Tropical Storm NICHOLAS

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TROPICAL STORM NICHOLAS DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT WED OCT 15 2003
 
NICHOLAS IS A LITTLE BETTER ORGANIZED THIS AFTERNOON.  THE STORM IS
MAINTINING AN ATTEMPT AT A CENTRAL DENSE OVERCAST WITH A BAND TO
THE EAST...AND THE CIRRUS OUTFLOW ANTICYCLONE IS LARGER THAN 6 HR
AGO.  THERE STILL APPEARS TO BE SOME WESTERLY VERTICAL SHEAR
UNDERCUTTING THE ANTICYCLONE...AS THE LOW-LEVEL CENTER IS STILL ON
THE WEST SIDE OF THE CONVECTIVE OVERCAST.  HOWEVER...THE SEPARATION
BETWEEN THE TWO IS SMALLER THAN THIS MORNING.  SATELLITE INTENSITY
ESTIMATES REMAIN 55 KT FROM TAFB AND SAB...AND HAVE INCREASED TO 45
KT AT AFWA.  THE INITIAL INTENSITY REMAINS 45 KT...ALTHOUGH
NICHOLAS COULD BE A LITTLE STRONGER.
 
THE INITIAL MOTION IS 295/7.  NICHOLAS REMAINS SOUTH OF A
LOW/MID-LEVEL RIDGE...AND WATER VAPOR IMAGERY SHOWS A MID/UPPER-
LEVEL ANTICYCLONE NEAR 23N50W BETWEEN A DEEP-LAYER CIRCULATION NEAR
26N35W AND A MID/UPPER-LEVEL SHORTWAVE NORTHEAST OF THE LESSER
ANTILLES.  LARGE-SCALE MODELS SUGGEST THAT THE SHORTWAVE WILL
WEAKEN THE RIDGE NORTH OF NICHOLAS IN THE SHORT TERM...FOLLOWED BY
A REBUILDING RIDGE AFTER THE SHORTWAVE PASSES IN 48-72 HR.  TRACK
GUIDANCE STILL SHOWS SHOW 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 QUICKLY INTO THE RIDGE. 
HOWEVER...ALL THE LARGE-SCALE MODELS ARE WEAKER WITH THE REBUILDING
THAN EARLIER...SO THE FORECAST TRACK SPLITS THE DIFFERENCE BETWEEN
THE UKMET AND OTHER DYNAMICAL GUIDANCE.  THE GREATEST DIFFERENCE
BETWEEN THE CURRENT AND PREVIOUS TRACKS IS A MORE NORTHERLY MOTION
NOW FORECAST AFTER 120 HR.
 
LARGE-SCALE MODELS SUGGEST THAT THE WESTERLY SHEAR NOW AFFECTING
NICHOLAS SHOULD GRADUALLY DECREASE FOR 48-72 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.

THE INITIAL AND FORECAST WIND RADII HAVE BEEN REVISED BASED ON A
SEAWINDS SCATTEROMETER OVERPASS.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 12.4N  44.5W    45 KT
 12HR VT     16/0600Z 13.0N  45.4W    50 KT
 24HR VT     16/1800Z 14.1N  46.5W    55 KT
 36HR VT     17/0600Z 15.3N  47.1W    60 KT
 48HR VT     17/1800Z 16.4N  47.7W    65 KT
 72HR VT     18/1800Z 17.5N  48.5W    70 KT
 96HR VT     19/1800Z 18.5N  49.5W    70 KT
120HR VT     20/1800Z 19.5N  51.0W    70 KT
 
 
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