Tuesday, November 15, 2011

MESO: Mesoscale Discussion 2327

ACUS11 KWNS 160300
SWOMCD
SPC MCD 160259
ALZ000-MSZ000-LAZ000-160500-

MESOSCALE DISCUSSION 2327
NWS STORM PREDICTION CENTER NORMAN OK
0859 PM CST TUE NOV 15 2011

AREAS AFFECTED...PORTIONS CENTRAL/SRN LA...SRN MS...SWRN AL.

CONCERNING...TORNADO WATCH 886...

VALID 160259Z - 160500Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 886 CONTINUES.

CONTINUE WW ALONG/AHEAD OF PRIMARY/BKN CONVECTIVE BAND. AREAS E OF
PRESENT WW WILL BE MONITORED FOR PSBL EXTENSION OR ADDITIONAL WW.
COVERAGE OF POTENTIALLY SVR TSTMS WITHIN BROADER CONVECTIVE REGIME
WILL REMAIN ISOLATED AND MRGL FOR WW...BUT SUPERCELL/TORNADO
POTENTIAL CANNOT BE RULED OUT.

MAIN TSTM AREA CONTINUES TO SHIFT ENEWD ACROSS CENTRAL/SRN
LA...EXTENDING AT 230Z FROM ACADIA-VERMILION PARISHES AND THEN SSWWD
OVER COASTAL/OFFSHORE WATERS. SEPARATE CLUSTER OF TSTMS WAS MOVING
NEWD ACROSS WINN/GRANT PARISHES. INITIALLY SEPARATE BAND OF
CONVECTION FROM JUST S MCB SWWD ACROSS BTR MAY MERGE WITH NRN
PORTION OF WRN TSTM BAND. RISK PERSISTS FOR OCNL/EMBEDDED
MESOCYCLONES...BRIEF TORNADOES AND A FEW STG-DAMAGING GUSTS WITH ANY
OF THIS ACTIVITY. SUPERCELL POTENTIAL ALSO EXISTS IN WARM SECTOR
EWD ACROSS DISCUSSION AREA...BUT MORE ISOLATED IN COVERAGE. SVR
POTENTIAL IS LOWER AWAY FROM MAIN CONVECTIVE AREA...BUT NONZERO
GIVEN PRESENCE OF FAVORABLE SHEAR/INSTABILITY THROUGH REMAINDER
EVENING. TSTM COVERAGE E OF PRIMARY ASCENT ZONE WILL BE LIMITED BY
LACK OF ROBUST DEEP-LAYER ASCENT AND LOW-LEVEL BOUNDARIES AS FOCI.
HOWEVER...HIGH MOISTURE THAT CHARACTERIZES NEAR-COASTAL MARINE LAYER
WILL STEM DIABATIC SFC COOLING ENOUGH TO MAINTAIN MINIMAL CINH FOR A
FEW MORE HOURS. RELATIVE POCKET OF DRY AIR WAS ANALYZED OVER
CENTRAL/SRN MS ON 00Z 850-925 MB CHARTS...AND IS MANIFEST AT SFC IN
FORM OF LOW-MID 60S F SFC DEW POINTS AT CBM...MEI...JAN AND PIB.
EXPECT DRY HOLE TO ERODE/MOISTEN FROM S-N AMIDST FAVORABLE LOW-LEVEL
THETAE ADVECTION THROUGH 06Z. MARINE-SECTOR ENVIRONMENT WILL BE
CHARACTERIZED BY MLCAPE GENERALLY AROUND 1500 J/KG AND FAVORABLE
DEEP-LAYER WINDS -- E.G. EFFECTIVE SHEAR MAGNITUDES COMMONLY 50-60
KT. WEAK NEAR-SFC WINDS ARE LIMITING SRH ATTM...ALTHOUGH PROGGED
STRENGTHENING OF LLJ TO AROUND 35 KT BY 06Z SHOULD ENLARGE
HODOGRAPHS ENOUGH TO SUPPORT POTENTIAL FOR ANY RELATIVELY SUSTAINED
DISCRETE CELLS TO ROTATE.

..EDWARDS.. 11/16/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MOB...JAN...LIX...LCH...SHV...

LAT...LON 29559252 30469239 31739255 31839151 31719012 31788806
30588784 30258903 29608990 29159077 29389144 29389114
29559142 29509154 29659163 29379188 29539191 29569217
29559252

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