SWODY2
SPC AC 081736
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1236 PM CDT WED APR 08 2009
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OZARKS REGION TO NE TX
AND LOWER MS VALLEY...
...SYNOPSIS...
IN MID-UPPER LEVELS...PROGRESSIVE SHORTWAVE PATTERN OF CONSIDERABLE
AMPLITUDE IS FCST THROUGH PERIOD. UPPER CYCLONE INITIALLY COVERS
NRN PORTIONS CA/NV. THIS FEATURE CONTAINS TWO PRIMARY MID-UPPER
LEVEL VORTICITY LOBES...ONE OVER NWRN CA NEAR SFO...AND ONE OVER
NERN NV...BASED ON LATEST VWP DATA AND MOISTURE CHANNEL IMAGERY.
THESE LOBES ARE FCST TO SPREAD APART...WITH NV VORTICITY CENTER
MOVING ENEWD OVER WY AND WEAKENING THROUGH PERIOD. MEANWHILE...CA
SEGMENT SHOULD PIVOT SEWD TO NM AS COMPACT/STG SHORTWAVE TROUGH BY
9/12Z...MOVING NEWD ACROSS TX PANHANDLE AND SWRN KS/NWRN OK AREA
MID-DAY THURSDAY...THEN FORMING CLOSED 500 MB CYCLONE OVER ERN KS BY
10/06Z.
AT SFC...LEE TROUGHING NOW DEVELOPING OVER CENTRAL/SRN HIGH PLAINS
WILL INTENSIFY THROUGH BEGINNING OF PERIOD AS MID-UPPER TROUGH
APCHS. BY 9/12Z...DEEPENING SFC LOW SHOULD BE LOCATED INVOF NWRN
OK...WITH WARM FRONT ESEWD OVER NRN OK AND SEWD THROUGH ARKLATEX
REGION. SFC CYCLONE SHOULD MOVE GENERALLY EWD ACROSS NRN OK THEN
NEWD TOWARD ERN PORTION KS/OK BORDER BY 10/00Z...WARM FRONT ESEWD
ACROSS OZARKS TO WRN TN...COLD FRONT SWWD OVER WRN OK. LOW SHOULD
REACH PORTIONS CENTRAL/SERN MO BY END OF PERIOD...WITH COLD FRONT
OVER CENTRAL AR AND PORTIONS CENTRAL/SW TX.
DRYLINE IS EXPECTED TO BECOME BETTER DEFINED THROUGH EARLY PERIOD
ALONG W EDGE OF MOISTURE RETURN PROCESS DISCUSSED BELOW. DRYLINE
SHOULD MIX AND ADVECT EWD ACROSS MOST OF OK AND N-CENTRAL/CENTRAL TX
DURING AFTERNOON. BY 00Z...DRYLINE IS FCST FROM NERN OK SSWWD
ACROSS ERN OK -- ALONG OR E OF US-69 CORRIDOR -- SSWWD TO
MIDDLE-LOWER TX COASTAL PLAIN AND LOWER RIO GRANDE VALLEY.
OPERATIONAL NAM/SPECTRAL...EACH OFTEN SLIGHTLY TOO FAR E WITH FCST
DRYLINE POSITIONS...ARE SUPPORTED BY STG CONSENSUS OF 09Z SREF
MEMBERS.
...OZARKS REGION TO NE TX AND LOWER MS VALLEY...
MOST IMPORTANT FACTOR FOR SVR POTENTIAL WILL BE QUALITY OF MOISTURE
THROUGHOUT RETURN-FLOW BOUNDARY LAYER. STG COLD FROPA HAS
PENETRATED THROUGH ENTIRE GULF AND WELL INTO CENTRAL AMERICA AND
CARIBBEAN. NEAREST MARITIME/TROPICAL AIR MASS CONTAINING UPPER 60S
F SFC DEW POINTS IS ANALYZED OVER MEX PAC COAST AND ISTHMUS OF
TEHUANTEPEC ATTM...TOO FAR TO BE INCORPORATED INTO MOIST SECTOR OF
DAY-2 SYSTEM. NARROW PLUME OF VIGOROUS MARINE MODIFICATION IS
UNDERWAY FROM BAY OF CAMPECHE NWD TO OFFSHORE LOWER TX COAST...WITH
MID 50S AND SPOTTY LOW 60S F DEW POINTS EVIDENT. CENTRAL/WRN
OPEN-GULF SST SUPPORTS EQUILIBRIUM DEW POINTS GENERALLY 64-68 DEG
F...THOUGH DIURNAL/VERTICAL MIXING SHOULD REDUCE THESE VALUES WELL
INLAND FROM TX COAST. UPSTREAM BOUNDARY LAYER ALSO APPEARS RATHER
SHALLOW BASED ON MORNING BRO/MERIDA SOUNDINGS...AND LARGE AREA OF
MID-UPPER SUBSIDENCE EVIDENT IN MOISTURE CHANNEL IMAGERY OVER MOST
OF GULF. ACCORDINGLY...PRIND OPERATIONAL NAM...ETA-KF AND
ESPECIALLY ETA-BMJ MEMBERS OF SREF ARE TOO AGGRESSIVE WITH MOISTURE
RETURN. PRIND DEW POINTS SHOULD REACH MAINLY 50S E OF DRYLINE IN
OK BY 21Z...LOW 60S FROM SERN OK OVER MOST OF CENTRAL/ERN
TX...BENEATH STRONG ELEVATED MIXED-LAYER AND RELATED CAPPING.
MOISTURE SHOULD INCREASE CONSIDERABLY AFTER DARK AND JUST ABOVE
SFC...IN NARROW PLUME PRECEDING COLD FRONT AND DRYLINE.
SCATTERED TSTMS SHOULD INITIATE MID-DAY TO MID-AFTERNOON IMMEDIATELY
AHEAD OF SFC CYCLONE TRACK WHERE DEEP-LAYER ASCENT AND
LOW-LEVEL/CONVECTIVE SCALE FORCING WILL BE STRONGEST. ACTIVITY
SHOULD MOVE/EXPAND EWD THROUGH PERIOD ACROSS OZARKS REGION...WITH
SOME SWD BACKBUILDING INVOF COLD FRONT/DRYLINE AS STG CAP IS
OVERCOME LATE AFTERNOON INTO EARLY EVENING. UNCONDITIONAL SVR
POTENTIAL APPEARS GREATEST FROM VICINITY KS/OK BORDER EWD OVER
OZARKS...WITH CONVECTIVE COVERAGE AND SVR THREAT BECOMING MORE
UNCERTAIN WITH SWD EXTENT OVER ARKLATEX REGION AND E TX.
VERTICAL SHEAR PROFILES WILL BE FAVORABLE FOR SUPERCELLS OVER WIDE
AREA...WITH LARGE LOW LEVEL HODOGRAPHS...0-1 KM SRH AOA 200
J/KG...AND EFFECTIVE SHEAR MAGNITUDES AOB 50 KT COMMON OVER MUCH OF
MOIST SECTOR. FCST SFC HEATING...STEEP LAPSE RATES AND DEEP BUOYANT
PROFILES INDICATE MLCAPE EXCEEDING 1500 J/KG EVEN WITH MORE MODEST
MOISTURE RETURN. POTENTIAL FOR DAMAGING HAIL EXISTS WITH ANY
SUSTAINED AND RELATIVELY DISCRETE STORMS. TORNADO THREAT MAY
DEVELOP INVOF SFC WARM FRONT DURING AFTERNOON...WHERE LOW LEVEL
VORTICITY AND BACKED SFC WINDS EACH WILL BE MOST PRONOUNCED.
FARTHER S ALONG/AHEAD OF DRYLINE...TORNADO THREAT APPEARS FAR MORE
CONDITIONAL...ESPECIALLY GIVEN SOMEWHAT HIGH DIURNAL LCL. SOME
TORNADO THREAT MAY BE CONCENTRATED BETWEEN OZARKS AND ARKLATEX
DURING A FEW EVENING HOURS WHEN LCL LOWERS DUE TO COMBINATION OF SFC
COOLING AND MOIST ADVECTION...YET COOLING IS NOT YET TOO STG TO KEEP
EFFECTIVE LIFTED PARCELS ROOTED AT SFC.
..EDWARDS.. 04/08/2009
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