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HURRICANE GERT DISCUSSION NUMBER  10
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT MON SEP 13 1999
 
SATELLITE LOOPS DURING THE DAY INDICATE THAT GERT CONTINUES TO
BECOME BETTER ORGANIZED AND IN FACT AN EYE FEATURE APPARENT ON
VISIBLE IMAGES. T-NUMBERS FROM SAB AND TAFB ARE 4.5 ON THE DVORAK
SCALE.THEREFORE..THE WINDS HAVE BEEN INCREASED TO 75 KNOTS.
 
SHIPS...BRINGS GERT TO 104 KNOTS WHILE THE GFDL CONTINUES TO LOWER
THE PRESSURE TO NEAR 940 MB BY 72 HOURS. THESE MODELS HAVE BEEN
PERFORMING VERY WELL IN FORECASTING INTENSITY TRENDS SO FAR THIS
YEAR.  THEREFORE...THE OFFICIAL FORECAST BRINGS GERT TO 105 KNOTS IN
3 DAYS.
 
GERT IS NOW MOVING 270/16.  THERE IS A STRONG SUBTROPICAL RIDGE TO
THE NORTH OF THE HURRICANE WHICH IS FORECAST TO PERSIST AND EVEN
STRENGTHEN. THEREFORE A CONTINUED WESTWARD TRACK IS EXPECTED THROUGH
72 HOURS. THIS IS CONSISTENT WITH TRACK MODELS..INCLUDING THE GFDL
WHICH MOVES GERT SOUTH OF DUE WEST FOR A PERIOD OF 24 TO 36 HOURS.
LONGER RANGE MODELS PUT THE HURRICANE VERY NEAR OR OVER THE NORTHERN
LEEWARD ISLANDS IN ABOUT 4 DAYS.  HOWEVER...THESE FORECASTS ARE
HIGHLY UNCERTAIN.
 
AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     13/2100Z 16.0N  41.6W    75 KTS
12HR VT     14/0600Z 16.0N  44.0W    85 KTS
24HR VT     14/1800Z 16.0N  47.5W    90 KTS
36HR VT     15/0600Z 16.3N  50.5W    95 KTS
48HR VT     15/1800Z 16.5N  53.0W   100 KTS
72HR VT     16/1800Z 17.5N  58.0W   105 KTS
 
 
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