• STRMDISC: Hurricane Erin Discussion Number 39

    From COD Weather Processor@1:2320/105 to wx-atlan@lists.illinois.edu on Thursday, August 21, 2025 02:47:08
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    WTNT45 KNHC 210246
    TCDAT5

    Hurricane Erin Discussion Number 39
    NWS National Hurricane Center Miami FL AL052025
    1100 PM EDT Wed Aug 20 2025

    Satellite imagery and reports from an Air Force Reserve Hurricane
    Hunter aircraft indicate little change in Erin during the past
    several hours. The aircraft reported a central pressure near 942
    mb, and the wind data showed two concentric wind maxima - a weaker
    one about 15 n mi from the center and a stronger one 60-70 n mi
    from the center. The maximum 700-mb flight-level winds in the outer
    wind band are near 105 kt. Based on the lack of change since
    earlier, the initial intensity remains 95 kt, which is near the
    average of the various subjective and objective satellite intensity
    estimates.

    The initial motion is now 010/14 kt. The steering scenario and
    track forecast reasoning are again unchanged from the previous
    advisory. Erin should move around the western and northwestern
    periphery of the subtropical ridge during the next 12-24 h, passing
    between Bermuda and the U.S. east coast. After that, the system
    should accelerate northeastward and east-northeastward while
    embedded within the mid-latitude westerlies over the north
    Atlantic. The track guidance has changed little, and the new track
    forecast is an update of the previous forecast.

    A little strengthening could occur during the next 12 h or so,
    although the concentric wind maxima structure argues against
    significant strengthening. After 12 h, Erin should encounter
    increasing westerly shear and move over colder sea surface
    temperatures, which should result in steady weakening. The system
    is also expected to merge with a frontal system to become an
    extratropical low, and while this is currently forecast to occur
    by 72 h it could happen earlier. Erin should continue to weaken
    after extratropical transition as it moves east-northeastward
    across the north Atlantic.

    Erin is an unusually large hurricane. For hurricanes north of 30N
    latitude, its tropical-storm-force wind radii are in the 75th
    percentile of the Atlantic basin record.

    KEY MESSAGES:

    1. Erin is expected to produce life-threatening surf and rip
    currents along the beaches of the Bahamas, much of the east coast of
    the U.S., Bermuda, and Atlantic Canada during the next several days.
    Beachgoers in those areas should follow advice from lifeguards,
    local authorities, and beach warning flags.

    2. Storm surge flooding and tropical storm conditions are expected
    in the North Carolina Outer Banks through Thursday. The storm surge
    will be accompanied by large waves, leading to significant beach
    erosion and overwash, making some roads impassible.

    3. Tropical storm conditions are expected on Thursday along the
    Virginia coast. Wind gusts to tropical storm force are likely along
    portions of the remainder of the U.S. Mid-Atlantic and southern New
    England coasts Thursday through early Friday.

    4. Tropical storm conditions are possible on Bermuda on Thursday and
    Friday. Gusts to gale force are possible along the coast of Nova
    Scotia on Friday and Newfoundland on Saturday.


    FORECAST POSITIONS AND MAX WINDS

    INIT 21/0300Z 32.8N 73.1W 95 KT 110 MPH
    12H 21/1200Z 34.8N 71.7W 95 KT 110 MPH
    24H 22/0000Z 36.8N 69.0W 90 KT 105 MPH
    36H 22/1200Z 38.7N 65.2W 85 KT 100 MPH
    48H 23/0000Z 40.4N 60.5W 75 KT 85 MPH
    60H 23/1200Z 42.2N 54.3W 65 KT 75 MPH
    72H 24/0000Z 44.5N 46.8W 50 KT 60 MPH...POST-TROP/EXTRATROP
    96H 25/0000Z 50.0N 31.1W 45 KT 50 MPH...POST-TROP/EXTRATROP
    120H 26/0000Z 54.3N 21.8W 40 KT 45 MPH...POST-TROP/EXTRATROP

    $$
    Forecaster Beven


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