709 
 WTNT44 KNHC 131450
 TCDAT4
  
 TROPICAL STORM HUMBERTO DISCUSSION NUMBER  20
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092013
 1100 AM AST FRI SEP 13 2013
 
 VERTICAL SHEAR IS TAKING ITS TOLL ON HUMBERTO.  ALL OF THE DEEP
 CONVECTION HAS BEEN SHEARED AWAY FROM THE CIRCULATION...LEAVING AN 
 EXPOSED CENTER WITH SOME IMPRESSIVE MESOVORTICES.  THE INITIAL WIND
 SPEED IS LOWERED TO 55 KT...BASICALLY AS FAST AS THE DVORAK
 CONSTRAINTS ALLOW.  FURTHER WEAKENING SEEMS PROBABLE FOR THE NEXT
 DAY OR SO DUE TO INCREASING SOUTHWESTERLY SHEAR AND MARGINAL SSTS. 
 IN A COUPLE OF DAYS...THE VERTICAL WIND SHEAR SHOULD BEGIN TO
 DIMINISH WHILE HUMBERTO MOVES OVER WARMER WATERS...WHICH COULD
 ALLOW FOR SOME RESTRENGTHENING.  GLOBAL MODELS SUGGEST THAT THE
 STORM WILL UNDERGO A TROUGH INTERACTION IN THE LONG RANGE...LEAVING
 IT IN A FAVORABLE ENVIRONMENT TO BECOME EVEN STRONGER.  THE
 OFFICIAL INTENSITY FORECAST IS LOWERED FROM THE PREVIOUS ONE DURING
 THE FIRST 36 HOURS BASED ON CURRENT TRENDS AND THE RATHER STRONG
 SHEAR FORECAST.  AT THE END OF THE PERIOD...THE NHC FORECAST IS A
 LITTLE HIGHER...BUT IS STILL BELOW THE MODEL CONSENSUS.  
 
 THE INITIAL MOTION IS 300/9.  A WEST-NORTHWEST TRACK OF HUMBERTO IS
 EXPECTED FOR THE NEXT COUPLE OF DAYS DUE TO A STRONG RIDGE OVER THE
 NORTHEASTERN ATLANTIC.  THE STORM SHOULD TURN NORTHWARD BY DAYS 4-5
 WHILE IT RECURVES AROUND THE WESTERN SIDE OF THE RIDGE.  THE ONLY
 SIGNIFICANT DIFFERENCE IN THE MODEL GUIDANCE IS HOW FAST THE STORM
 ACCELERATES INTO THE FAR NORTH ATLANTIC OCEAN...WHICH DEPENDS ON
 WHAT PARTICULAR SHORTWAVE AMPLIFIES THE NEXT MID-LATITUDE TROUGH. 
 THE NEW NHC PREDICTION WILL STAY CLOSE TO THE PREVIOUS ONE...NEAR
 THE FLORIDA STATE SUPERENSEMBLE AND A BIT FASTER THAN THE DYNAMICAL
 MODEL CONSENSUS.
 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  13/1500Z 24.7N  31.3W   55 KT  65 MPH
  12H  14/0000Z 25.4N  32.7W   45 KT  50 MPH
  24H  14/1200Z 26.3N  35.0W   40 KT  45 MPH
  36H  15/0000Z 27.4N  37.3W   40 KT  45 MPH
  48H  15/1200Z 28.5N  39.4W   40 KT  45 MPH
  72H  16/1200Z 30.7N  42.5W   45 KT  50 MPH
  96H  17/1200Z 32.8N  45.0W   55 KT  65 MPH
 120H  18/1200Z 36.5N  44.5W   65 KT  75 MPH
  
 $$
 FORECASTER BLAKE