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  • STRMDISC: Hurricane Imelda Discussion Number 22

    From COD Weather Processor@1:2320/105 to [email protected] on Thu Oct 2 02:51:55 2025
    190
    WTNT44 KNHC 020251
    TCDAT4

    Hurricane Imelda Discussion Number 22
    NWS National Hurricane Center Miami FL AL092025
    1100 PM AST Wed Oct 01 2025

    Data from the Air Force Reserve reconnaissance aircraft this evening
    found that Imelda is likely in the early to mid stages of
    extratropical transition. In addition to the aircraft crossing a
    baroclinic zone just to the north of the hurricane's core, the winds
    have become very asymmetric, with hurricane-force winds around the
    western and southeastern sides of the circulation, but much lighter
    winds to the northeast. The aircraft also found rising pressure
    between fixes, and the earlier eyewall reported from the prior
    mission has been reduced to a small fragment on the northwestern
    side. Despite the degraded presentation, the 700 mb flight-level
    winds were a little higher than the prior mission, peaking at 98 kt
    in the southeastern quadrant. While this would normally translate to
    a somewhat higher 90 kt maximum sustained wind, these flight-level
    winds occurred where Imelda has little in the way of precipitation
    according to the Bermuda radar. Thus, the initial intensity will
    remain 85 kt for this advisory, using a slightly lower surface wind
    reduction.

    Aircraft fixes and Bermuda radar imagery indicate that Imelda
    continues to accelerate quickly to the east-northeast, with its
    estimated motion now at 075/25 kt. This motion will likely take the
    hurricane's inner eyewall fragment right over the island of Bermuda
    over the next couple of hours. The strongest winds associated with
    Imelda are likely to be felt just after the center passes by,
    thanks to the increasingly asymmetric wind-field of the hurricane.
    In fact, the global and hurricane-regional models show a distinct
    sting-jet like signature on the backside that both 18 UTC HAFS-A/B
    and the 12 UTC ECMWF show moving directly over Bermuda between now
    and the 06 UTC time frame. After passing Bermuda, the global and regional-hurricane models show the hurricane completing
    extratropical transition as the frontal boundary merges in with the
    cyclone's core. The NHC intensity forecast is a little lower than
    the prior advisory, but remains in good agreement with the consensus
    aids HCCA/IVCN.

    After Imelda clears Bermuda and becomes fully extratropical, the
    models are in better agreement about the cyclone turning
    northeastward by late Thursday or Friday when it fully phases with a
    digging shortwave trough located upstream of the system. While
    significant model spread persists, the 18 UTC GFS has come into
    better agreement with the other global model guidance showing this
    phasing solution rather than being left behind the trough. The
    latest NHC track forecast this evening is roughly a blend of the
    HFIP corrected consensus aid (HCCA) and the faster Google DeepMind
    ensemble mean (GDMI).


    KEY MESSAGES:

    1. Imelda's core is currently near Bermuda and is expected to bring
    damaging hurricane-force winds and large and damaging waves to
    Bermuda as it moves over the island now into early Thursday.
    Significant hurricane-force gusts are likely across Bermuda even
    after the center passes.

    2. Heavy rainfall could cause flash flooding across Bermuda tonight
    into Thursday.

    3. Swells and high surf from Imelda are expected to produce
    dangerous marine conditions and rip currents along much of the East
    Coast of the United States and the western Atlantic during the next
    several days.


    FORECAST POSITIONS AND MAX WINDS

    INIT 02/0300Z 32.1N 65.0W 85 KT 100 MPH
    12H 02/1200Z 32.8N 60.7W 80 KT 90 MPH...POST-TROP/EXTRATROP
    24H 03/0000Z 34.0N 55.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
    36H 03/1200Z 36.2N 51.3W 60 KT 70 MPH...POST-TROP/EXTRATROP
    48H 04/0000Z 38.6N 49.4W 55 KT 65 MPH...POST-TROP/EXTRATROP
    60H 04/1200Z 41.4N 47.3W 50 KT 60 MPH...POST-TROP/EXTRATROP
    72H 05/0000Z 44.5N 43.7W 45 KT 50 MPH...POST-TROP/EXTRATROP
    96H 06/0000Z 49.5N 34.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
    120H 07/0000Z 51.2N 28.0W 40 KT 45 MPH...POST-TROP/EXTRATROP

    $$
    Forecaster Papin


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