ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NICHOLAS DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT SAT OCT 18 2003 IN A BIT OF A SUNRISE SURPRISE...MORNING VISIBLE IMAGERY SHOWS THE CENTER OF NICHOLAS IS LOCATED SOUTHEAST OF THE PREVIOUS ADVISORY POSITION...WHICH REQUIRES A RE-LOCATION. THE CENTER HAS BECOME EXPOSED AS MODERATE/STRONG SOUTHWESTERLY VERTICAL SHEAR HAS DISRUPTED THE CDO PATTERN SEEN EARLIER. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM SAB...AND 65 KT FROM TAFB AND AFWA. THE INITIAL INTENSITY REMAINS 55 KT...ALTHOUGH WITH THE CURRENT APPEARANCE THIS MAY BE GENEROUS. WITH THE RE-LOCATION...THE INITIAL MOTION IS A HIGHLY UNCERTAIN 015/3. SURFACE OBSERVATIONS SUGGEST SOME STRENGTHENING OF THE 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 44W SOUTH OF 22N. 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 REMAINS SPREAD. THE GFS TAKES NICHOLAS WESTWARD...WHILE THE NOGAPS MOVES IT DUE NORTHWARD. THE UKMET AND THE GFDL CALL FOR A GENERAL NORTHWESTWARD MOTION THROUGH 72 HR...AND THE FORECAST TRACK THROUGH THAT TIME IS IN BEST AGREEMENT WITH THEM. AFTER 120 HR...THE FORECAST TRACK CALLS FOR A CONTINUED NORTHWEST MOTION. HOWEVER...A LARGE NON-TROPICAL CYCLONE DEVELOPING OFF THE U.S. EAST COAST COULD CAUSE NICHOLAS TO TURN MORE NORTHWARD THAN CURRENTLY FORECAST. WHILE NICHOLAS SHOWS ANTICYCLONIC OUTFLOW EVEN TO THE SOUTHWEST... THE FLOW ASSOCIATED WITH THE UPPER-LEVEL RIDGE IS UNDERCUTTING THE OUTFLOW AND SHEARING THE STORM. THE LARGE-SCALE MODELS CONTINUE TO FORECAST A SHORT-TERM DECREASE IN THE SHEAR. SO FAR...THESE FORECASTS HAVE NOT VERIFIED...AND THERE ARE NO OBVIOUS SIGNS THAT THEY ARE GOING TO VERIFY NOW. THE INTENSITY FORECAST IS BASED ON THE PREMISE THAT CONTINUED MODERATE/STRONG WESTERLY SHEAR WILL CONTINUE THROUGH THE FORECAST PERIOD AND CAUSE GRADUAL WEAKENING. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 18/1500Z 16.9N 47.7W 55 KT 12HR VT 19/0000Z 17.4N 47.8W 55 KT 24HR VT 19/1200Z 18.1N 48.2W 50 KT 36HR VT 20/0000Z 18.8N 48.8W 50 KT 48HR VT 20/1200Z 19.5N 49.6W 45 KT 72HR VT 21/1200Z 20.5N 51.0W 40 KT 96HR VT 22/1200Z 21.5N 52.5W 35 KT 120HR VT 23/1200Z 22.5N 54.0W 30 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:50:00 UTC