HOME	ACTIVE CYCLONES	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
HURRICANE GERT DISCUSSION NUMBER  12
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT TUE SEP 14 1999
 
INFRARED SATELLITE IMAGERY SHOWS THAT GERT HAS ONCE AGAIN DEVELOPED
AN EYE. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB ARE 90
KT...WHICH WILL BE THE MAXIMUM INTENSITY FOR THIS ADVISORY.

NOW THAT THE EYE HAS RE-FORMED...THE INITIAL MOTION IS LESS
UNCERTAIN AND IS ESTIMATED TO BE 285/13. THE SYNOPTIC PATTERN IS
UNCHANGED FROM 24 HOURS AGO...WITH GERT CONTINUING WEST TO WEST-
NORTHWEST UNDER THE SUBTROPICAL RIDGE. SEVERAL HURRICANE GUIDANCE
MODELS...MOST NOTABLY THE NOGAPS AND THE BAMM...HAVE A TURN TOWARD
THE NORTHWEST DUE TO A WEAKENING RIDGE NEAR THE END OF THE FORECAST
PERIOD. SOME OF THIS WEAKENING APPEARS DUE TO THE INFLUENCE OF
HURRICANE FLOYD IN THE MODELS...WITH ALL THE UNCERTAINTIES THAT
IMPLIES. THUS...THE OFFICIAL FORECAST IS SHIFTED ONLY SLIGHTLY
NORTHWARD FROM THE PREVIOUS PACKAGE. WHILE THE 72 HOUR POINT IS
NORTH OF THE LESSER ANTILLES...GERT COULD STILL BE A THREAT TO THAT
AREA IF THE STORM MOVES MORE TO THE WEST THAN CURRENTLY FORECAST.

THE SHIPS MODEL WANTS TO DEVELOP 20-25 KT VERTICAL WIND SHEAR OVER
GERT BY 36-48 HOURS...AND THUS ONLY INTENSIFIES IT TO 105 KT. A LOOK
AT THE AVN AND NOGAPS 200 MB WIND FIELDS DOES NOT INDICATE THAT
STRONG OF SHEAR OVER THE SYSTEM. THE INTENSITY FORECAST IS THUS A
LITTLE STRONG THAN BOTH SHIPS AND THE PREVIOUS PACKAGE.

THE LONGER RANGE FORECAST OF GERT IS STILL UNCERTAIN. SEVERAL OF THE
GLOBAL MODELS TURN THE HURRICANE NORTHWARD NEAR 60W. HOWEVER...THIS
SEEM TO BE AT LEAST IN PART DUE TO THE INFLUENCE OF FLOYD IN THE
MODELS. THUS...THESE FORECASTS NEED TO BE TAKEN WITH A GRAIN OF SALT
AT THIS TIME.

THE INITIAL AND FORECAST WIND RADII HAVE BEEN ADJUSTED ON THE BASIS
OF A COUPLE OF ERS SATELLITE SCATTEROMETER OVERPASSES.
 
BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     14/0900Z 16.7N  43.9W    90 KTS
12HR VT     14/1800Z 17.2N  46.0W    95 KTS
24HR VT     15/0600Z 17.7N  48.6W   100 KTS
36HR VT     15/1800Z 18.1N  51.5W   105 KTS
48HR VT     16/0600Z 18.5N  54.5W   110 KTS
72HR VT     17/0600Z 19.0N  60.0W   110 KTS
 
 
NNNN