Tropical Storm NICHOLAS

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TROPICAL STORM NICHOLAS DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT SAT OCT 18 2003
 
NICHOLAS CONTINUES TO BE STRONGLY SHEARED FROM THE SOUTHWEST...BUT
ALSO IS MAINTAINING A COLD CDO AND BANDING AS WELL AS GOOD OUTFLOW
ALOFT.  DVORAK T NUMBERS HAVE DECREASED A LITTLE...BUT STILL
SUPPORT AN INITIAL WIND SPEED OF 55 KT.  THE OFFICIAL FORECAST IS
FOR SLOW WEAKENING UNDER CONTINUED STRONG VERTICAL SHEAR FOLLOWING
THE SHIPS MODEL.  IN CONTRAST...THE GFDL MODEL KEEPS FORECASTING
NICHOLAS TO A HURRICANE.  

IT HARD TO LOCATE THE LOW-LEVEL CENTER.  THE LATEST MICROWAVE IMAGES
SHOW A POORLY DEFINED LOW LEVEL CLOUD PATTERN.  THE STORM IS
LOCATED BY ASSUMING THAT THE CENTER IS NEAR THE SOUTHWEST EDGE OF
THE DEEP CONVECTION.  THIS GIVES AN INITIAL MOTION ESTIMATE OF
340/05.

THE GFS MODEL KEEPS A MID-LEVEL RIDGE NORTH OF NICHOLAS AND SHOWS A
SLOW WESTWARD MOTION FOR 120 HOURS.  THE ECMWF MODEL SHOWS A
SIMILAR BEHAVIOR.  THE GFDL...NOGAPS AND UKMET MODELS SHOW A SLOW
MOSTLY NORTHWARD MOTION WITH THE RIDGE SHIFTING EASTWARD AS
VIGOROUS SHORT-WAVE TROUGHS GRADUALLY PUSH EASTWARD FROM NORTH
AMERICA.  THE OFFICIAL FORECAST TRACK IS A COMPROMISE OF THE
WESTWARD AND NORTHWARD SCENARIOS MOVING THE STORM SLOWLY
NORTHWESTWARD FOR 120 HOURS.

FORECASTER LAWRENCE
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/0900Z 17.3N  48.5W    55 KT
 12HR VT     18/1800Z 17.9N  48.7W    55 KT
 24HR VT     19/0600Z 18.4N  49.3W    55 KT
 36HR VT     19/1800Z 19.0N  49.8W    50 KT
 48HR VT     20/0600Z 19.6N  50.4W    50 KT
 72HR VT     21/0600Z 20.6N  51.6W    45 KT
 96HR VT     22/0600Z 21.5N  53.0W    40 KT
120HR VT     23/0600Z 22.5N  54.5W    35 KT
 
 
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