Tropical Storm COLIN

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TROPICAL STORM COLIN DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 PM AST SAT AUG 07 2010
 
THE CENTER OF COLIN IS VERY DIFFICULT TO LOCATE THIS EVENING...EVEN
WITH THE HELP OF A TRMM MICROWAVE OVERPASS.  THE BEST ESTIMATE IS
THAT IT IS NORTH OF THE CURRENTLY SHRINKING AREA OF CONVECTION. 
SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND 30 KT FROM
SAB.  BASED ON THIS...THE SYSTEM REMAINS A 35 KT TROPICAL
STORM...AND THIS COULD BE GENEROUS.  COLIN IS STRUGGLING TO
MAINTAIN ITSELF IN A SEEMINGLY FAVORABLE LOW-SHEAR ENVIRONMENT...
AND ONE POSSIBLE REASON IS A TONGUE OF LOW PRECIPITABLE WATER AIR
SEEN INTRUDING INTO THE CIRCULATION IN AN AMSR-E OVERPASS.
 
THE INITIAL MOTION IS A HIGHLY UNCERTAIN 015/3.  IN THE SHORT
TERM...COLIN APPEARS TO BE TRAPPED BETWEEN LOW-LEVEL RIDGES TO THE
EAST AND WEST...AND THIS COULD BE A REASON FOR THE CURRENT SLOW
MOTION.  IN THE LONGER TERM...A DEEP-LAYER TROUGH AND ASSOCIATED
FRONTAL SYSTEM MOVING OFF THE EAST COAST OF THE UNITED STATES
SHOULD STEER THE STORM NORTHWARD AND THEN NORTHEASTWARD INTO THE
WESTERLIES.  THE TRACK GUIDANCE REMAINS IN GOOD AGREEMENT WITH
THIS...AND THE NEW TRACK FORECAST IS SIMILAR TO...BUT SLOWER
THAN...THE PREVIOUS FORECAST.  IT SHOULD BE NOTED THAT SEVERAL OF
THE DYNAMICAL MODELS NOW FORECAST COLIN TO TAKE 24 OR MORE HOURS
BEFORE PASSING BERMUDA.
 
THE INTENSITY GUIDANCE AGREES THAT COLIN SHOULD STRENGTHEN DURING
THE NEXT 36 HR.  GIVEN THE CURRENT INTENSITY TREND AND LACK OF
ORGANIZATION...IT IS LIKELY THAT ANY STRENGTHENING WILL BE SLOWER
THAN THE GUIDANCE.  THE NEW INTENSITY FORECAST IS THE SAME AS THE
PREVIOUS FORECAST...WITH COLIN SLOWLY STRENGTHENING TO 45 KT IN 48
HR.  AN ALTERNATIVE SCENARIO IS THAT COLIN DOES NOT STRENGTHEN AND
REMAINS AT BEST A MINIMAL TROPICAL STORM AS IT MOVES NORTHWARD. 
REGARDLESS OF THE EXACT INTENSITY...COLIN SHOULD BEGIN
EXTRATROPICAL TRANSITION AT AROUND 48 HR AND COMPLETE IT BY 72 HR. 
THE CYCLONE IS THEN LIKELY TO BE ABSORBED BY A LARGER EXTRATROPICAL
LOW BY 96 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 29.7N  65.6W    35 KT
 12HR VT     08/1200Z 30.7N  65.5W    35 KT
 24HR VT     09/0000Z 32.4N  65.5W    40 KT
 36HR VT     09/1200Z 34.7N  64.9W    45 KT
 48HR VT     10/0000Z 38.1N  62.6W    45 KT
 72HR VT     11/0000Z 47.5N  51.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     12/0000Z...ABSORBED BY EXTRATROPICAL LOW
 
$$
FORECASTER BEVEN
 
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