000
WTPZ42 KNHC 030240
TCDEP2
 
TROPICAL STORM GIL DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072013
800 PM PDT FRI AUG 02 2013
 
SATELLITE IMAGERY INDICATES THAT GIL HAS SHEARED APART...WITH THE
LOW-LEVEL CENTER BECOMING EXPOSED TO THE WEST OF A DECAYING
MID/UPPER-LEVEL CENTER.  THIS APPEARS TO BE DUE TO 20 KT OF
WEST-SOUTHWESTERLY VERTICAL WIND SHEAR AS ANALYZED BY CIMSS.  AT
THIS TIME...THERE IS LITTLE CONVECTION ASSOCIATED WITH THE
CYCLONE...WHICH MAKES THE SATELLITE INTENSITY ESTIMATES OF 65 KT
FROM TAFB AND 55 KT FROM SAB RATHER UNCERTAIN.  THE INITIAL
INTENSITY IS REDUCED TO 55 KT...AND IT IS POSSIBLE THIS IS
GENEROUS.
 
THE INITIAL MOTION IS 275/10.  GIL IS ON THE SOUTH SIDE OF A
LOW/MID-LEVEL RIDGE...WITH A MID/UPPER-LEVEL TROUGH TO THE NORTH OF
THE STORM.  THE DYNAMICAL MODELS FORECAST THE RIDGE TO STRENGTHEN
SOME DURING THE FORECAST PERIOD AS THE TROUGH MOVES NORTHEASTWARD
AND WEAKENS. THIS EVOLUTION SHOULD STEER GIL GENERALLY WESTWARD
FOR 24-36 HR...FOLLOWED BY A WEST-SOUTHWESTERLY MOTION.  A MORE
WESTWARD TRACK IS EXPECTED BY THE END OF THE PERIOD.  THE TRACK
GUIDANCE IS GENERALLY IN GOOD AGREEMENT WITH THIS SCENARIO.  THE
ONE EXCEPTION IS THE GFS...WITH SHOWS GIL SLOWING AND TURNING
NORTHWESTWARD AFTER 72 HR DUE TO INTERACTION WITH THE DISTURBANCE TO
ITS EAST AND NORTH.  THIS SOLUTION IS DISCOUNTED AT THIS TIME.  THE
NEW FORECAST TRACK IS IN THE MIDDLE OF THE GUIDANCE ENVELOPE AND
LIES A LITTLE SOUTH OF THE PREVIOUS FORECAST AFTER 36 HR.
 
THE INTENSITY FORECAST IS LOW CONFIDENCE.  FIRST...WHILE ALL THE
GUIDANCE FORECASTS WEAKENING DURING THE FIRST 48-72 HR...THE
SHIPS FORECAST SEEMS TO BE BASED ON LESS SHEAR THAN WHAT IS
CURRENTLY OCCURRING.  THUS...THE SHIPS FORECAST OF KEEPING GIL A
TROPICAL STORM FOR 5 DAYS COULD BE OPTIMISTIC.  SECOND...WHILE THE
GLOBAL MODELS AGREE THAT THE CYCLONE WILL ENCOUNTER A MORE
FAVORABLE SHEAR ENVIRONMENT BY 72 HR...NONE OF THEM SHOW MUCH
INTENSIFICATION AS A RESULT.  THIRD...SEVERAL OF THE GLOBAL MODELS
FORECAST THE DISTURBANCE EAST OF GIL DEVELOPING AND BECOMING THE
MORE DOMINANT SYSTEM IN THE AREA.  FINALLY...THERE IS AN INCREASING
POSSIBILITY THAT THIS VERY SMALL CYCLONE MAY NOT SURVIVE TO REACH
THE MORE FAVORABLE ENVIRONMENT.  THE NEW INTENSITY FORECAST CALLS
FOR FASTER WEAKENING THAN THE PREVIOUS FORECAST THROUGH 48 HR...
FOLLOWED BY A SLOWER WEAKENING THAN THE PREVIOUS FORECAST.  THE NEW
FORECAST IS IN BEST AGREEMENT WITH LGEM THROUGH 48 HR...THEN IS IN
BEST AGREEMENT WITH THE HWRF.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0300Z 14.9N 130.6W   55 KT  65 MPH
 12H  03/1200Z 14.9N 131.6W   50 KT  60 MPH
 24H  04/0000Z 14.8N 133.2W   45 KT  50 MPH
 36H  04/1200Z 14.6N 134.6W   40 KT  45 MPH
 48H  05/0000Z 14.3N 136.1W   40 KT  45 MPH
 72H  06/0000Z 13.5N 139.0W   40 KT  45 MPH
 96H  07/0000Z 13.0N 142.0W   35 KT  40 MPH
120H  08/0000Z 13.0N 145.0W   30 KT  35 MPH
 
$$
FORECASTER BEVEN