• MESO: Mesoscale Discussion 0151

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Feb 15 23:42:03 2023
    ACUS11 KWNS 152341
    SWOMCD
    SPC MCD 152341=20
    MSZ000-TNZ000-ARZ000-LAZ000-160245-

    Mesoscale Discussion 0151
    NWS Storm Prediction Center Norman OK
    0541 PM CST Wed Feb 15 2023

    Areas affected...parts of central and northern Louisiana and Mississippi...southeastern Arkansas...southwestern Tennessee

    Concerning...Severe potential...Watch possible=20

    Valid 152341Z - 160245Z

    Probability of Watch Issuance...60 percent

    SUMMARY...There appears some potential for isolated supercells
    capable of producing tornadoes in a corridor across central
    Louisiana through central Mississippi into this evening. More
    widespread thunderstorm development with increasing severe weather
    potential appears more probable in a corridor from northern
    Louisiana into northern Mississippi and adjacent portions of the
    lower Mississippi Valley during the 8-11 PM CST time frame.

    DISCUSSION...A weakness in mid-level inhibition around the 700 mb
    level appears to be allowing for the initiation of scattered
    thunderstorms in a corridor roughly from Alexandria, LA through the
    Jackson, MS area, where warm sector boundary-layer destabilization
    is peaking. Objective analysis suggests that CAPE may range from
    1000-2000 J/kg, in the presence of strong deep layer shear beneath
    40-50 kt west-southwesterly flow around 500 mb. Beneath southerly
    850 mb flow around 30+ kt, low-level hodographs appear moderately
    large and clockwise curved. This environment appears potentially
    conducive to supercell development with a risk for tornadoes during
    the next hour or two. However, it remains unclear if this initial
    convection will be sustained after dark, once near-surface cooling
    increases convective inhibition.

    There appears better potential for new thunderstorm activity to
    initiate along a corridor farther to the north, roughly across parts
    of northern Louisiana, southeastern Arkansas and northern
    Mississippi, coincident with a strengthening south-southwesterly
    low-level jet (40-50 kt around 850 mb) through the 02-05Z time
    frame. This may be aided by forcing associated with strengthening
    divergence aloft, between coupled upper-level speed maxima migrating
    around the periphery of the subtropical ridge centered over the Caribbean/Bahamas.

    ..Kerr/Guyer.. 02/15/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7jR0xJAfMV4SmIQNjWSk6PBdLXVr9ZRj3dcTIl6-HaL6pxzAuU6C8w0MVD_-2gTOulBvhwiQs= 3hU1HBxvBbJfgc2-MM$ for graphic product...

    ATTN...WFO...MEG...JAN...LIX...LZK...LCH...SHV...

    LAT...LON 33009370 34039253 34629127 35228947 33608879 32388901
    32148973 31199157 31129301 33009370=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun Feb 18 15:19:16 2024
    ACUS11 KWNS 181519
    SWOMCD
    SPC MCD 181518=20
    FLZ000-181715-

    Mesoscale Discussion 0151
    NWS Storm Prediction Center Norman OK
    0918 AM CST Sun Feb 18 2024

    Areas affected...FL Keys and extreme south FL Peninsula

    Concerning...Severe potential...Watch unlikely=20

    Valid 181518Z - 181715Z

    Probability of Watch Issuance...20 percent

    SUMMARY...A tornado and localized damaging wind swath will be
    possible as a short-line segment spreads across the Keys and extreme
    south Florida into early afternoon.

    DISCUSSION...A thin and short-line segment is apparent near the Dry
    Tortugas into the FL Straits, within a low-level warm theta-e
    advection regime. The north portion of this segment has shown
    storm-scale organization, with broad rotation and comma-head
    reflectivity structure. This appears to be near/along the
    quasi-stationary front that is draped between the Keys and the
    Everglades, east through about Key Largo. 12Z guidance suggest this
    boundary will attempt to advance north into early afternoon across
    south portions of mainland Monroe and Miami-Dade counties. It is
    plausible that the organizational structure of the short-line
    segment may be maintained east along the baroclinic zone with an
    embedded tornado and severe wind threat. Background environment does
    have limiting factors such as very poor mid-level lapse rates
    (700-500 mb from 4.5 to 5 C/km per 12Z Key West and Miami soundings)
    and minimal change in wind speeds between 1 to 3 km AGL. This
    suggests that any severe threat will be quite localized and focused
    along the surface front.

    ..Grams/Hart.. 02/18/2024

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!4A8BOEELXfTIA_XI0wT2Y1zMhSWrTbbV-neuHV8_9ZY1nf0FSYr4Rh316PL8XhpTIMXY6NPoz= Yg1qwAQ9fAujxaONqk$ for graphic product...

    ATTN...WFO...MFL...KEY...

    LAT...LON 25028199 25508096 25868017 25767997 25387996 24618093
    24268232 24908223 25028199=20


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