forecast lies close to the various
    consensus aids.

    As mentioned above, the tropical storm is still feeling some
    effects of southwesterly wind shear, but the upper-level pattern is
    expected to become more favorable for strengthening later today.
    Although the shear is expected to lessen, water vapor images show a
    swath of dry air approaching the storm from the west. Based on
    these mixed environmental conditions, slow strengthening is
    forecast during the next couple of days and Beta is forecast to
    reach hurricane intensity in about 36 hours. Beyond a few days,
    the models suggest that there could be another increase in
    southwesterly shear, which in combination with land interaction
    should cause some weakening. Of course, the rate of weakening will
    depend on whether Beta is inland or offshore. The NHC intensity
    forecast is largely an update of the previous one and lies at the
    high end of the model guidance.

    Key Messages:

    1. There is an increasing risk of heavy rainfall and flooding along
    the northwest Gulf Coast Sunday through at least the middle of next
    week as Beta is forecast to move slowly toward and along or offshore
    of the coast through that time. For additional information, see
    products from your local National Weather Service office.

    2. Life-threatening storm surge and hurricane-force winds are
    possible along portions of the Texas coast early next week, with
    tropical storm conditions possible by late this weekend. Storm Surge
    and Hurricane watches are in effect, and residents in these areas
    should ensure they have their hurricane plan in place and follow
    advice given by local officials.


    FORECAST POSITIONS AND MAX WINDS

    INIT 19/0900Z 26.0N 92.5W 50 KT 60 MPH
    12H 19/1800Z 26.6N 92.6W 55 KT 65 MPH
    24H 20/0600Z 26.9N 93.4W 60 KT 70 MPH
    36H 20/1800Z 27.1N 94.3W 65 KT 75 MPH
    48H 21/0600Z 27.4N 95.2W 70 KT 80 MPH
    60H 21/1800Z 27.7N 95.9W 70 KT 80 MPH
    72H 22/0600Z 28.1N 96.3W 65 KT 75 MPH
    96H 23/0600Z 28.7N 95.4W 60 KT 70 MPH
    120H 24/0600Z 29.7N 93.3W 50 KT 60 MPH

    $$
    Forecaster Cangialosi
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