Monday, August 25, 2008

Tornado threat resumes



   URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 862
NWS STORM PREDICTION CENTER NORMAN OK
110 AM CDT MON AUG 25 2008

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

SOUTHERN AND CENTRAL ALABAMA
WESTERN PARTS OF THE FLORIDA PANHANDLE
COASTAL WATERS

EFFECTIVE THIS MONDAY MORNING FROM 110 AM UNTIL 900 AM CDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 80 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES WEST NORTHWEST OF
TROY ALABAMA TO 30 MILES SOUTH SOUTHEAST OF PENSACOLA FLORIDA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU2).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

DISCUSSION...TSTMS HAVE BECOME SOMEWHAT BETTER ORGANIZED IN THE PAST
1-2 HRS FROM SW AL S AND SW INTO THE N CNTRL GULF OF MEXICO. THIS
INTENSIFICATION APPEARS TO BE RELATED...IN PART...TO MORE
PROGRESSIVE /EWD/ MOVEMENT THAT HAS BEEN TAKEN ON BY T.D. FAY AND
THE MID LATITUDE VORT MAX WITH WHICH IT MERGED. AS THE LARGE SCALE
CIRCULATION SYSTEM CONTINUES ENEWD...CONVERGENCE SHOULD BECOME MORE
FOCUSED IN ZONE OF RICH GULF INFLOW /SFC DEWPOINTS IN THE MID 70S
F/...BENEATH WEAK COLD ADVECTION ALOFT ALONG THE CNTRL GULF CST.
ASSOCIATED DESTABILIZATION MAY SUPPORT A FEW SUSTAINED UPDRAFTS WITH
LOW LVL ROTATION/ISOLD TORNADOES GIVEN QUALITY OF MOISTURE INFLOW
AND FRICTIONAL/ ISALLOBARICALLY-INDUCED BACKING OF FLOW.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 19035.


...CORFIDI


   MESOSCALE DISCUSSION 2152
NWS STORM PREDICTION CENTER NORMAN OK
0434 AM CDT MON AUG 25 2008

AREAS AFFECTED...PARTS OF CNTRL/SRN AL AND THE WRN FL PANHANDLE

CONCERNING...TORNADO WATCH 862...

VALID 250934Z - 251100Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 862 CONTINUES.

THE SURFACE LOW ASSOCIATED WITH THE REMNANTS OF FAY REMAINS CENTERED
NEAR HATTIESBURG MS...WITH LITTLE NET MOVEMENT DURING THE PAST
SEVERAL HOURS. HOWEVER...MODELS SUGGEST A REDEVELOPMENT NORTH
NORTHEASTWARD TOWARD MERIDIAN MS IS POSSIBLE BETWEEN NOW AND
12-15Z...IN RESPONSE TO THE PROGRESSION OF AT LEAST A COUPLE OF
IMPULSES AROUND THE SOUTHERN/EASTERN PERIPHERY OF THE MID-LEVEL
CIRCULATION.

A LOW-LEVEL CONFLUENCE BAND/SHEAR AXIS ASSOCIATED WITH THE INITIAL
IMPULSE IS IN THE PROCESS OF PIVOTING NORTHWARD THROUGH SOUTHWESTERN
ALABAMA AND THE FAR WESTERN FLORIDA PANHANDLE. EMBEDDED WITHIN A
SLOW EXPANDING AREA OF CONVECTIVE PRECIPITATION...THIS FEATURE
LIKELY WILL REMAIN THE FOCUS FOR SHORT-LIVED INCREASES IN LOW-LEVEL
ROTATION AND POSSIBLE TORNADIC DEVELOPMENT ANOTHER COUPLE OF HOURS.
RUC GUIDANCE SUGGESTS THAT IT WILL BEGIN TO WEAKEN AFTER 12Z AS IT
CONTINUES TO SHIFT INTO WEST CENTRAL ALABAMA. BUT...ANOTHER MAY
DEVELOP/SPREAD FARTHER TO THE EAST ACROSS SOUTHERN ALABAMA AND THE
WESTERN FLORIDA PANHANDLE ...ASSOCIATED WITH THE NEXT IMPULSE.

WITH EASTWARD EXTENT AWAY FROM THE SURFACE LOW CENTER...AND A 30-40
KT LOW-LEVEL JET CORE TO ITS IMMEDIATE EAST...LOW-LEVEL SHEAR
WEAKENS CONSIDERABLY. HOWEVER...GIVEN THE CONTINUING PRESENCE OF A
MOIST BOUNDARY LAYER CHARACTERIZED BY LOWER/MID 70S DEW
POINTS...LOW- LEVEL HODOGRAPHS ALONG AN EFFECTIVE WARM FRONT NEAR OR
JUST NORTH OF THE FLORIDA/ALABAMA BORDER COULD BE SUFFICIENT FOR
SHORT-LIVED TORNADOES IN DISCRETE CELLS WHICH MAY CONTINUE TO
DEVELOP ACROSS THE REGION INTO MID MORNING.

..KERR.. 08/25/2008

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