Saturday, May 10, 2008

New meso discussion


   MESOSCALE DISCUSSION 0874
NWS STORM PREDICTION CENTER NORMAN OK
0921 PM CDT SAT MAY 10 2008

AREAS AFFECTED...NERN AR...WRN/MIDDLE TN...NRN AL...NRN MS

CONCERNING...TORNADO WATCH 298...300...

VALID 110221Z - 110345Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 298...300...CONTINUES.

LATEST MESOANALYSIS DEPICTS A WARM FRONT EXTENDING SE FROM THE
MID-SOUTH INTO THE TN VLY AT 02Z. SOUTH OF THE FRONT...THE BOUNDARY
LAYER CONTINUED TO MOISTEN/DESTABILIZE WITH LWR 70S DEW POINTS NOW
OBSERVED AS FAR N AS THE TN/MS BORDER AND INTO NWRN AL. THIS WAS
CONTRIBUTING TO MLCAPES OF 2000-2500 J/KG.

VWP FROM HIGH TOP AL AND COLUMBUS MS SHOW A STRONGLY SHEARED 0-6KM
LAYER WITH VALUES AOA 60 KTS. GIVEN MAGNITUDE OF MID-LEVEL LAPSE
RATES/INSTABILITY PRESENT...THERE IS NO SURPRISE AT THE WELL-
MAINTAINED LARGE SUPERCELL TSTMS OVER MIDDLE TN SWWD INTO NWRN MS AT
MID-EVENING.

SUPERCELL STRUCTURES WILL CONTINUE TO BE POSSIBLE THROUGH LATE
EVENING DOWNSTREAM INTO NRN MS...SRN MIDDLE TN AND NRN AL.
BUT...NUMBER OF STORMS DEVELOPING WITHIN THE INCREASING WARM
ADVECTION PROFILE MAY JUMP-START AN EVOLUTION INTO BOW
ECHOES/DERECHO. THUS...ALONG WITH TORNADO POTENTIAL...DMGG WIND
GUSTS WILL ALSO BE LIKELY...WITH SOME WIND GUSTS IN EXCESS OF 65
KTS. MAIN ACTIVITY WILL REACH NERN MS/NWRN AL BY 04Z...WITH STORMS
DEVELOPING SEWD INVOF THE WARM FRONT BEFORE THEN.

MEANWHILE...UPSTREAM WITHIN WRN PARTS OF TORNADO WATCH 298...TSTMS
JUST UPSTREAM ACROSS NCNTRL AR APPEAR TO BE WEAKENING AS THEY INGEST
RAIN-COOLED PARCELS FROM THE LEADING STORMS IN THE TN VLY/MID-SOUTH.
THIS WEAKENING TREND IS EXPECTED TO CONTINUE AS THE LLJ BEGINS TO
VEER INTO NRN MS/MIDDLE TN REGION WITH TIME THIS EVENING.

..RACY.. 05/11/2008

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