Saturday, May 21, 2011

MESO: Mesoscale Discussion 0835

ACUS11 KWNS 211818
SWOMCD
SPC MCD 211818
TXZ000-212015-

MESOSCALE DISCUSSION 0835
NWS STORM PREDICTION CENTER NORMAN OK
0118 PM CDT SAT MAY 21 2011

AREAS AFFECTED...CNTRL TX

CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY

VALID 211818Z - 212015Z

ALTHOUGH TIMING OF TSTM INITIATION REMAINS UNCLEAR...AT LEAST AN
ISOLATED SUPERCELL OR TWO SHOULD FORM ALONG DRYLINE INVOF HILL
COUNTRY THIS AFTERNOON. THERMODYNAMIC ENVIRONMENT WILL BE QUITE
CONDUCIVE TO LARGE HAIL /SOME SIGNIFICANT/ AND WOULD LIKELY REQUIRE
A SEVERE TSTM WATCH ISSUANCE PRIOR TO 20-21Z.

18Z SUBJECTIVE SURFACE ANALYSIS PLACED DRYLINE FROM 40 E SPS S/SSWD
TO NEAR JCT AND DRT. CU FIELD INVOF DRYLINE APPEARS INCREASINGLY
AGITATED OVER THE PAST HOUR ACROSS THE TX HILL COUNTRY. MODIFIED
MORNING RAOBS/RUC FORECAST SOUNDINGS SUGGEST THE AIR MASS IS LARGELY
UNCAPPED AND HAS BECOME VERY UNSTABLE WITH MLCAPE OF 2500 TO 4000
J/KG. DESPITE NEUTRAL UPPER-LEVEL FORCING FOR ASCENT...CONTINUED
HEATING AND MODEST SURFACE CONVERGENCE ALONG THE DRYLINE SHOULD
RESULT IN A FEW TSTMS THIS AFTERNOON /SUPPORTED BY OPERATIONAL AND
CONVECTION-ALLOWING MODEL GUIDANCE/. ALTHOUGH LOW-LEVEL FLOW SHOULD
REMAIN WEAK...35-40 KT WLYS AT 500 MB WILL BE SUFFICIENT FOR
ORGANIZED UPDRAFTS. ISOLATED DISCRETE SUPERCELLS SHOULD YIELD LARGE
HAIL AS THE PRIMARY INITIAL THREAT /SOME OF WHICH MAY BE
SIGNIFICANT/.

..GRAMS.. 05/21/2011

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

ATTN...WFO...FWD...EWX...SJT...

LAT...LON 29990016 30879909 31399864 32269823 32889796 32999731
32619708 32039723 30679794 29849908 29409993 29430023
29670048 29990016

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