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Tropical Storm NICHOLAS

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TROPICAL STORM NICHOLAS DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT WED OCT 15 2003

NICHOLAS IS GIVING MIXED SIGNALS THIS MORNING.  ON ONE SIDE...
VISIBLE IMAGERY SUGGESTS THE SYSTEM IS FORMING A CENTRAL DENSE
OVERCAST WITH AN OUTER BAND AND AN OUTFLOW-LEVEL ANTICYCLONE.  ON
THE OTHER...ANIMATION AND A 1041Z SSM/I OVERPASS SUGGESTS THAT THE
LOW-LEVEL CENTER IS PARTLY EXPOSED SOUTHWEST OF THE CONVECTIVE
OVERCAST...POSSIBLY IN RESPONSE TO WESTERLY FLOW UNDERCUTTING THE
OUTFLOW.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND
SAB...AND 35 KT FROM AFWA.  THE INITIAL INTENSITY REMAINS 45 KT. 
IF THE LOW-LEVEL CENTER IS UNDER THE OVERCAST THE CYCLONE COULD BE
STRONGER...AND THERE IS A CHANCE THAT THE CENTER COULD REFORM UNDER
THE CONVECTION.
 
THE INITIAL MOTION IS A LITTLE SLOWER THAN PREVIOUSLY...295/7. 
NICHOLAS IS ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE...AND WATER
VAPOR IMAGERY SHOWS A MID/UPPER-LEVEL ANTICYCLONE NEAR 23N52W
SANDWICHED BETWEEN A DEEP-LAYER CIRCULATION NEAR 27N36W AND A
MID/UPPER-LEVEL SHORTWAVE NORTH OF THE LESSER ANTILLES. 
LARGE-SCALE MODELS SUGGEST THAT THE SHORTWAVE WILL TEMPORARILY
WEAKEN THE RIDGE NORTH OF NICHOLAS IN THE SHORT TERM...FOLLOWED BY
REBUILDING RIDGING NORTH OF THE STORM AFTER THE SHORTWAVE PASSES IN
48-72 HR.  THE TRACK GUIDANCE SHOWS A CONSIDERABLE SPREAD...WITH
THE GFS...NOGAPS...AND GFDL SHOWING A NORTHWARD MOTION AFTER 24
HR...THE UKMET SHOWING A NORTHWESTWARD MOTION...AND THE NHC98 AND
BAMM SHOWING A WEST-NORTHWESTWARD MOTION.  BASED ON CURRENT
TRENDS...THE GFS...NOGAPS...AND GFDL TURN NICHOLAS TOO MUCH INTO
THE RIDGE...SO THE FORECAST TRACK WILL LEAN TOWARD THE
MIDDLE-OF-THE-ROAD UKMET.  THE OFFICIAL FORECAST CALLS FOR A
GRADUAL TURN TOWARD THE NORTHWEST DURING THE NEXT 24 HR...FOLLOWED
BY A TURN TOWARD THE WEST-NORTHWEST AFTER 72 HR.

LARGE-SCALE MODELS SUGGEST THAT THE WESTERLY SHEAR NOW AFFECTING
NICHOLAS SHOULD GRADUALLY DECREASE OVER THE NEXT 72 HR AS A
SYNTOPIC-SCALE ANTICYCLONE FORMS OVER THE CYCLONE.  SHOULD THIS
VERIFY...IT WOULD ALLOW STRENGTHENING AS SHOWN IN THE INTENSITY
FORECAST.  INCREASING SHEAR AFTER 72 HR SHOULD LIMIT
INTENSIFICATION.  THE INTENSITY FORECAST REMAINS A COMPROMISE
BETWEEN THE WEAKER SHIPS AND THE STRONGER GFDL.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/1500Z 11.9N  43.9W    45 KT
 12HR VT     16/0000Z 12.5N  44.9W    50 KT
 24HR VT     16/1200Z 13.5N  46.1W    55 KT
 36HR VT     17/0000Z 14.7N  47.0W    60 KT
 48HR VT     17/1200Z 16.0N  47.6W    65 KT
 72HR VT     18/1200Z 17.5N  48.5W    70 KT
 96HR VT     19/1200Z 18.0N  49.5W    70 KT
120HR VT     20/1200Z 18.5N  51.0W    70 KT
 
 
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