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