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TROPICAL STORM GABRIELLE DISCUSSION NUMBER  29
NATIONAL WEATHER SERVICE MIAMI FL
5 PM EDT TUE SEP 18 2001
 
DEEP CONVECTION HAS PERSISTED NORTH AND WEST OF THE LOW-LEVEL 
CIRCULATION CENTER. HOWEVER...THE APPEARANCE OF THIS SYSTEM IS MORE 
INDICATIVE OF AN EXTRATROPICAL LOW. THE INITIAL INTENSITY IS 
INCREASED TO 60 KTS BASED PRIMARILY ON AN OBSERVATION FROM SHIP WMLH 
LOCATED ABOUT 90 NM NW OF THE CENTER. THE SHIP REPORTED 984.5 MB 
PRESSURE...75F AIR TEMPERATURE...72F DEWPOINT. THIS DATA COUPLED 
WITH AMSU DATA STILL INDICATES THAT GABRIELLE REMAINS A WARM CORE 
SYSTEM...WHICH JUSTIFIES MAINTAINING IT AS A TROPICAL STORM FOR THIS 
ADVISORY.
 
INITIAL MOTION ESTIMATE IS 045/16. THERE REMAINS LITTLE CHANGE IN 
THE PREVIOUS FORECAST TRACK OR REASONING. GABRIELLE IS EXPECTED TO 
ACCELERATE NORTHEASTWARD THROUGH THE FORECAST PERIOD AS STRONG 
WESTERLY MID-LATITUDE FLOW BEGINS TO AFFECT THE SYSTEM IN 12-24 
HOURS. THIS SCENARIO IS SUPPORTED BY ALL OF THE GLOBAL MODELS... 
WHICH REMAIN IN EXCELLENT AGREEMENT ON KEEPING THE CENTER OF 
GABRIELLE OFF THE NEWFOUNDLAND COAST THROUGH 48 HOURS.
 
THE GLOBAL MODELS ARE INDICATING SOME ADDITIONAL INTENSIFICATION 
WITH THIS SYSTEM IN 12 TO 24 HOURS AS IT TRANSITIONS TO AN   
EXTRATROPICAL LOW. IN FACT THE INTENSITY FORECAST IS INCREASED FROM 
THE EARLIER ADVISORY...ACCOUNTING FOR THE GLOBAL MODELS TREND IN 
DEVELOPING A STRONGER SYSTEM. HOWEVER...GABRIELLE SHOULD QUICKLY 
BECOME EXTRATROPICAL ONCE THE SYSTEM PASSES NORTH OF 43N LATITUDE 
WHERE WATER TEMPERATURES DROP BELOW 20C.
 
FORECASTER STEWART/HOLWEG
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     18/2100Z 40.6N  58.4W    60 KTS...BECOMING EXTRATROPICAL
12HR VT     19/0600Z 42.4N  55.9W    60 KTS...EXTRATROPICAL
24HR VT     19/1800Z 44.9N  52.1W    60 KTS...EXTRATROPICAL
36HR VT     20/0600Z 47.3N  47.7W    60 KTS...EXTRATROPICAL
48HR VT     20/1800Z 49.3N  42.2W    60 KTS...EXTRATROPICAL
72HR VT     21/1800Z 51.0N  33.5W    55 KTS...EXTRATROPICAL
 
 
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