• Pacific-EN: TS Blanca D5

    From Weather Alert@1:2320/105 to All on Mon May 31 18:14:00 2021
    WTPZ42 KNHC 312042
    TCDEP2

    Tropical Storm Blanca Discussion Number 5
    NWS National Hurricane Center Miami FL EP022021
    300 PM MDT Mon May 31 2021

    Thunderstorms activity has increased markedly since the previous
    advisory and convection now wraps almost 75 percent around the
    well-defined low-level center. A bullseye ASCAT-B and a partial
    ASCAT-A pass at 1717Z and 1602Z, respectively, depicted a few
    35-kt surface vectors just northwest of the tight low-level center
    along with a small radius of maximum winds (RMW) of about 15 nmi.
    Based on the continued increase in the convective organization since
    the ASCAT passes, the advisory intensity has been raised to 40 kt,
    which is a little below the consensus T3.0/45 kt satellite
    intensity classifications from TAFB and SAB, and objective intensity
    estimates of 46 kt and 47 kt from UW-CIMSS ADT and SATCON,
    respectively.

    Blanca is forecast to maintain a general west-northwestward to
    northwestward motion along the south side of a deep-layer
    subtropical ridge for the next 3 days or so. Thereafter, a gradual
    turn to the west-northwest is expected on day 4, followed by a
    westward motion on day 5 as the cyclone moves over cooler water and
    weakens, thus becoming more vertically shallow and steered by the
    low-level easterly trade wind flow. The new official NHC forecast
    track is similar to the previous advisory track and lies near the
    center of the tightly packed guidance envelope, which is close to
    an average of the consensus track models TVCE and HCCA.

    Blanca is expected to remain in favorable environmental conditions
    of low vertical wind shear less than 10 kt, high oceanic heat
    content, and moist low- to mid-level air for the next 24 hours or
    so. As a result, steady strengthening is forecast during that
    time, with a brief period of rapid intensification a distinct
    possibility owing to the cyclone's small RMW. Thereafter, the
    combination of increasing westerly wind shear, along with
    decreasing SSTs and mid-level humidity, should cause gradual
    weakening. The new NHC intensity forecast is a blend of the HWRF,
    HCCA, and Decay-SHIPS (DSHP) models, which is slightly above the
    previous intensity forecast for the first 24 hours, and then is
    very similar to the previous advisory thereafter.


    FORECAST POSITIONS AND MAX WINDS

    INIT 31/2100Z 13.5N 108.9W 40 KT 45 MPH
    12H 01/0600Z 14.0N 109.9W 50 KT 60 MPH
    24H 01/1800Z 14.6N 111.0W 55 KT 65 MPH
    36H 02/0600Z 15.2N 112.1W 45 KT 50 MPH
    48H 02/1800Z 15.6N 113.0W 40 KT 45 MPH
    60H 03/0600Z 15.9N 113.7W 35 KT 40 MPH
    72H 03/1800Z 16.0N 114.4W 35 KT 40 MPH
    96H 04/1800Z 16.2N 116.2W 30 KT 35 MPH
    120H 05/1800Z 16.2N 118.1W 25 KT 30 MPH

    $$
    Forecaster Stewart
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