SWOMCD
SPC MCD 221858
MSZ000-LAZ000-ARZ000-222030-
MESOSCALE DISCUSSION 2129
NWS STORM PREDICTION CENTER NORMAN OK
0158 PM CDT MON OCT 22 2007
AREAS AFFECTED...SRN/ERN LA INTO MS
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 221858Z - 222030Z
A GRADUAL INCREASE IN THUNDERSTORM DEVELOPMENT IS EXPECTED THROUGH
THE PEAK AFTERNOON HEATING. TRENDS ARE BEING MONITORED FOR AN
INCREASING SEVERE THREAT AND THE POSSIBILITY OF A WW.
IN A RELATIVELY NARROW PRE-FRONTAL CORRIDOR ACROSS THE LOWER
MISSISSIPPI VALLEY...BREAKS IN CLOUD COVER HAVE ALLOWED SUFFICIENT
SURFACE HEATING TO REDUCE INHIBITION TO NEGLIGIBLE LEVELS. AND
THIS...IN CONJUNCTION WITH LARGE-SCALE FORCING FOR UPWARD VERTICAL
MOTION ASSOCIATED WITH WEAK WARM ADVECTION...APPEARS TO BE
SUPPORTING INCREASING THUNDERSTORM ACTIVITY ACROSS SOUTH CENTRAL
LOUISIANA INTO SOUTHWESTERN MISSISSIPPI. WHILE THIS IS STILL
GENERALLY TO THE NORTH OF EXTENSIVE CONVECTIVE DEVELOPMENT OVER THE
NORTH CENTRAL GULF OF MEXICO INTO CENTRAL GULF COASTAL AREAS...WHICH
IS CUTTING OFF INFLUX OF MID/UPPER 70S F DEW POINTS INTO INLAND
AREAS...DEW POINTS ACROSS THE LOWER MISSISSIPPI VALLEY ARE GENERALLY
IN THE LOWER 70S.
GIVEN AT LEAST MODEST CLOCKWISE-CURVED HODOGRAPHS BENEATH 20-30 KT
SOUTHERLY 850 FLOW...THE BOUNDARY LAYER WITH HIGH MOISTURE CONTENT
AND HIGH RELATIVE HUMIDITIES APPEARS FAVORABLE FOR THE DEVELOPMENT
OF ISOLATED TORNADOES. MIXED LAYER CAPE IS ONLY ON THE ORDER OF 500
J/KG DUE TO WEAK MID-LEVEL LAPSE RATES AHEAD SLOWLY DIGGING UPSTREAM
TROUGH. BUT...DEEP LAYER SHEAR BENEATH 50 KT CYCLONIC 500 MB FLOW
IS STRONG AND FAVORABLE FOR SUPERCELLS...AS ACTIVITY SPREADS NORTH
NORTHEASTWARD THIS AFTERNOON.
.KERR.. 10/22/2007
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MEG...JAN...LIX...LCH...SHV...
30579264 31869182 32789135 33829092 34298981 34238881
32758890 31378989 30389047 29459196
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