000
WTPZ42 KNHC 311445
TCDEP2
 
TROPICAL STORM GIL DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072013
800 AM PDT WED JUL 31 2013

SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN IS A LITTLE BETTER
ORGANIZED...WITH A DISTINCT AREA OF CONVECTION NEAR THE CENTER AND A
FEW HOOKING BANDS.  MICROWAVE DATA SUGGEST THAT THE CENTER IS
EMBEDDED WITHIN OR VERY NEAR THE MAIN AREA OF DEEP CONVECTION. A
BLEND OF SUBJECTIVE AND OBJECTIVE SATELLITE INTENSITY ESTIMATES
YIELDS AN INITIAL INTENSITY OF 50 KNOTS. GIVEN THAT THE SHEAR IS
FORECAST TO BE LIGHT FOR THE NEXT FEW DAYS AND THE OCEAN IS
WARM...THE OFFICIAL FORECAST CALLS FOR GIL TO BECOME A HURRICANE IN
A DAY OR SO. THE GLOBAL MODELS...PRIMARILY THE GFS...FORECAST AN
INCREASE IN THE UPPER-LEVEL WESTERLIES OVER OR NEAR THE CYCLONE
DURING THE LATTER PART OF THE FORECAST PERIOD. THIS PATTERN...IN
COMBINATION WITH COOLER WATERS...SHOULD RESULT IN GRADUAL
WEAKENING.      

THE INITIAL MOTION HAS NOT CHANGED SIGNIFICANTLY AND THE BEST
ESTIMATE IS 285/12. GIL IS CURRENTLY BEING STEERED BY THE FLOW
SOUTH OF A SUBTROPICAL RIDGE WHICH IS FORECAST TO PERSIST. BOTH THE
GFS AND THE ECMWF MODELS DEVELOP A WEAKNESS IN THE MID-LEVEL RIDGE
NORTH OF THE CYCLONE IN ABOUT 3 DAYS. THIS WOULD OFTEN IMPLY A MORE
NORTHWESTERLY TRACK. HOWEVER...THESE MODELS SUGGEST THAT THE CYCLONE
WILL BECOME VERTICALLY DECOUPLED AND A WEAKENED LOWER-LEVEL
CYCLONE WILL CONTINUE WESTWARD...STEERED BY THE LOW-LEVEL FLOW...
WHILE THE MID-LEVEL CIRCULATION MOVES NORTHWARD. THE OFFICIAL
FORECAST KEEPS GIL ON A GENERAL WESTWARD TRACK...WHICH IS IN FACT
VERY CLOSE TO THE MULTI-MODEL CONSENSUS AND THE WESTWARD MOTION OF
THE LOW-LEVEL VORTEX IMPLIED BY THE GFS AND THE ECMWF.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/1500Z 13.6N 119.9W   50 KT  60 MPH
 12H  01/0000Z 14.1N 121.6W   55 KT  65 MPH
 24H  01/1200Z 14.6N 124.0W   60 KT  70 MPH
 36H  02/0000Z 15.0N 125.7W   65 KT  75 MPH
 48H  02/1200Z 15.3N 127.6W   65 KT  75 MPH
 72H  03/1200Z 15.8N 131.0W   60 KT  70 MPH
 96H  04/1200Z 16.0N 134.5W   50 KT  60 MPH
120H  05/1200Z 16.0N 138.0W   35 KT  40 MPH
 
$$
FORECASTER AVILA