SWOD48
SPC AC 150949
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0349 AM CST THU DEC 15 2011
VALID 181200Z - 231200Z
...POTENTIAL FOR A REGIONAL SVR TSTM EVENT STILL APPEARS LOW...
MEDIUM RANGE FORECAST GUIDANCE INDICATES A STRENGTHENING WESTERLY
COMPONENT WITHIN THE SOUTHERN BRANCH OF THE SPLIT FLOW EMERGING FROM
THE PACIFIC LATE THIS COMING WEEKEND INTO EARLY NEXT WEEK. AS THIS
OCCURS...THE CUT-OFF LOW NEAR THE SOUTHWESTERN U.S. INTERNATIONAL
BORDER SHOULD BEGIN ACCELERATING EASTWARD. THE 15/00Z ECMWF AND GFS
ARE NOW IN MUCH BETTER AGREEMENT WITH THIS FEATURE PROGRESSING EAST
OF THE SOUTHERN ROCKIES DURING THE DAY MONDAY...BEFORE CONTINUING
ACROSS THE SOUTH CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY
BY EARLY WEDNESDAY. HOWEVER... CONSIDERABLE SPREAD LINGERS AMONG
THE MODEL ENSEMBLE DATA CONCERNING THIS DEVELOPMENT...AND
VARIABILITY ALSO EXISTS CONCERNING LOW-LEVEL CYCLOGENESIS ACROSS THE
SOUTH CENTRAL STATES.
MOST OF THE GUIDANCE...THOUGH...IS SUGGESTIVE THAT CYCLOGENESIS WILL
NOT BECOME PARTICULARLY STRONG...WITH LOWEST SURFACE PRESSURES
GENERALLY FORECAST TO REMAIN ABOVE 1000 MB. WHILE DEEP LAYER FLOW
FIELDS AND VERTICAL SHEAR LIKELY WILL BECOME SUPPORTIVE OF SEVERE
POTENTIAL IN THE WARM SECTOR...CONCERN EXISTS THAT LARGE-SCALE
FORCING FOR UPWARD VERTICAL MOTION AND LOW-LEVEL MOISTURE RETURN MAY
REMAIN WEAK TO MODEST IN STRENGTH...LIMITING DESTABILIZATION AND THE
SCOPE OF THE SEVERE THREAT. BUT THIS COULD STILL INCLUDE THE RISK
FOR AT LEAST LOCALIZED OR SPORADIC DAMAGING WIND GUSTS...AND
POTENTIAL FOR ISOLATED TORNADOES... ACROSS PARTS OF THE SOUTHERN
PLAINS INTO THE LOWER MISSISSIPPI VALLEY/CENTRAL GULF COAST STATES
LATE MONDAY INTO EARLY NEXT WEDNESDAY.
..KERR.. 12/15/2011
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