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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
 
 
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