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HURRICANE GIL DISCUSSION NUMBER  10
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT THU SEP 06 2001
 
GIL CONTINUES TO GET BETTER ORGANIZED...WITH A SOLID 20 NM DIAMETER 
CLOSED EYE INDICATED IN A 06/0214 SSMI OVERPASS. DVORAK SATELLITE 
INTENSITY ESTIMATES ARE 77 KT...T4.5...FROM BOTH TAFB AND SAB...AND 
65 KT...T4.0...FROM AFWA.  THEREFORE... THE INITIAL INTENSITY HAS 
BEEN INCREASED TO 75 KT.  THE UPPER-LEVEL OUTFLOW REMAINS GOOD IN 
ALL QUADRANTS DESPITE THE SLIGHT EASTERLY UPPER-LEVEL SHEAR BEING 
CREATED BY THE OUTFLOW FROM TROPICAL STORM HENRIETTE...WHICH IS 
LOCATED ABOUT 480 NMI TO THE EAST-NORTHEAST OF GIL.
 
THE INITIAL MOTION ESTIMATE IS 280/5.  SIMILAR TO TROPICAL STORM 
HENRIETTE DISCUSSION...THERE IS LIKELY SOME BINARY INTERACTION 
OCCURRING BETWEEN THE TWO CYCLONES.  HOWEVER...THE DOMINANT STEERING 
FLOW SHOULD CONTINUE TO COME FROM THE DEEP SUBTROPICAL RIDGE 
SITUATED TO THE NORTH OF BOTH HENRIETTE AND GIL.  SURFACE ANALYSES 
INDICATE THAT GIL AND HENRIETTE ARE EMBEDDED WITHIN A LARGER-SCALE 
GYRE THAT SHOULD SHIFT WESTWARD DUE TO THE DEEP EASTERLY FLOW ON THE 
SOUTHERN SIDE OF THE LARGE EAST-WEST ORIENTED SUBTROPICAL RIDGE.  
THE GLOBAL MODELS ARE HAVING A DIFFICULT TIME KEEPING THE TWO 
TROPICAL CYCLONES AS SEPARATE ENTITIES FOR MORE THAN ABOUT 36 
HOURS...ALTHOUGH THEY KEEP GIL AS THE DOMINANT CIRCULATION. THE 
FORECAST TRACK FOR GIL IS BASED IN PART ON HOW LONG HENRIETTE 
SURVIVES.  THE INCREASED OUTFLOW ON THE WEST SIDE OF HENRIETTE THIS 
MORNING HAS HELPED TO NUDGE GIL A LITTLE FASTER TO THE WEST.  THIS 
"PUSH-PULL" PATTERN BETWEEN THE TWO SYSTEMS WILL LIKELY CONTINUE FOR 
AT LEAST 48 HOURS...AFTER WHICH HENRIETTE WILL BEGIN TO WEAKEN... 
WHICH MAY CAUSE GIL TO SLOW DOWN AGAIN.  THE OFFICAL FORECAST IS A 
LITTLE NORTH OR TO THE RIGHT OF THE PREVIOUS TRACK AND IS BETWEEN 
THE NOGAPS AND MEDIUM BAM MODELS.

GIL SHOULD CONTINUE TO STRENGTHEN SINCE IT HAS A TIGHTER CONVECTIVE 
PATTERN AND LOW-LEVEL CIRCULATION... AS INDICATED IN AN EARLIER 
QUIKSCAT OVERPASS...THAN HENRIETTE DOES.  HOWEVER...THE UNCERTAINTY 
IN WHAT EFFECT THE SHEARING OUTFLOW FROM HENRIETTE WILL HAVE ON GIL 
REQUIRES THAT THE INTENSITY FORECAST REMAIN RATHER CONSERVATIVE. THE 
SHIPS INTENSITY FORECAST MODEL WAS FOLLOWED CLOSELY...WHICH BRINGS 
GIL UP TO 83 KT IN 12 TO 24 HOURS.  NOTE THAT ONLY A SLIGHT DECREASE 
IN THE EASTERLY SHEAR COULD ALLOW GIL TO REACH 90 TO 95 KT IN THE 
NEXT 24 HOURS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     06/0900Z 15.3N 126.8W    75 KTS
12HR VT     06/1800Z 15.5N 127.8W    80 KTS
24HR VT     07/0600Z 15.9N 129.2W    85 KTS
36HR VT     07/1800Z 16.4N 130.6W    85 KTS
48HR VT     08/0600Z 17.0N 132.0W    75 KTS
72HR VT     09/0600Z 18.0N 134.5W    65 KTS
 
 
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