• MESO: Mesoscale Discussion 1732

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun Sep 12 22:53:19 2021
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    ACUS11 KWNS 122253
    SPC MCD 122252=20

    Mesoscale Discussion 1732
    NWS Storm Prediction Center Norman OK
    0552 PM CDT Sun Sep 12 2021

    Areas affected...Parts of southern lower Michigan

    Concerning...Severe Thunderstorm Watch 493...494...

    Valid 122252Z - 130045Z

    The severe weather threat for Severe Thunderstorm Watch 493, 494

    SUMMARY...An evolving cluster of thunderstorms may become better
    organized with increasing potential for damaging wind gusts, in
    addition to large hail, while progressing along a corridor near or
    just north of Grand Rapids and Detroit through 9-10 PM EDT.

    DISCUSSION...A pair of mid-level cyclonic vorticity centers have
    contributed to ongoing vigorous thunderstorms development while
    migrating eastward along a 50-70 kt westerly 500 mb jet. The
    convection appears to be generally rooted within moist air above/to
    the north of a quasi-stationary frontal zone, near the northern
    periphery of plume of warm and capping elevated mixed-layer air
    emanating from the Great Plains.

    One cluster developed fairly far removed from the lead cyclonic
    vorticity center, now progressing across Lake Huron, and the warm
    elevated mixed-layer appears to be suppressing it as it approaches
    the international border area north of Detroit. The upstream
    cluster appears just ahead of the trailing cyclonic vorticity
    center, migrating inland off of Lake Michigan, to the
    northwest/north of Grand Rapids.=20=20

    The stronger mid-level forcing for ascent with the trailing
    thunderstorm cluster seems likely to maintain it across lower
    Michigan, near/north of Grand Rapids, Lansing and Ann Arbor, into
    the Flint vicinity and areas near/north of the Greater Detroit area
    by 01-02Z. Thermodynamic profiles characterized by steep mid-level
    lapse rates and sizable CAPE will remain conducive to large hail, in
    the presence of strong cloud-bearing layer shear. Although
    low-level lapse rates are generally weak, profiles are still
    relatively warm and saturated, and latent cooling due to melting
    hail in downdrafts may gradually contribute to downward transfer of
    the strong momentum in mid-levels, perhaps eventually accompanied by
    increasing risk for potentially damaging wind gusts.

    ..Kerr.. 09/12/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!oIVugcCwaDfW_gWK3OUm9OHHNi67OL3i7qiof8uuPqYI4bw-xR1fynbU4cclltt2AenkIzsW$=
    for graphic product...


    LAT...LON 43568540 43428412 43128258 42448281 42558393 42758533
    43028594 43228539 43568540=20

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