ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM SUBTROPICAL STORM TWO DISCUSSION NUMBER 3 NATIONAL WEATHER SERVICE MIAMI FL 4 AM EST SUN NOV 25 2001 SUBTROPICAL STORM TWO IS BEGINNING TO LOOK MORE TROPICAL AND LESS EXTRATROPICAL IN SATELLITE IMAGERY. THE INNER-CORE CONVECTION NEAR THE LOW-LEVEL CENTER HAS BECOME DETACHED FROM THE MAIN CLOUD SHIELD DURING THE PAST FEW HOURS. IN ADDITION...TWO INTERLOCKING BANDS OF CONVECTION HAVE BECOME MORE DISTINCT AROUND THE CENTER. OUTFLOW IS FAIR TO THE NORTH AND WEAK TO THE SOUTH. THE INITIAL INTENSITY OF 50 KT IS BASED ON A BLEND OF DVORAK SATELLITE INTENSITY ESTIMATES OF 50 KT...45 KT...AND 55 KT FROM TAFB...SAB...AND AFWA...RESPECTIVELY. THE INITIAL MOTION ESTIMATE IS 295/14. SUBTROPICAL STORM TWO HAS ACCELERATED MORE WESTWARD DURING THE PAST 6 HOURS IN RESPONSE TO THE LARGE SURFACE HIGH AND MID-LEVEL RIDGE THAT HAVE STARTED BUILDING EASTWARD TO THE NORTH OF THE CYCLONE. WATER VAPOR IMAGERY INDICATES THE POWERFUL MID-LATITUDE LOW OVER THE U.S. GREAT LAKES REGION LIFTING OUT TO THE NORTHEAST...WHICH IS ACTING TO THE AMPLIFY THE DOWNSTREAM RIDGING OFF THE U.S. EAST COAST. THIS BLOCKING PATTERN IS EXPECTED TO PERSIST THROUGHOUT THE FORECAST PERIOD...WHICH SHOULD ACT TO KEEP THE STORM MOVING IN A GENERAL WESTWARD DIRECTION. ALMOST ALL OF THE NHC MODEL GUIDANCE AGREE ON A WEST-NORTHWEST OR WESTWARD TRACK...WITH A SIGNIFICANT DECREASE IN FORWARD SPEED BY 36 TO 48 HOURS. IT IS POSSIBLE THAT THE CYCLONE COULD EVEN STALL DURING THAT TIME PERIOD AND MOVE ERRATICALLY. HOWEVER...ALL OF THE AVAILABLE GUIDANCE AGREE ON KEEPING THE STORM SYSTEM WELL TO THE EAST OF BERMUDA THROUGH 72 HOURS. THE OFFICIAL FORECAST IS SLIGHTLY SOUTH OR TO THE LEFT OF THE PREVIOUS FORECAST TRACK AND IS CLOSE TO THE AVN-GFDL-UKMET MODEL CONSENSUS. BASED ON THE IMPROVING SATELLITE SIGNATURE...IT IS ENTIRELY POSSIBLE THAT SUBTROPICAL STORM TWO COULD TRANSITION OVER COMPLETELY TO A TROPICAL CYCLONE LATER TODAY. ALL OF THE GLOBAL MODELS AGREE THAT THE UPPER-LEVEL SHEAR WILL WEAKEN THROUGHOUT THE FORECAST PERIOD. IN FACT...BY 48 HOURS...THE AVN MODEL DECREASES THE SHEAR TO LESS THAN 10 KT. AS SUCH...SLOW STRENGTHENING IS FORECAST THROUGH 36 HOURS...EVEN THOUGH SEA-SURFACE TEMPERATURES ARE COOLER THAN 24C. HOWEVER...THE UNSUALLY COLD MID- AND UPPER-LEVEL ENVIRONMENT IS PROVIDING THE NECESSARY INSTABILITY FOR THUNDERSTORM DEVELOPMENT TO OCCUR. THE NEW FORECAST TRACK ACTUALLY TAKES THE CYCLONE OVER WARMER SSTS...SO SOME STRENGTHENING APPEARS TO BE IN ORDER. GIVEN THE FAVORABLE UPPER-LEVEL WINDS FORECAST...THIS SYSTEM COULD EVEN REACH HURRICANE INTENSITY. THE WIND RADII WERE DECREASED AFTER 36 HOURS TO REFLECT THE EXPECTED SHRINKING OF THE OUTER WIND FIELD OWING TO THE WEAKENING SURFACE HIGH TO THE NORTH...AND CONTRACTION OF THE INNER-CORE WIND FIELD WHEN THE SYSTEM BECOMES MORE TROPICAL-LIKE. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 25/0900Z 32.0N 52.3W 50 KTS 12HR VT 25/1800Z 32.3N 53.5W 55 KTS 24HR VT 26/0600Z 32.5N 54.7W 55 KTS 36HR VT 26/1800Z 32.5N 55.7W 60 KTS 48HR VT 27/0600Z 32.4N 56.7W 60 KTS 72HR VT 28/0600Z 32.2N 58.0W 60 KTS NNNN