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TROPICAL STORM BONNIE DISCUSSION NUMBER   5
NATIONAL WEATHER SERVICE MIAMI FL
4 PM EST THU AUG 20 1998
 
THE HURRICANE HUNTERS FOUND FLIGHT-LEVEL WINDS TO 61 KNOTS TO THE
NORTH OF A RATHER ILL-DEFINED LOW-LEVEL CENTER.  THIS WARRANTS
UPGRADING T.D. TWO TO TROPICAL STORM BONNIE. ALTHOUGH THE STORM HAS
A WELL-ORGANIZED APPEARANCE IN SATELLITE IMAGERY...ITS RAPID FORWARD
TRANSLATIONAL SPEED IS APPARENTLY DISTORTING THE WIND FIELD NEAR THE
CENTER.  THE ATMOSPHERIC ENVIRONMENT REMAINS FAVORABLE FOR CONTINUED
STRENGTHENING AND INTENSIFICATION IS EVEN MORE LIKELY IF THE FORWARD
SPEED SLOWS SOMEWHAT...AS FORECAST.
 
BONNIE HAS BEEN TRACKING SLIGHTLY NORTH OF DUE WEST TODAY...BUT
PRACTICALLY ALL OF THE TRACK PREDICTION MODELS EXCEPT THE GFDL SHOW
A SIGNIFICANT TURN TO THE RIGHT.  THIS IS CONSISTENT WITH A
BREAKDOWN OF THE MID-TROPOSPHERIC RIDGE OVER THE WESTERN ATLANTIC AS
SHOWN BY THE GLOBAL MODELS.  NOTWITHSTANDING...OUT OF RESPECT FOR
WHAT WE CONSIDER TO BE OUR MOST RELIABLE GUIDANCE...THE GFDL...WE
ARE KEEPING THE OFFICIAL FORECAST TRACK ON THE SOUTHERN SIDE OF THE
ENSEMBLE.
 
SINCE THE FORECAST TRACK IS RATHER CLOSE TO THE VIRGIN ISLANDS AND
PUERTO RICO...TROPICAL STORM WARNINGS AND WATCHES HAVE BEEN ISSUED
FOR THESE AREAS.  HOWEVER AT THIS TIME IT APPEARS THAT THE STRONG
WINDS ARE RESTRICTED MAINLY TO THE NORTHERN SEMICIRCLE OF BONNIE.
 
THE STEERING ENVIRONMENT IS BEING SAMPLED BY A MAJOR SYNOPTIC FLOW
EXPERIMENT INVOLVING BOTH THE NOAA P-3S AND G-4 AIRCRAFT.  FIFTY-
NINE GLOBAL POSITIONING SONDES WILL BE DEPLOYED FROM THESE PLATFORMS
FOR THE 00Z INITIALIZATION OF THE LARGE-SCALE MODELS.

PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     20/2100Z 17.9N  60.7W    45 KTS
12HR VT     21/0600Z 19.1N  63.7W    50 KTS
24HR VT     21/1800Z 20.5N  67.0W    55 KTS
36HR VT     22/0600Z 22.0N  70.0W    55 KTS
48HR VT     22/1800Z 23.5N  72.5W    65 KTS
72HR VT     23/1800Z 26.5N  75.0W    75 KTS
 
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