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  • STRMDISC: Tropical Storm Lorenzo Discussion Number 2

    From COD Weather Processor@1:2320/105 to [email protected] on Mon Oct 13 14:53:49 2025
    200
    WTNT42 KNHC 131453
    TCDAT2

    Tropical Storm Lorenzo Discussion Number 2
    NWS National Hurricane Center Miami FL AL122025
    1100 AM AST Mon Oct 13 2025

    Lorenzo has maintained a large area of convection with cold cloud
    tops, although the latest GOES-19 1-minute visible satellite images
    suggest that the low-level center is near the southwestern edge of
    this convection, which makes sense due to the strong southwesterly
    wind shear over the cyclone. Overall, Lorenzo's structure hasn't
    changed much over the past 6 hours. However, a timely recent ASCAT
    pass shows a large area of 40-45 kt winds mainly in the northeast
    quadrant, so the initial intensity is increased to 45 kt, which is
    slightly above the latest objective current satellite intensity
    estimates from UW-CIMSS.

    The initial motion estimate is northwestward, or 310 degrees at 14
    kt. Lorenzo is near the southwestern periphery of a mid-level high
    centered near the Cabo Verde Islands. Farther northwest, a mid- to
    upper-level trough is acting to erode the subtropical ridge. This
    trough is expected to fracture and shift to the southwest of the
    system, and Lorenzo should turn northward on Tuesday between this
    feature and the eroded mid-level ridge centered over the Cabo Verde
    Islands. Lorenzo is forecast to recurve northeastward on Wednesday
    as the cyclone comes under the influence of broad-scale mid-latitude
    westerly flow. If Lorenzo is still alive by Friday, it could
    approach a weakness in steering flow, with mid- to upper-level
    ridging possibly centered to the north or northeast of the cyclone,
    so the track forecast shows a slowdown with a turn to the east in
    4-5 days. The track guidance is in good agreement through the 72
    hour point, but spread increases significantly after that time. The
    new NHC track forecast is slightly west of the previous NHC
    prediction through hour 60, and lies close to the HFIP Corrected
    Consensus (HCCA) during that time period. At Day 5, the new NHC
    forecast is south of the previous prediction.

    Lorenzo continues to experience about 25 kt of southwesterly wind
    shear, although the shear is forecast to decrease significantly
    later today, and relatively light shear is anticipated from tonight
    through Thursday. Ordinarily, this would lead to strengthening
    given the sufficently warm 27-28 C ocean temperatures, but at the
    same time, environmental mid-level relatively humidity is also
    expected to decrease substantially as the storm interacts with the
    upper-level trough ahead of it. This trough could also still
    produce some residual mid-level shear undercutting the outflow
    layer. Most of the intensity guidance is not that enthusiastic
    about Lorenzo's prospects, but there are a couple of ECMWF ensemble
    members and a handful of Google DeepMind ensemble members that make
    Lorenzo a hurricane. The NHC intensity forecast is unchanged from
    the previous advisory other than the slightly stronger initial
    intensity, and is near the high end of the intensity guidance suite,
    showing little change in strength in the short-term, and then
    gradual intensification afterwards. The NHC intensity forecast is
    still generally higher than the HCCA, HAFS, and the intensity
    consensus. There is some possibility that the aforementioned dry
    air could cause Lorenzo to dissipate before the end of the 5-day
    period, as suggested by some of the global and hurricane regional
    models, but the NHC forecast maintains it as a tropical storm.


    FORECAST POSITIONS AND MAX WINDS

    INIT 13/1500Z 14.8N 41.2W 45 KT 50 MPH
    12H 14/0000Z 15.6N 42.7W 45 KT 50 MPH
    24H 14/1200Z 17.2N 44.1W 45 KT 50 MPH
    36H 15/0000Z 19.2N 44.9W 45 KT 50 MPH
    48H 15/1200Z 21.4N 44.9W 50 KT 60 MPH
    60H 16/0000Z 23.9N 43.5W 55 KT 65 MPH
    72H 16/1200Z 26.7N 41.2W 60 KT 70 MPH
    96H 17/1200Z 31.4N 34.4W 55 KT 65 MPH
    120H 18/1200Z 31.8N 29.8W 45 KT 50 MPH

    $$
    Forecaster Hagen


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