HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

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HURRICANE GERT DISCUSSION NUMBER  23
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT THU SEP 16 1999
 
THERE HAVE BEEN NO RECONNAISSANCE DATA SINCE ABOUT 20Z.  AT THAT
TIME PEAK FLIGHT LEVEL WINDS WERE 127 KT...THIS SUPPORTS A SURFACE
WIND OF 115 KT.  DROPSONDES IN THE NORTHEAST AND NORTHWEST QUADRANTS
OF THE EYEWALL REPORTED SURFACE WINDS OF ABOUT 85 AND 110 KT
RESPECTIVELY.  SATELLITE CLASSIFICATIONS FROM TAFB AND SAB ARE 127
AND 115 KT.  THE OFFICIAL INTENSITY IS HELD AT 115 KT FOR THIS
PACKAGE...AND ANOTHER AIRCRAFT WILL BE IN THE CYCLONE AT 06Z.  THERE
IS NO SHIPS INTENSITY MODEL RUN FOR THIS CYCLE...BUT THE SPREAD OF
THE BAM MODELS SUGGESTS LOW SHEAR OVER THE NEXT THREE DAYS.  WATER
TEMPERATURES REMAIN WARM SO THE CURRENT INTENSITY IS MAINTAINED
THROUGHOUT THE FORECAST PERIOD...ALTHOUGH FLUCTUATIONS IN INTENSITY
ASSOCIATED WITH INNER CORE/EYEWALL DYNAMICS ARE TO BE EXPECTED. 
WIND RADII HAVE BEEN SUBSTANTIALLY ADJUSTED BASED ON THE LATEST
RECON DATA.

THE INTIAL MOTION REMAINS 300/9.  THERE HAS BEEN A NOTICEABLE SHIFT
IN THE GUIDANCE...WITH ALL MODELS DEPENDENT ON THE AVN SHOWING A
LEFTWARD TURN AT THE END OF THE PERIOD.  ONCE AGAIN...THE AVN IS
HAVING SEVERE PROBLEMS INITIALIZING THE VORTEX...AND THIS APPEARS TO
LEAD TO THE DEVELOPMENT OF A MID-LEVEL TROUGH TO THE SOUTHWEST OF
THE CYCLONE.  THE NOGAPS AND THE UKMET TRACKS DO NOT HAVE THE LEFT
TURN.  THERE ARE TWO GFDL RUNS...ONE RUN OFF THE NOGAPS...GFNI...AND
ONE OFF THE AVN...GFDI.  ONLY THE GFDI SHOWS THE TURN.  I AM NOT
READY TO BITE ON THIS GUIDANCE AND MAINTAIN A SLOWLY RECURVING TRACK
THAT IS HALFWAY BETWEEN THE UKMET AND GFNI.  ON THIS TRACK BERMUDA
IS A POTENTIAL TARGET IN ABOUT 4 DAYS.

THE MAXIMUM WINDS IN THE PUBLIC ADVISORY ARE SET TO 135 MPH FOR
CONSISTENCY IN THE SAFFIR-SIMPSON SCALE.

FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     17/0300Z 19.4N  54.6W   115 KTS
12HR VT     17/1200Z 20.1N  55.8W   115 KTS
24HR VT     18/0000Z 21.5N  57.4W   115 KTS
36HR VT     18/1200Z 22.8N  58.7W   115 KTS
48HR VT     19/0000Z 24.5N  60.0W   115 KTS
72HR VT     20/0000Z 28.0N  62.0W   115 KTS
 
 
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