MESOSCALE DISCUSSION 1785
   NWS STORM PREDICTION CENTER NORMAN OK
   0313 PM CDT FRI JUL 29 2011
   
   AREAS AFFECTED...PORTIONS COASTAL S TX.
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 292013Z - 292245Z
   
   TORNADO POTENTIAL...WHILE INITIALLY QUITE MRGL...MAY INCREASE DURING
   REMAINDER AFTERNOON AND EVENING ALONG PORTIONS TX COAST AS CENTER OF
   TS DON NEARS PROJECTED LANDFALL.
   
   PER NHC FCSTS...CENTER SHOULD CONTINUE TO APCH COAST BETWEEN
   BRO-CRP.  ONCE CENTER GETS TO WITHIN ABOUT 20-30 NM OF
   LANDFALL...LEADING PORTION OF MOST KINEMATICALLY FAVORABLE SECTOR OF
   SYSTEM WILL BEGIN TO SPREAD ONSHORE TO ITS N...INCREASING IN
   COVERAGE WITH TIME AS DON TRANSLATES PROGRESSIVELY FARTHER INLAND. 
   GRADUAL ENLARGEMENT OF LOW-LEVEL HODOGRAPHS IS EVIDENT IN CRP
   ALREADY...AND WILE STILL TOO SMALL TO SUPPORT SUSTAINED SUPERCELL
   STRUCTURES...IS EXPECTED TO RAMP UP PACE OF INCREASE IN 0-1 KM AGL
   SHEAR FROM NOW THROUGH POST-LANDFALL PHASE.
   
   MAIN LIMITING FACTORS WILL BE
   1. SPATIAL...GIVEN SMALL RADII OF FAVORABLE LOW-LEVEL FLOW/SHEAR IN
   THIS SYSTEM.  THIS WILL GREATLY LIMIT LOW-LEVEL VERTICAL SHEAR
   AVAILABLE TO CONVECTION WELL NE OF CENTER--INCLUDING
   OUTFLOW-DOMINANT/MULTICELLULAR ACTIVITY NOW OBSERVED ACROSS
   MID-UPPER TX COASTAL PLAIN.  SHEAR THERE IS NOT EXPECTED TO INCREASE
   GIVEN PATH OF CENTER PASSING ABEAM/AWAY FROM AREA WITH TIME.
   2. MODAL...WITH LACK OF CONVECTIVE COVERAGE IN REGION OF MOST
   FAVORABLE LOW-LEVEL SHEAR NNW THROUGH SE OF CENTER.
   
   AS SUCH...IT IS NOT YET CLEAR THAT THREAT WARRANTS TORNADO WW...BUT
   WILL CONTINUE TO MONITOR CONVECTIVE AND ENVIRONMENTAL WIND TRENDS
   FOR POSSIBLE ISSUANCE LATER TODAY.
   
   REF NHC ADVISORIES FOR LATEST GUIDANCE ON FCST TRACK/INTENSITY OF
   DON.
   
   ..EDWARDS.. 07/29/2011
   
   
   ATTN...WFO...HGX...CRP...EWX...BRO...
   
   LAT...LON   27069735 27159784 27519854 28279865 28919812 29109720
               29049679 28319640 28179668 27919696 27499726 27299734
               27069735