ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NICHOLAS DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT SAT OCT 18 2003 AS HAS HAPPENED THE PAST TWO AFTERNOONS...A NEW BURST OF CONVECTION HAS DEVELOPED OVER THE LOW-LEVEL CENTER OF NICHOLAS. HOWEVER...THE STORM LOOKS A LITTLE LESS ORGANIZED THAN IT DID 24 HR AGO...AND SATELLITE INTENSITY ESTIMATES HAVE DECREASED...ESPECIALLY FROM TAFB. THIS DECREASE IS SUPPORTED BY EXPERIMENTAL INTENSITY ESTIMATES FROM ADVANCED MICROWAVE SOUNDING UNIT DATA FROM THE NOAA POLAR ORBITING SATELLITES. THE MAXIMUM WINDS ARE REDUCED TO 50 KT. THE INITIAL MOTION IS NOW 360/3. SURFACE OBSERVATIONS SHOW A LOW-LEVEL RIDGE NORTH OF NICHOLAS...WHILE WATER VAPOR IMAGERY SHOWS A LARGE MID/UPPER-LEVEL RIDGE DEVELOPING OVER THE CENTRAL ATLANTIC AS A LARGE TROUGH DEVELOPS OVER THE WESTERN ATLANTIC AND EASTERN UNITED STATES. ADDITIONALLY...A BROAD UPPER-LEVEL RIDGE IS ALONG 45W SOUTH OF 21N. THIS COMPLEX PATTERN WILL LIKELY CONTINUE THE SLOW MOTION OF NICHOLAS...AND THE BUILDING RIDGE TO THE NORTH SUGGESTS THE CYCLONE SHOULD RESUME A MORE WESTWARD TRACK IN THE NEXT 24-36 HR. TRACK GUIDANCE IS A LITTLE LESS SPREAD THAN EARLIER...AS THE NOGAPS...GFDL...AND UKMET NOW GENERALLY AGREE ON A NORTHWESTWARD TO NORTHWARD MOTION. EVEN THE WESTWARD-POINTING GFS NOW SHOWS A MORE NORTHWARD TURN BY THE END OF THE FORECAST PERIOD IN RESPONSE TO A DEVELOPING NON-TROPICAL CYCLONE OFF THE U.S. EAST COAST. THE OFFICIAL FORECAST NOW CALLS FOR A TURN TOWARD THE NORTHWEST DURING THE FIRST 24 HR....THEN A TURN TOWARD THE NORTH-NORTHWEST AFTER 72 HR. NICHOLAS NOW SHOWS NO OUTFLOW OVER THE WESTERN SEMICIRCLE AS SOUTHWESTERLY TO WESTERLY SHEAR CONTINUES TO IMPACT IT. THE LARGE-SCALE MODELS CONTINUE TO FORECAST A SHORT-TERM DECREASE IN SHEAR THAT HAS JUST NOT OCCURRED. THE INTENSITY FORECAST WILL CONTINUE TO BE BASED ON THE PREMISE THAT MODERATE/STRONG WESTERLY SHEAR WILL LAST THROUGH THE FORECAST PERIOD AND CAUSE GRADUAL WEAKENING. IT SHOULD BE NOTED THAT THE MODELS FORECAST A SHORTWAVE TROUGH NOW OVER THE EASTERN CARIBBEAN TO MOVE EAST-NORTHEAST AND INTERACT WITH NICHOLAS. HOWEVER...THE DETAILS DIFFER ENOUGH BETWEEN THE MODELS THAT IT IS NOT CURRENTLY POSSIBLE TO TELL WHETHER THIS WILL HELP THE STORM OR HURT IT. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 18/2100Z 17.3N 47.7W 50 KT 12HR VT 19/0600Z 17.7N 47.9W 50 KT 24HR VT 19/1800Z 18.4N 48.4W 45 KT 36HR VT 20/0600Z 19.1N 49.1W 45 KT 48HR VT 20/1800Z 19.7N 49.7W 40 KT 72HR VT 21/1800Z 21.0N 51.0W 40 KT 96HR VT 22/1800Z 22.5N 52.0W 35 KT 120HR VT 23/1800Z 24.5N 53.0W 30 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:50:00 UTC