Tropical Storm GIL

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TROPICAL STORM GIL DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072013
200 PM PDT SAT AUG 03 2013
 
DEEP CONVECTION HAS CONTINUED TO BURST INTERMITTENTLY NEAR THE
CENTER OF GIL DURING THE PAST SEVERAL HOURS.  DVORAK CI ESTIMATES
RANGE FROM 35 TO 65 KT...A DISCREPANCY THAT CAN BE EXPLAINED IN
PART BY THE PULSATING NATURE OF THE CONVECTION.  THE INTENSITY HAS
BEEN HELD AT 50 KT AS A CONSERVATIVE COMPROMISE BETWEEN THESE
ESTIMATES...HOWEVER BASED ON LONG-TERM TRENDS...THIS MAY BE
GENEROUS.  THE INTENSITY GUIDANCE HAS NOT COME INTO BETTER
AGREEMENT.  THE STATISTICAL MODELS FORECAST THAT THE INTENSITY WILL
NOT CHANGE MUCH DURING THE NEXT COUPLE OF DAYS...AND THAT
STRENGTHENING WILL OCCUR AFTER THAT.  THE UW-CIMSS SHEAR ANALYSIS
SUGGESTS THAT THE SHEAR IS SUBSTANTIALLY HIGHER THAN THE SHIPS
ANALYSIS INDICATES...WHICH MAY EXPLAIN WHY THE STATISTICAL MODELS
FORECAST INTENSIFICATION.  THE OFFICIAL FORECAST HAS NOT BEEN
CHANGED SUBSTANTIALLY...AND LEANS TOWARD THE DYNAMICAL MODEL
CONSENSUS FORECAST OF GRADUAL WEAKENING.

GIL CONTINUES TO MOVE ON A STEADY WESTWARD HEADING AT 11 KT...
STEERED BY A MID-LEVEL RIDGE LOCATED TO THE NORTHEAST.  THE GLOBAL
MODELS AGREE THAT THIS RIDGE WILL BUILD TOWARD THE SOUTHWEST OVER
THE NEXT 48 TO 72 HOURS...WHICH SHOULD CAUSE THE CYCLONE TO TURN
TOWARD THE WEST-SOUTHWEST.  AFTER THAT TIME...THERE IS ONCE AGAIN A
LARGE AMOUNT OF SPREAD IN THE TRACK GUIDANCE.  IN FACT...THE GFS
AND ECMWF MODEL DAY 5 FORECAST POSITIONS ARE NEARLY 600 MILES
APART.  THE PRIMARY DIFFERENCE BETWEEN THESE MODELS SEEMS TO BE THE
DEPTH OF THE CIRCULATION. THE ECMWF FORECASTS A MUCH SHALLOWER
SYSTEM THAT IS STEERED PRIMARILY BY LOW-LEVEL EASTERLIES...WHILE
THE GFS FORECASTS A DEEPER CYCLONE THAT SLOWS AND TURNS TOWARD THE
NORTH.  THE OFFICIAL FORECAST IS A BLEND OF THESE TWO SOLUTIONS...
AND CALLS FOR WESTWARD MOTION AFTER DAY 3...IN LINE WITH THE
INTENSITY FORECAST FOR A WEAKER CYCLONE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/2100Z 15.3N 133.6W   50 KT  60 MPH
 12H  04/0600Z 15.3N 134.9W   45 KT  50 MPH
 24H  04/1800Z 14.8N 136.3W   45 KT  50 MPH
 36H  05/0600Z 14.4N 137.6W   45 KT  50 MPH
 48H  05/1800Z 13.9N 139.2W   40 KT  45 MPH
 72H  06/1800Z 13.0N 142.0W   40 KT  45 MPH
 96H  07/1800Z 13.0N 145.0W   35 KT  40 MPH
120H  08/1800Z 13.0N 148.0W   30 KT  35 MPH
 
$$
FORECASTER FRANKLIN/ZELINSKY
 
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