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Tornado Watch Issued for Texas

10 Nov 2008, 4:04 pm

The Storm Prediction Center has issued a Tornado Watch for central Texas this afternoon, with more likely to follow.

The tornado watch follows the convective outlook updated for this afternoon that calls for afternoon thunderstorms producing large hail with the potential for tornadoes.

Below is this afternoon’s convective outlook:

 DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0153 PM CST MON NOV 10 2008
   
   VALID 102000Z - 111200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN AND TONIGHT ACROSS
   CNTRL/ERN TX INTO PARTS OF THE S CNTRL HIGH PLAINS....
   
   ...SOUTH CENTRAL STATES...
   IN THE WAKE OF THE NORTHERN BRANCH CLOSED LOW/TROUGH LIFTING
   NORTHEAST OF THE GREAT LAKES REGION...A LARGE COLD SURFACE RIDGE IS
   CONFINING SIGNIFICANT BOUNDARY LAYER MOISTENING/DESTABILIZATION
   MAINLY TO AREAS SOUTH OF THE RED RIVER.  THUS...AS THE INITIAL
   STRONGER FORCING LIFTS NORTHEASTWARD LATE THIS AFTERNOON...IN THE
   EXIT REGION OF THE SOUTHWESTERLY MID/UPPER JET STREAK NOSING THROUGH
   THE SOUTHERN HIGH PLAINS...SEVERE POTENTIAL APPEARS LIMITED TO A
   RELATIVELY NARROW CORRIDOR ALONG A DRY LINE FROM PARTS OF NORTHWEST
   TEXAS INTO THE VICINITY OF A DEVELOPING SURFACE LOW OVER SOUTHEAST
   COLORADO.
   
   VERY LATE THIS AFTERNOON...INTO THE EVENING HOURS...IN RESPONSE TO A
   SHORT WAVE IMPULSE PIVOTING THROUGH THE BASE OF THE SOUTHERN BRANCH
   TROUGH...MODELS INDICATE THAT UPPER FLOW WILL BECOME INCREASINGLY
   DIFLUENT/DIVERGENT BETWEEN THE POLAR AND SUBTROPICAL JET AXES ACROSS
   CENTRAL TEXAS.  THIS IS EXPECTED TO CONTRIBUTE TO INCREASING STORM
   DEVELOPMENT IN THE PRESENCE OF A MOISTENING LOW-LEVEL ENVIRONMENT
   WITH STRONG DEEP LAYER SHEAR SUPPORTIVE OF SUPERCELLS.  ALTHOUGH
   LITTLE...IF ANY...MID-LEVEL COOLING MAY OCCUR...AS SURFACE DEW
   POINTS CLIMB THROUGH THE MID/UPPER 60S...BOUNDARY LAYER BASED CAPE
   MAY EXCEED 1000 J/KG...SUPPORTING STRONG UPDRAFTS CAPABLE OF
   PRODUCING LARGE HAIL.  THE CORE OF THE SOUTHERLY LOW-LEVEL JET MAY
   DEVELOP NORTH OF THE UNSTABLE BOUNDARY LAYER...BUT LOW-LEVEL
   HODOGRAPHS NORTH THROUGH NORTHEAST OF THE HILL COUNTRY ARE SILL
   EXPECTED TO REMAIN SIZABLE...ENHANCING THE RISK FOR A COUPLE OF
   TORNADOES...AND LOCALLY DAMAGING WIND GUSTS.
   
   THEREAFTER...UPSCALE DEVELOPMENT INTO ONE OR MORE CONGEALING STORM
   CLUSTERS COULD MAINTAIN A RISK FOR DAMAGING WINDS AND HAIL INTO THE
   OVERNIGHT HOURS ACROSS PARTS OF EAST TEXAS INTO THE SABINE VALLEY 
   ...WHILE NEW STORMS CONTINUE TO BUILD BACK TO THE WEST/SOUTHWEST
   ...TOWARD THE HILL COUNTRY.

Graphics representing the state of the Day 1 Convective Outlook (below left) and Active Warnings and Advisories (below right) at the time of this writing are below.

SPC Convective Outlook HWwarnings

You may wish to view our SPC Convective Outlook, HWwarnings, and HAMrad II product sections to stay informed of updates and developments.

The watch statement is below:


URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 929
   NWS STORM PREDICTION CENTER NORMAN OK
   1225 PM CST MON NOV 10 2008
   
   THE NWS STORM PREDICTION CENTER HAS ISSUED A
   TORNADO WATCH FOR PORTIONS OF 
   
          EXTREME SOUTHWEST OKLAHOMA
          CENTRAL AND NORTHWEST TEXAS
   
   EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 1225 PM UNTIL
   700 PM CST.
   
   TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND
   GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
   AREAS.
   
   THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 65 STATUTE
   MILES EAST AND WEST OF A LINE FROM 20 MILES NORTHWEST OF WICHITA
   FALLS TEXAS TO 40 MILES EAST SOUTHEAST OF JUNCTION TEXAS.  FOR A
   COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
   UPDATE (WOUS64 KWNS WOU9).
   
   REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
   TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS.
   
   DISCUSSION...THUNDERSTORMS ARE BEGINNING TO DEVELOP ACROSS CENTRAL
   TX WHERE LOW-LEVEL MOISTENING AND SURFACE HEATING HAVE ERODED
   CONVECTIVE INHIBITION...AND ADDITIONAL THUNDERSTORM DEVELOPMENT
   APPEARS LIKELY DURING THE AFTERNOON ALONG THE WARM FRONT AND DRYLINE
   NEAR THE RED RIVER IN NW TX.  THOUGH MID LEVEL LAPSE RATES ARE NOT
   PARTICULARLY STEEP AND CLOUDS HAVE LIMITED SURFACE HEATING THUS
   FAR...GRADUAL MOISTENING AND CLOUD BREAKS W OF I-35 SHOULD ALLOW
   SUFFICIENT DESTABILIZATION IN THE WARM SECTOR TO SUPPORT A SEVERE
   STORM THREAT.  MLCAPE VALUES OF 500-1500 J/KG AND STRONG
   LOW-LEVEL/DEEP LAYER SHEAR WILL SUPPORT SUPERCELLS CAPABLE OF
   PRODUCING A FEW TORNADOES...ALONG WITH AT LEAST ISOLATED LARGE HAIL
   AND DAMAGING WINDS.
   
   AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
   SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
   WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
   450. MEAN STORM MOTION VECTOR 25030.
   
   
   ...THOMPSON

cheers,

–patrick

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