MESOSCALE DISCUSSION 2064
   NWS STORM PREDICTION CENTER NORMAN OK
   0206 AM CDT SAT AUG 27 2011
   
   AREAS AFFECTED...PORTIONS ERN NC...SERN VA...EXTREME SERN MD.
   
   CONCERNING...TORNADO WATCH 809...810...
   
   VALID 270706Z - 270900Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 809...810...CONTINUES.
   
   PRIND REMAINDER WW 509 CAN BE ALLOWED TO EXPIRE AS SCHEDULED AT 09Z.
    WW 510 CAN BE CLEARED FROM S-N IN STEP WITH MOTION OF IRENE'S CORE
   REGION.  TORNADO THREAT WILL REMAIN GREATEST WITH OUTER-BAND
   SUPERCELLS MOVING ASHORE N-NNE OF CENTER.  AS TC CENTER ITSELF MOVES
   NNE...ALREADY NARROW EXTENT OF FAVORABLE SECTOR OVER LAND WILL
   CONSTRICT EVEN FURTHER COASTWARD ACROSS SERN VA...WHILE POTENTIAL
   DROPS CONSIDERABLY FROM S-N AS CYCLONE CENTER PASSES BY.  GREATEST
   TORNADO PROBABILITIES THROUGH 11Z WILL BE OVER NERN NC...AND HAMPTON
   ROADS REGION ACROSS CAPE CHARLES AREA AND ATLANTIC COAST COUNTIES OF
   VA.
   
   VWP TRENDS AT AKQ INDICATE STRENGTHENING LOW-LEVEL SHEAR/SRH WITH
   TIME...AS EXPECTED WITH APCH OF MIDDLE-OUTER TC ENVELOPE N OF
   CENTER.  SFC MESOANALYSIS SHOWS THERMAL AXIS WITH TEMPS UPPER
   70S-LOW 80S ACROSS CAP CHARLES WWD OVER PTB...AHEAD OF OUTER BANDS. 
   PRECIP AREAS WILL CONTINUE TO CAUSE THETAE DEFICITS TO INCREASE AND
   BUOYANCY TO DECREASE WITH WWD/INLAND EXTENT ACROSS VA/NC AREA...WITH
   RELATIVELY STG COLD POOL EVIDENT FOR A TC ACROSS WRN PORTIONS NC
   COASTAL PLAIN.  THIS REGIME SHOULD SHIFT NNEWD ACROSS S-CENTRAL/SERN
   VA WITH TIME IN STEP WITH TRANSLATIONAL MOTION OF IRENE.  DISTINCT
   SUPERCELLS ARE MOST LIKELY NEAR COAST...AND RADAR TRENDS HAVE
   INDICATE CONSIDERABLE WEAKENING OF MESOCYCLONES ONCE ENTERING ERN
   FRINGES OF COLD-POOL ZONE AND PASSING NNW OF TC CENTER.  MODIFIED
   RAOBS AND MODEL SOUNDINGS SUPPORT THIS IDEA...WITH SFC TEMPS ABOUT
   76 F BECOMING TOO COOL TO YIELD UNINHIBITED MLCAPE BENEATH WARM AIR
   ALOFT THAT CHARACTERIZES MIDDLE-OUTER PORTIONS OF HURRICANE
   ENVELOPE. FARTHER INWARD AND CLOSER TO CENTER...WHERE EVEN WARMER
   AIR ALOFT PREVAILS...CAPE-GENERATING SFC TEMPS ARE JUST SLIGHTLY
   WARMER GIVEN MID-70S F DEW POINTS.  HOWEVER...LACK OF
   DISCRETE/CELLULAR CONVECTIVE STRUCTURE AS EVIDENT IN REFLECTIVITY
   TRENDS...COMBINED WITH LESS-FAVORABLE VERTICAL SHEAR AROUND
   CENTRAL/WRN SWRN SECTORS...INDICATES TORNADO POTENTIAL DROPS
   CONSIDERABLY WITH SWD EXTENT OVER ERN NC.
   
   ..EDWARDS.. 08/27/2011
   
   
   ATTN...WFO...AKQ...MHX...ILM...
   
   LAT...LON   33857855 34007858 35567715 37237679 38427580 38437504
               37997528 37587559 37097589 37047601 36937599 36037564
               35667545 35277550 35117552 35217558 35007604 34727639
               34477651 34637660 34507742 34087782 33657799 33907817
               33857855