SPC Link on NHC
Posted by cypresstx on 8/26/2012, 9:16 am
I'm glad they put that in there - here's the latest mesoscale discussion for south Florida

http://www.spc.noaa.gov/products/md/md1813.html



MESOSCALE DISCUSSION 1813
  NWS STORM PREDICTION CENTER NORMAN OK
  0605 AM CDT SUN AUG 26 2012
 
  AREAS AFFECTED...PORTIONS SRN FL AND KEYS.
 
  CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
 
  VALID 261105Z - 261330Z
 
  PROBABILITY OF WATCH ISSUANCE...95 PERCENT
 
  SUMMARY...TORNADO POTENTIAL WITH ISAAC IS FCST TO INCREASE THROUGH
  REMAINDER MORNING INTO AFTN.  THREAT SHOULD START AS MRGL DURING
  NEXT 1-2 HOURS...BUT INCREASE WITH TIME.  AS SUCH...TORNADO WW MAY
  BE REQUIRED WITHIN NEXT 1-2 HOURS AND IS QUITE LIKELY SOMETIME THIS
  MORNING.  ALSO...IN UPCOMING 13Z DAY-1 OUTLOOK...TORNADO
  PROBABILITIES WILL BE INCREASED FOR S FL...WITHIN BROADER
  CATEGORICAL SLGT RISK.
 
  DISCUSSION...TC TORNADO THREAT IS MRGL ATTM...BUT WILL RAMP UP AND
  EXPAND NWWD ACROSS AREA TODAY AS THESE PROCESSES TAKE PLACE LARGELY
  IN TANDEM...
 
  1. CENTER OF ISAAC PASSES S OF MAINLAND...ACROSS LOWER KEYS INTO
  EXTREME ERN GULF...BASED ON LATEST NHC TRACK FCST.  THIS WILL
  TRANSLATE FAVORABLE NERN SECTOR OF CYCLONE ACROSS DISCUSSION AREA.
  2. STRENGTHENING/EXPANDING LOW-LEVEL WIND FIELDS...PER NHC FCST.
  THAT...IN TURN...WILL RESULT IN INCREASING LOW-LEVEL
  CONVERGENCE...AS WELL AS GREATER MAGNITUDE AND AREAL COVERAGE OF
  ENHANCED LOW-LEVEL VERTICAL SHEAR FAVORABLE FOR TORNADIC SUPERCELLS.
  SHAPE/LENGTH OF FCST HODOGRAPHS CONTRIBUTES TO EFFECTIVE SRH
  INCREASING TO 300-500 J/KG...AND NEARLY 90-DEG CRITICAL ANGLES
  SUGGESTING FAVORABLE STREAMWISE VORTICITY.  THIS WILL ENCOURAGE
  PROGRESSIVELY MORE POTENTIAL FOR SUSTAINED ROTATION IN ANY
  RELATIVELY DISCRETE UPDRAFTS.
  3. RELATIVELY LARGE-THETAE AIR MASS -- NOW EVIDENT OFFSHORE SE FL
  OVER WATERS OF GULF STREAM WHERE OCEAN HEAT CONTENT IS HIGH.  THIS
  AIR MASS SHOULD BE ADVECTED INLAND AMIDST INCREASING BOUNDARY-LAYER
  WINDS TODAY...HELPING TO OFFSET MINOR OUTFLOW EFFECTS OF PASSING
  CONVECTION.  RESULTING MODIFICATIONS TO FCST SOUNDINGS YIELD
  500-1000 J/KG MLCAPE AND LITTLE OR NO SBCINH.
  4. POCKETS OF DIABATIC SFC HEATING MAY BOOST BUOYANCY LOCALLY EVEN
  FURTHER...IN AREAS OF RELATIVE CLOUD-COVER BREAKS.  
  5. MULTIPLE ROUNDS OF AT LEAST LOOSELY BANDED CONVECTIVE MODE ARE
  POSSIBLE AS CONVERGENCE INCREASES.  THIS IS SUGGESTED BY STG
  CONSENSUS OF HIGH-RES/CONVECTION-ALLOWING MODELS...AND SUPPORTS
  INCREASING SUPERCELL/TORNADO CHANCES.
 
  ..EDWARDS/THOMPSON.. 08/26/2012
 
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SPC Link on NHC - cypresstx, 8/26/2012, 9:16 am
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