000
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