Tropical Storm NICHOLAS

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TROPICAL STORM NICHOLAS DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT FRI OCT 17 2003
 
SATELLITE IMAGERY SHOWS SOUTHWESTERLY VERTICAL WIND SHEAR IMPINGING
ON THE STORM...YET A COLD CDO FEATURE PERSISTS AND...ALONG WITH SOME
BANDING...RESULTS IN DVORAK WIND SPEED ESTIMATES OF 55 KNOTS FROM
ALL AGENCIES.  THIS IS NO CHANGE FROM THE PREVIOUS ADVISORY.  THE
SHIPS FORECASTS GRADUAL WEAKENING FRO 120 HOURS WITH LOTS OF
VERTICAL SHEAR WEAKENING SOME AFTER 48 HOURS.  ONLY THE GFDL MODEL
SUGGESTS THE POSSIBILITY OF REACHING 65 KNOTS.  THE OFFICIAL
FORECAST BACKS OFF 5 KNOTS FROM THE PREVIOUS ADVISORY AFTER 12
HOURS TO AGREE MORE WITH THE SHIPS MODEL.
 
THE LOW-LEVEL CENTER IS STILL IMPOSSIBLE TO LOCATE ON INFRARED
IMAGERY.  EARLIER ANALYSES PLACED THE LOW LEVEL CENTER NEAR THE
SOUTHWESTERN EDGE OF THE DEEP CONVECTION.  THE CURRENT POSITION
ESTIMATE IS BASED ON THE SAME PROCEDURE AND GIVES AN INITIAL MOTION
ESTIMATE OF 310/07.  THE GUIDANCE HAS NOT CHANGED MUCH.  THE GFS
AND UKMET CONTINUE TO  SHOW A SLOW NORTHWESTWARD MOTION FOR 120
HOURS WHILE THE GFDL AND NOGAPS SHOW A SLOW MOSTLY NORTHWARD
MOTION.  WHICH FORECAST IS CORRECT DEPENDS ON THE INTENSITY WITH A
WEAKER CYCLONE HAVING MORE WESTWARD COMPONENT OF MOTION LIKE THE
GFS AND UKMET MODELS.  THE OFFICIAL FORECAST IS ADJUSTED SLIGHTLY
TO THE RIGHT OF THE PREVIOUS ADVISORY TO GET CLOSER TO A CONSENSUS
OF THE MODELS BUT THE OFFICIAL FORECAST STILL LEANS TOWARD THE
WEAKER CYCLONE SCENARIO.

WIND SPEED RADII HAVE BEEN INCREASED BASED ON A RECENT QUIKSCAT
PASS.

FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 15.0N  48.0W    55 KT
 12HR VT     17/1800Z 15.9N  48.7W    55 KT
 24HR VT     18/0600Z 16.8N  49.2W    55 KT
 36HR VT     18/1800Z 17.6N  49.9W    60 KT
 48HR VT     19/0600Z 18.4N  50.6W    60 KT
 72HR VT     20/0600Z 19.3N  51.5W    55 KT
 96HR VT     21/0600Z 20.5N  52.5W    50 KT
120HR VT     22/0600Z 21.5N  53.5W    45 KT
 
 
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