SWOD48
SPC AC 300846
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0346 AM CDT THU OCT 30 2008
VALID 021200Z - 071200Z
...DISCUSSION...
LATEST MEDIUM-RANGE GUIDANCE IS IN RELATIVELY GOOD AGREEMENT IN THE
EVOLUTION OF THE LARGE-SCALE PATTERN THROUGH THE EXTENDED PERIOD.
HOWEVER...AS IN PREVIOUS FORECASTS...DIFFERENCES DO EXIST IN THE
DETAILS. AN EMBEDDED SHORT WAVE TROUGH ALONG THE WEST COAST AT THE
ONSET OF THE FORECAST /SUN NOV 2ND/ WILL TRANSLATE EWD THROUGH THE
INTERMOUNTAIN WEST...EVENTUALLY SHIFTING EWD INTO THE NRN AND CNTRL
PLAINS ON D5 /MON NOV 3RD/. DIFFERENCES BEGIN TO APPEAR LATE IN D5
INTO D6 /TUE NOV 4TH/ WHEN THE ECMWF DEVELOPS A SIGNIFICANT SHORT
WAVE TROUGH OVER THE GREAT BASIN BEFORE MOVING INTO THE CNTRL U.S.
ON D7 /WED NOV 5TH/. THE GFS IS SLOWER IN THE DEVELOPMENT OF THIS
FEATURE...BUT DOES EVENTUALLY BECOME SIMILAR TO THE ECMWF BY D8 /THU
NOV 6TH/ WITH THE FORMATION OF A NEGATIVELY-TILTED TROUGH NEAR OR
JUST E OF THE MS VALLEY.
PERSISTENT LOW-LEVEL RIDGING INTO THE GULF OF MEXICO WILL LIKELY
LIMIT MOISTURE RETURN IN ADVANCE OF THE INITIAL SHORT WAVE TROUGH ON
D5 OVER THE PLAINS. AS A RESULT...INSTABILITY AND ANY SEVERE
WEATHER POTENTIAL IS EXPECTED TO BE SMALL. THIS RIDGING OVER THE
GULF IS FORECAST TO WEAKEN WITH THE APPROACH OF THE MORE SUBSTANTIAL
SHORT WAVE TROUGH BY D6. THIS SHOULD ALLOW FOR THE DEVELOPMENT OF A
MORE MOIST AND UNSTABLE WARM SECTOR AIR MASS AND AN INCREASED THREAT
OF ORGANIZED SEVERE WEATHER. HOWEVER...AS MENTIONED
ABOVE...DIFFERENCES DO EXIST IN THE EVOLUTION OF THE UPPER LEVEL
TROUGH AND ATTENDANT FRONTAL SYSTEM. GIVEN THIS UNCERTAINTY...NO
AREA WILL BE DELINEATED.
..MEAD.. 10/30/2008
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