• STRMDISC: Tropical Storm Melissa Discussion Number 12

    From COD Weather Processor@1:2320/105 to wx-atlan@lists.illinois.edu on Friday, October 24, 2025 08:42:23
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    WTNT43 KNHC 240842
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    Tropical Storm Melissa Discussion Number 12
    NWS National Hurricane Center Miami FL AL132025
    500 AM EDT Fri Oct 24 2025

    For all intents and purposes, Melissa is nearly stationary over the north-central Caribbean Sea. The estimated center has been
    adjusted a bit based on scatterometer data from last evening, but
    wind direction data from buoy 42058 also suggest that the
    circulation could still be a bit elongated. There are several deep
    convective bursts embedded within the overall cloud canopy,
    although banding features are not particularly well defined at the
    moment. An Air Force Reserve mission should provide a more accurate
    estimate of Melissa's center location and intensity in a couple of
    hours, and for now the estimated intensity is maintained at 40 kt.

    With Melissa located within a break in the mid-level ridge, the
    steering currents remain weak. Track models suggest that some
    meandering or a slow northeast to north drift is likely to occur
    over the next 24 hours. By Saturday, there will likely be just
    enough mid-level ridging building north of the storm to cause
    Melissa to begin moving very slowly westward, with that motion
    continuing through Tuesday. What's most noteworthy is that several
    reliable models, including the ECMWF, HCCA, and Google DeepMind
    ensemble mean have shifted southward during this period. The new
    NHC forecast reflects this slight shift, but it's important to note
    that several other models continue to show Melissa's center getting
    perilously close to or over Jamaica in 2-3 days. A slow
    recurvature is forecast on days 4 and 5, with Melissa potentially
    moving near western Jamaica and approaching southeastern Cuba by
    early Wednesday. Interestingly, the 00z ECMWF keeps Melissa south
    or southwest of Jamaica through day 5, but it appears to be an
    outlier compared to the other guidance.

    Strong westerly shear continues to affect Melissa, but there are
    some indications that the shear could gradually decrease over the
    next 24-36 hours. At the same time, high ocean heat content values
    and stronger upper-level divergence should help to induce
    strengthening. There is fairly strong agreement among the
    intensity models that a period of rapid intensification could begin
    in about 24 hours, and the NHC forecast shows Melissa becoming a
    hurricane in 36 hours. Although this is an aggressive forecast
    given Melissa's current structure, several models are even stronger
    than the NHC forecast at that forecast time. There is less model
    agreement on Melissa's intensity after 48 hours. In order to
    maintain continuity with previous forecasts, the NHC prediction is
    near the top end of the guidance envelope and close to the Google
    DeepMind ensemble mean. Other models show flatlining or decreasing
    intensity after 48 hours, but that is likely due to scenarios that
    account for more land interaction.


    Key Messages:

    1. Jamaica: Due to Melissa's slow motion, the risk of a prolonged
    multi-day period of potentially damaging winds, heavy rainfall
    resulting in life-threatening flash flooding and numerous
    landslides, and storm surge continues to increase for Jamaica.
    Preparations to protect life and property should be rushed to
    completion, since strong winds and flooding rains could begin in
    Jamaica later today or on Saturday.

    2. Haiti: Heavy rainfall will result in catastrophic flash
    flooding and landslides across southwestern Haiti by this weekend
    into early next week. Extensive damage to roads and buildings is
    expected, potentially isolating communities for an extended period
    of time. This is a life-threatening situation and immediate
    preparations to protect life and property should be taken. Strong
    winds could also potentially last for a day or more over the Tiburon
    peninsula of Haiti.

    3. Remainder of Hispaniola and Eastern Cuba: Heavy rainfall could
    also produce significant, life-threatening flash flooding and
    numerous landslides in southern Dominican Republic. Interests in
    Cuba should monitor the progress of Melissa since the risk of heavy
    rainfall, damaging winds, and storm surge appears to be increasing.


    FORECAST POSITIONS AND MAX WINDS

    INIT 24/0900Z 16.0N 75.5W 40 KT 45 MPH
    12H 24/1800Z 16.1N 75.3W 45 KT 50 MPH
    24H 25/0600Z 16.6N 75.4W 55 KT 65 MPH
    36H 25/1800Z 16.9N 75.9W 65 KT 75 MPH
    48H 26/0600Z 16.9N 76.5W 85 KT 100 MPH
    60H 26/1800Z 16.9N 77.2W 100 KT 115 MPH
    72H 27/0600Z 16.9N 78.0W 115 KT 130 MPH
    96H 28/0600Z 17.6N 78.8W 125 KT 145 MPH
    120H 29/0600Z 19.8N 77.9W 120 KT 140 MPH

    $$
    Forecaster Berg



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