SWODY1
SPC AC 091957
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT SUN OCT 09 2011
VALID 092000Z - 101200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
BOTH LOW-PROBABILITY SEVERE THREAT AREAS ARE BEING REMOVED THIS
FORECAST...AS CURRENT TRENDS SUGGEST DECREASING SEVERE POTENTIAL IN
GENERAL OVER THE NEXT SEVERAL HOURS.
IN S TX...AN OUTFLOW BOUNDARY IS PRESSING SEWD AND WILL CONTINUE
MOVING BOTH OFFSHORE AND INTO FAR NERN MEXICO. THOUGH A ISOLATED/
MARGINAL HAIL OR WIND EVENT MAY OCCUR WITHIN THE NEXT HOUR...EXPECT
A CONTINUED DOWNWARD TREND IN POTENTIAL THUS WARRANTING REMOVAL OF
PROBABILITIES.
IN FL...A LARGE AREA OF STEADY/WIDESPREAD RAINFALL WITH EMBEDDED
CONVECTION IS DRIFTING NWWD JUST OFF THE E COAST OF FL...WITH
SUBSIDENCE SUPPRESSING CELLULAR CONVECTION JUST WEST OF THIS SYSTEM
INTO E CENTRAL FL -- WHERE LOW PROBABILITY TORNADO THREAT WAS
INCLUDED IN PRIOR FORECASTS. WITH THREAT THUS DIMINISHING
HERE...AND ONLY VERY LOW PROBABILITY POTENTIAL FOR A BRIEF/WEAK
TORNADIC SPIN-UP AT BEST EVIDENT FARTHER NWD INTO NERN FL AND
VICINITY...WILL OPT TO REMOVE THE THREAT AREA ATTM.
..GOSS.. 10/09/2011
.PREV DISCUSSION... /ISSUED 1120 AM CDT SUN OCT 09 2011/
...DEEP S TX TO ALONG THE MIDDLE TX COAST...
12Z SOUNDINGS INDICATE THAT INFLOW AIR MASS TO ONGOING STORMS IS
QUITE MOIST WITH PW VALUES OF 1.8-1.9 INCHES. DAYTIME HEATING
COUPLED WITH THE MOIST ENVIRONMENT WILL YIELD MODERATE INSTABILITY
BY AFTERNOON WITH MLCAPE OF 1500-2500 J/KG. WHILE DEEP-LAYER WIND
FIELD WILL GRADUALLY DIMINISH THROUGH THE DAY AS MIDLEVEL TROUGH
LIFTS NEWD AWAY FROM THE REGION...THE DEGREE OF INSTABILITY AND HIGH
MOISTURE CONTENT WILL SUPPORT LOCALLY DAMAGING WET MICROBURSTS WITH
STRONGER/LONGER-LIVED STORM CLUSTERS.
OVER THE MIDDLE TX COAST...CURRENT VAD DATA FROM HOUSTON INDICATE A
VERTICALLY VEERING WIND PROFILE WITH 0-1 KM SRH OF AROUND 150 M2/S2.
DEEP-LAYER SHEAR IS WEAK...BUT GIVEN THE COMBINATION OF A
MOIST/LOW-LCL BOUNDARY LAYER...MODEST LOW-LEVEL SHEAR AND POTENTIAL
FOR OUTFLOW BOUNDARY-SEA BREEZE INTERACTIONS...A LOW RISK FOR A
BRIEF TORNADO WILL EXIST.
...CNTRL/SRN FL PENINSULA...
VISIBLE SATELLITE IMAGERY SHOWS A COUPLE OF CYCLONIC CIRCULATIONS...
ONE JUST N OF GRAND BAHAMA AND THE OTHER ASSOCIATED WITH A
DEEPER-LAYER CIRCULATION WSW OF APF. LATEST MODEL GUIDANCE SUGGESTS
THAT THE FORMER WILL DEVELOP WWD...EVENTUALLY MERGING WITH THE
LATTER THIS FORECAST PERIOD. THIS WILL RESULT IN A CORRIDOR OF
ENHANCED LOW-LEVEL CONVERGENCE ALONG THE E-CNTRL PENINSULA THIS
AFTERNOON WHERE A MOIST/UNSTABLE AIR MASS WILL ALIGN WITH A CHANNEL
OF STRONGER LOW-LEVEL FLOW. AS SUCH...A SMALL RISK FOR LOCALLY
DAMAGING WIND GUSTS AND PERHAPS A BRIEF TORNADO WILL EXIST WITH ANY
STORMS THAT DEVELOP.
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