ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM 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 NNNN
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Page last modified: Monday, 07-Feb-2005 16:50:00 UTC