• MESO: Mesoscale Discussion 1543

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Aug 17 12:23:13 2021
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    ACUS11 KWNS 171223
    SPC MCD 171222=20

    Mesoscale Discussion 1543
    NWS Storm Prediction Center Norman OK
    0722 AM CDT Tue Aug 17 2021

    Areas affected...Parts of northeast and east central Georgia into
    western South Carolina

    Concerning...Tornado Watch 443...

    Valid 171222Z - 171415Z

    The severe weather threat for Tornado Watch 443 continues.

    SUMMARY...The development of isolated supercell structures with the
    potential to produce short-lived tornadoes remains possible to the
    northeast of the weakening remnants of Fred. This may gradually
    spread across the remainder of northeastern Georgia into Upstate
    South Carolina by 10 am-12 pm EDT. Trends are being monitored for
    the possibility of a new watch, but it is also possible that the
    threat may become marginal and/or isolated enough that a new watch
    may not be needed.

    DISCUSSION...More substantive central pressure rises have been
    occurring the past few hours as Fred migrates northward. A
    corresponding weakening of low-level wind fields has also been
    observed, and these trends are likely to continue as the depression
    progresses north-northeast of the Auburn, AL vicinity, toward the
    Greater Atlanta metro through 14-16Z.=20=20

    Mid-level subsidence warming nosing northeastward around the
    southern through eastern periphery of the circulation aloft is
    contributing to diminishing convective potential across the Warner
    Robins/Macon vicinity into the Greater Atlanta area, and this is
    forecast to continue spreading toward the Savannah River through mid
    to late morning. This also corresponds with a weak surface wind
    shift, and the onset more unidirectional shear in the near surface

    Ahead of the wind shift, strongest mid/upper forcing for ascent,
    low-level convergence and largest clockwise-curved low-level
    hodographs will generally be focused in an area overspreading
    northeastern Georgia into Upstate South Carolina through 14-16Z.=20
    Although wind fields are gradually weakening, southerly 850 mb flow
    on the order of 30+ kt may still contribute to sufficiently large
    low-level hodographs to maintain at least some risk for the
    development of supercell structures with the potential to produce=20
    tornadoes. This probably will be aided by at least some further
    increase of surface dew points through the lower to mid 70s F across
    parts of the Piedmont.

    ..Kerr.. 08/17/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!vKGNG2iSQvhUivvCWxHLbLUvLiERwAW6UGpajjqCGE1cNLjZ8lAjwAb21O2qBhSw7i-0-W7S$=
    for graphic product...


    LAT...LON 34458355 34918266 34188175 33458189 32948238 33708311
    34068367 34458355=20

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