SWOMCD
SPC MCD 241511
GAZ000-ALZ000-241715-
MESOSCALE DISCUSSION 2147
NWS STORM PREDICTION CENTER NORMAN OK
1011 AM CDT SUN AUG 24 2008
AREAS AFFECTED...PORTIONS AL...EXTREME SWRN GA.
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 241511Z - 241715Z
BRIEF/SPORADIC SUPERCELLS MAY DEVELOP WITH OUTER BANDS REVOLVING
AROUND REMAINS OF TS FAY. TORNADO POTENTIAL IS WEAK/MRGL ATTM BUT
MAY INCREASE THROUGH MID-LATE AFTERNOON.
SFC ANALYSIS SHOWS DIFFUSE LOW OVER SERN MS BETWEEN PIB-MEI...WITH
WEAK CENTRAL WINDS AND FILLING PRESSURE AS CIRCULATION OF FAY
CONTINUES TO WEAKEN. LOW-MIDLEVEL REMAINS OF TS FAY HAVE BECOME
INTERMINGLED WITH PRE-EXISTING MID-UPPER LEVEL LOW THAT PIVOTED
SWD/SEWD ACROSS AR AND LA YESTERDAY AFTERNOON AND OVERNIGHT.
MOISTURE CHANNEL IMAGERY AND 12Z BMX/TLH RAOBS INDICATE PRONOUNCED
DRYING ALOFT FROM THAT UPPER PERTURBATION NOW WRAPPING AROUND ERN
PORTION OF COMBINED CIRCULATION. STRONGEST DRYING APPEARS CLOSER TO
CENTER AS ALSO EVIDENT IN GPS PW DATA...WHICH SHOWS VALUES OF
1.7-1.8 INCH FROM MOUTH OF MS RIVER NEWD ACROSS MOB AREA THEN NWD
INTO CENTRAL AL...AND PRONOUNCED DROP IN PW LAST FEW HOURS BETWEEN
MOB-BHM. RELATIVELY MOIST LOW LEVEL PLUME IS EVIDENT FARTHER E
ACROSS ERN AL...WRN GA AND FL PANHANDLE...WHICH SHOULD SUPPORT
CONVECTION POTENTIAL AS IT SHIFTS SLOWLY WWD IN STEP WITH
TRANSLATIONAL MOTION OF BROADER CIRCULATION. WHILE DRY SLOT REDUCED
POTENTIAL CONVECTIVE COVERAGE CLOSER TO CENTER...IT IS SUPPORTING
CONSIDERABLE BREAKS IN CLOUDS ACROSS MUCH OF SRN/CENTRAL AL THAT
EXTEND EWD OVER BOUNDARY LAYER MOISTURE PLUME. CONTINUED INSOLATION
IN BETWEEN EXISTING CONVECTIVE BANDS MAY OFFSET VERY WEAK MID-UPPER
LEVEL LAPSE RATES ENOUGH TO DEVELOP MLCAPE 250-500 J/KG OVER
PORTIONS CENTRAL AL DURING NEXT FEW HOURS...INCREASING TO 1000 J/KG
NEAR SRN PORTION AL/GA LINE. STRENGTHENING INSTABILITY WILL
COINCIDE WITH WEAKENING OF LOW LEVEL SHEAR...A TREND ALREADY EVIDENT
IN DECREASE OF SELY NOCTURNAL LLJ FROM VWP SITES OVER SERN AND
CENTRAL AL. HOWEVER...FCST SOUNDINGS SUGGEST HODOGRAPH SIZE STILL
WILL BE SUFFICIENT TO SUPPORT SUPERCELLS...ESPECIALLY FROM E-CENTRAL
AL NWWD ACROSS CENTRAL AL WHERE SFC FLOW IS MOST STRONGLY
BACKED...WITH 0-1 KM SRH 200-400 J/KG PERSISTING INTO AT LEAST
MID-AFTERNOON.
..EDWARDS.. 08/24/2008
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...FFC...TAE...BMX...HUN...MOB...
31438652 31948680 32588715 33308808 33668821 34148763
33908654 33548552 32768485 31848483 31238490 31088556
31188638
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