SWOMCD
SPC MCD 050435
FLZ000-ALZ000-MSZ000-LAZ000-050630-
MESOSCALE DISCUSSION 2128
NWS STORM PREDICTION CENTER NORMAN OK
1135 PM CDT SUN SEP 04 2011
AREAS AFFECTED...PORTIONS SERN LA...CENTRAL/SRN MS...CENTRAL/SRN
AL...WRN FL PANHANDLE.
CONCERNING...TORNADO WATCH 837...
VALID 050435Z - 050630Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 837 CONTINUES.
RELATIVELY MAXIMIZED TORNADO POTENTIAL MAY BE SHIFTING
INLAND...RESULTING FROM SECTORIZED EVOLUTION UNDERWAY IN LOW-LEVEL
STRUCTURE OF WIND/THETAE FIELDS AROUND ERN SEMICIRCLE OF T.D. LEE.
04Z SFC MESOANALYSIS INDICATED CENTER OF CIRCULATION DRIFTING
ERRATICALLY BETWEEN BTR-LFT. LONGSTANDING SPIRAL BAND SE THROUGH S
OF CENTER HAS LOST MOST OF ITS DEEP CONVECTION BUT STILL STANDS OUT
WELL IN STREAMLINE ANALYSIS AS CONFLUENCE LINE...EXTENDING OFFSHORE
FROM ERN TERREBONNE PARISH. VEERING FLOW ALONG AND W OF THIS
BOUNDARY WILL REDUCE SRH SUBSTANTIALLY...WITH LITTLE SIGNIFICANT
CONVECTION EXPECTED. ANY PARTS OF THAT SECTOR THAT MOVE OVER WRN
PORTIONS WW OVERNIGHT...IN STEP WITH FCST EWD TO NEWD TRANSLATIONAL
MOTION OF LEE...MAY BE CLEARED FROM WW. INCREASINGLY PRONOUNCED
CONFLUENCE AXIS EXTENDS NEWD FROM CENTER TO BETWEEN MCB-JAN AND OVER
CBM...COLLOCATED WITH THETAE AND BUOYANCY GRADIENT. NW OF THIS
BOUNDARY...CAPE DIMINISHES TO NEAR ZERO BENEATH PERSISTENTLY
RAIN-COOLED AIR. FARTHER S...MORE SUBTLE CONFLUENCE LINE IS DRAWN
FROM FRANKLIN COUNTY MS EWD TO NEAR PIB THEN CURVING SEWD ACROSS PNS
AREA. RELATIVELY BACKED SFC WINDS AND LARGEST LOW-LEVEL HODOGRAPHS
SHOULD REMAIN BETWEEN THIS AND NRN CONFLUENCE LINE...ALONG WITH AT
LEAST MRGL BUOYANCY...I.E. EFFECTIVE SRH 200-400 J/KG AND MLCAPE
250-600 J/KG RESPECTIVELY. SUPERCELLS IN BETWEEN THESE TWO
CONFLUENCE LINES...AND CROSSING NRN BOUNDARY...WILL POSE GREATEST
TORNADO THREAT.
ALTHOUGH LARGEST CAPE IS OVER COASTAL AREAS FROM BVE-PFN...AND
SHOULD REMAIN SO...LACK OF CONVERGENCE IN SERN SECTOR OF SYSTEM MAY
LIMIT CONVECTIVE COVERAGE/MAINTENANCE THERE...RENDERING TORNADO
THREAT LESS THAN THAT FARTHER INLAND -- ALBEIT STILL NONZERO.
..EDWARDS.. 09/05/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...TAE...BMX...MOB...JAN...LIX...
LAT...LON 29119053 30379021 31179035 31679066 33108868 32638756
31298625 30368643 30278745 30228874 30128916 30028884
29788882 29468914 29388925 29198897 28988913 29078926
28878948 29098936 29298978 29079026 29119053
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