SWODY1
SPC AC 281630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT WED OCT 28 2009
VALID 281630Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE SRN
PLAINS...
...SYNOPSIS...
DEEP AND CLOSED UPPER LOW LOCATED IN THE UT/AZ AREA THIS MORNING IS
FORECAST TO SHIFT EWD INTO NM TONIGHT...AS STRONGER WINDS ALOFT
DEVELOP OVER THE CENTRAL/SRN HIGH PLAINS...IN RESPONSE TO
STRENGTHENING GRADIENT ALOFT. COMPLEX AREA OF SURFACE LOW PRESSURE
IS CURRENTLY LOCATED OVER THE CENTRAL/SRN ROCKIES. HOWEVER... MODELS
ARE CONSISTENT IN THE MAIN SURFACE LOW MOVING/DEVELOPING I THE LBB
AREA THIS EVENING...AND THEN ACCELERATING RAPIDLY NEWD INTO ERN KS
BY THU MORNING...AHEAD OF EVOLVING WIND MAX ALOFT. PRIMARY CONCERN
FOR SEVERE CONVECTION IS EXPECTED ALONG AND AHEAD OF DEEPENING
SURFACE LOW AND SWD TRAILING COLD FRONT.
...SRN PLAINS...
LATEST SATELLITE PW DATA AND PUSH OF MID/UPPER 60 DEWPOINTS INTO SRN
TX INDICATES RAPID MOISTURE ADVECTION IS ALREADY UNDERWAY...AND
SHOULD CONTINUE NWD ACROSS MUCH OF TX AND OK INTO THE OVERNIGHT
HOURS. STRONG CAPPING AND WEAK FORCING SHOULD LIMIT CONVECTIVE
DEVELOPMENT THROUGH MOST OR ALL OF THE DAYLIGHT HOURS ACROSS THE
SLIGHT RISK AREA. HOWEVER...THE COMBINATION OF LARGE SCALE FORCING
SPREADING IN FROM THE WEST...INCREASING MOISTURE/INSTABILITY AND LOW
LEVEL CONVERGENCE SHOULD LEAD TO THE DEVELOPMENT OF STRONG STORMS
ALONG AND EAST OF SURFACE LOW/FRONT ACROSS THE SRN HIGH PLAINS THIS
EVENING. STRONG MOSTLY SSWLY UNIDIRECTIONAL WINDS ALOFT SUGGEST THE
STORMS ARE LIKELY TO EVOLVE RAPIDLY INTO A SQUALL LINE AND SHIFT
QUICKLY EWD OVERNIGHT. DESPITE RELATIVELY WEAK LOW LEVEL LAPSE
RATES...MUCAPES FROM 500 TO 1000 J/KG ALONG WITH STRENGTHENING DEEP
SSWLY WIND FIELDS...AND 700 MB SPEEDS AOA 50 KT FAVORS DAMAGING
WINDS AS THE PRIMARY THREAT. HOWEVER...DEEP LAYER SHEAR AT 50 TO 60
KT AND STRONGLY CURVED LOW LEVEL HODOGRAPHS...1 KM SHEAR AROUND 40
KT...INDICATES TORNADOES WOULD ALSO BE POSSIBLE WITH EMBEDDED
BOWS/LEWPS AND ANY DISCRETE CELLS THAT DEVELOP AHEAD OF THE SQUALL
LINE.
...SERN TX AND SWRN LA...
A SEPARATE AREA OF LOW PROBABILISTIC SEVERE THREAT WILL EXIST AFTER
06-09Z AS MODELS SUGGEST CONVECTION DEVELOPING ALONG WARM FRONT
LIFTING NEWD ACROSS SERN TX AND SWRN LA. IT APPEARS THESE STORMS
WILL TAKE TIME TO STRENGTHEN AND ARE MORE LIKELY TO BECOME SEVERE
AFTER 12Z...AS STRONGER FORCING ALOFT OVERSPREADS THE AREA AND
RESULTS IN A MORE FAVORABLE ENVIRONMENT FOR SEVERE STORMS.
..IMY/JEWELL.. 10/28/2009
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