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SUBTROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 2
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT FRI SEP 20 2002
SATELLITE IMAGERY INDICATES THAT THE NON-TROPICAL LOW THAT IS
CURRENTLY EAST OF BERMUDA IS GETTING BETTER ORGANIZED. THE
CONVECTION IS GETTING CLOSER TO THE CENTER. IN FACT...THERE IS AN
ESTIMATE FOR A 30 KT SUBTROPICAL CYCLONE AND A 35 KT TROPICAL
CYCLONE. THIS SUGGESTS THAT THE SYSTEM IS TRANSFORMING TO A
TROPICAL SYSTEM. THE INITIAL INTENSITY IS INCREASED TO 30 KTS BUT
THE CYCLONE WILL REMAIN SUB-TROPICAL FOR THIS ADVISORY.
SINCE THE HISTORY OF THE SYSTEM IS VERY LIMITED...THE THE INITIAL
MOTION REMAINS SOMEWHAT UNCERTAIN. THE LATEST ESTIMATE IS 360/10.
THE CYCLONE HAS BEEN MOVING NORTHWARD IN RESPONSE TO A SHORT WAVE IN
THE WESTERLIES TO THE NORTH. ALL OF THE GLOBAL MODELS FORECAST THE
SHORT WAVE TO PASS ON TOWARD THE EAST AND LEAVE THE CYCLONE ON THE
SOUTH SIDE OF A BUILDING MID-ATLANTIC OCEAN RIDGE. THE SYSTEM IS
FORECAST TO COME TO A HALT IN 24 TO 36 HOURS AND THEN BE DRIVEN
TOWARD THE SOUTHWEST.
CONDITIONS CURRENTLY APPEAR FAVORABLE FOR DEVELOPMENT...AS THE
CYCLONE SHOWS GOOD OUTFLOW IN A LIGHT SHEAR ENVIRONMENT AND
CONVECTION CONTINUES TO INCREASE NEAR THE CENTER. SEVERAL OF THE
INTENSITY FORECAST MODELS NOW BRING THE SYSTEM TO HURRICANE
INTENSITY IN ABOUT 3 DAYS. THE OFFICIAL FORECAST IS JUST BELOW
HURRICANE FORCE IN 72 HOURS. SHOULD THE SHEAR REMAIN AS LIGHT AS
FORECAST BY THE SHIPS MODEL...THE SYSTEM WOULD HAVE A GOOD CHANCE TO
ACQUIRE FULL TROPICAL CHARACTERISTICS SHORTLY.
THE 12 FOOT SEAS ON THE EAST SIDE OF THE SYSTEM ARE BASED ON A SHIP
OBSERVATION.
FORECASTER JARVINEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 21/0300Z 30.1N 51.2W 30 KTS
12HR VT 21/1200Z 31.4N 51.0W 35 KTS
24HR VT 22/0000Z 32.8N 50.7W 45 KTS
36HR VT 22/1200Z 34.0N 50.5W 50 KTS
48HR VT 23/0000Z 34.0N 51.2W 55 KTS
72HR VT 24/0000Z 32.7N 52.7W 60 KTS
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