Tropical Storm COLIN

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TROPICAL STORM COLIN DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 AM EDT TUE AUG 03 2010
 
THE TROPICAL CYCLONE HAS BECOME BETTER ORGANIZED OVER THE PAST
SEVERAL HOURS.  ENHANCED INFRARED SATELLITE IMAGES SHOW A CURVED
BAND WRAPPING HALFWAY AROUND THE CIRCULATION OVER THE WESTERN
SEMICIRCLE.  DVORAK DATA T-NUMBERS ARE 2.5 FROM BOTH TAFB AND SAB
SUPPORTING A CURRENT INTENSITY ESTIMATE OF 35 KT.  THEREFORE THE
SYSTEM IS BEING NAMED AT THIS TIME.  COLIN IS EXPECTED TO BE IN AN
ENVIRONMENT CONDUCIVE FOR SOME STRENGTHENING...WITH MODERATE TO
WEAK VERTICAL SHEAR AND ANTICYCLONIC UPPER-LEVEL FLOW...FOR THE
NEXT 36 HOURS OR SO.  THEREAFTER...INCREASING WESTERLY SHEAR
ASSOCIATED WITH AN UPPER-LEVEL LOW OVER THE SOUTHWESTERN NORTH
ATLANTIC SHOULD BEGIN TO IMPACT THE STORM.  THE OFFICIAL FORECAST
CALLS FOR MODEST STRENGTHENING DURING THE NEXT 36 HOURS FOLLOWED BY
A LEVELING OFF OF INTENSITY THEREAFTER.  THIS IS SIMILAR TO THE
LATEST GFDL MODEL FORECAST AND NOT TOO DISSIMILAR TO THE PREVIOUS
NHC FORECAST.  NONE OF THE DYNAMICAL OR STATISTICAL/DYNAMICAL
INTENSITY GUIDANCE BRINGS COLIN TO HURRICANE STRENGTH OVER THE NEXT
5 DAYS.
 
CENTER FIXES SHOW THAT THE STORM CONTINUES TO MOVE BRISKLY TOWARD
THE WEST-NORTHWEST...AND THE INITIAL MOTION ESTIMATE REMAINS AT
285/20.  AT THIS TIME...THE STEERING FOR COLIN IS BEING PROVIDED DUE
TO A SUBTROPICAL RIDGE TO THE NORTH AND A LOW- TO MID-TROPOSPHERIC
EASTERLY JET.  THIS RELATIVELY FAST STEERING CURRENT SHOULD MORE OR
LESS PREVAIL FOR THE NEXT COUPLE OF DAY OR SO.  THEREAFTER...THE
TROPICAL CYCLONE IS LIKELY TO APPROACH A WEAKNESS IN THE
SUBTROPICAL RIDGE.  THIS WOULD CAUSE A GRADUAL TURN TO THE RIGHT
ALONG WITH A DECREASING FORWARD SPEED.  THE TRACK GUIDANCE MODELS
ARE IN FAIRLY GOOD AGREEMENT OVER THE NEXT 36 HOURS.  AFTER THAT
FORECAST TIME...THE MODELS BECOME MODERATELY DIVERGENT WITH THE GFS
AND ECMWF ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE AND THE GFDL
AND HWRF ON THE RIGHT.  THE OFFICIAL TRACK FORECAST IS ROUGHLY IN
THE MIDDLE OF THE ENVELOPE...FAIRLY CLOSE TO THE DYNAMICAL MODEL
CONSENSUS...AND VERY CLOSE TO THE PREVIOUS NHC FORECAST.

OBSERVATIONS FROM NOAA DATA BUOY 41041 OVER THE CENTRAL TROPICAL
ATLANTIC INDICATE THAT COLIN IS A SMALL TROPICAL STORM...AND THE
WIND RADII SHOWN IN THE ADVISORY MIGHT BE GENEROUS.

INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD FOLLOW THE PROGRESS
OF COLIN.  AT THIS TIME...BASED ON THE FORECAST TRACK...WIND
FIELD...AND REASONABLE UNCERTAINTIES...NO TROPICAL STORM WATCHES OR
WARNINGS ARE REQUIRED.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0900Z 14.0N  47.2W    35 KT
 12HR VT     03/1800Z 15.1N  50.3W    40 KT
 24HR VT     04/0600Z 16.8N  54.5W    45 KT
 36HR VT     04/1800Z 18.6N  58.3W    50 KT
 48HR VT     05/0600Z 20.6N  61.5W    50 KT
 72HR VT     06/0600Z 24.5N  66.5W    50 KT
 96HR VT     07/0600Z 28.0N  68.5W    50 KT
120HR VT     08/0600Z 31.0N  69.5W    50 KT
 
$$
FORECASTER PASCH
 
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