ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM HURRICANE JUAN DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SUN SEP 28 2003 CLOUD TOPS AROUND THE EYE HAVE COOLED...WITH SOME TOPS COLDER THAN -75C...AND DVORAK CLASSIFICATIONS REMAIN T5.0...OR 90 KT...FROM BOTH TAFB AND SAB. THE EYE HAS ALSO DECREASED IN SIZE AND THE 3-HR AVERAGE DVORAK OBJECTIVE T-NUMBER IS T4.9...OR 88 KT. THEREFORE... THE INITIAL INTENSITY REMAINS AT 90 KT FOR THIS ADVISORY. THE INITIAL MOTION ESTIMATE IS 355/10...EVEN THOUGH THE PAST 6-HR MOTION HAS BEEN 340/09. THE LAST FEW SATELLITE POSITIONS...ALONG WITH WATER VAPOR MOTIONS...SUGGEST THAT JUAN MAY BE FINALLY MAKING THE TURN MORE TOWARD THE NORTH THAT THE GLOBAL MODELS HAVE BEEN FORECASTING THE PAST 24 HOURS. THERE IS A SLIGHT CONFLICT BETWEEN THE VARIOUS MODELS WITH THE GFS AND CANADIAN MODELS BRINGING A SURFACE LOW CENTER WEST OF NOVA SCOTIA AND INTO EXTREME EASTERN MAINE...WHILE THE UKMET...GFDL...AND NOGAPS MODELS TAKE JUAN OVER OR JUST WEST OF HALIFAX NOVA SCOTIA. HOWEVER...THE CANADIAN AND GFS 850-500 MB VORTICITY CENTERS ARE FORECAST TO REMAIN VERTICALLY STACKED AND PASS JUST WEST OF HALIFAX IN ABOUT 18-21 HOURS...SO THE OFFICIAL FORECAST TRACK WAS ONLY NUDGED SLIGHTLY TO THE EAST OF THE PREVIOUS FORECAST TRACK. THIS IS CONSISTENT WITH ALL OF THE MODELS FORECASTING THE 500-200 MB MEAN WIND FLOW TO BE FROM A SOUTH TO SOUTH-SOUTHWESTERLY DIRECTION AFTER 12 HOURS...WHICH SHOULD KEEP JUAN MOVING IN A GENERAL NORTHERLY DIRECTION. NOTE...AN 18-HR/00Z FORECAST POSITION WOULD PLACE JUAN NEAR 43.3N 64.2W AND 70-KT. SINCE JUAN IS FORECAST TO BEGIN ACCELERATING LATER THIS MORNING AND UNTIL LANDFALL...THERE WILL LIKELY NOT BE ANY SIGNIFICANT INCREASE IN THE VERTICAL SHEAR. THEREFORE...THE WEAKENING TREND THAT IS FORECAST IS MAINLY DUE TO THE CYCLONE PASSING OVER MUCH COOLER SSTS NORTH OF 40N LATITUDE. ALSO...THE COOLER WATER MAY CAUSE THE BOUNDARY LAYER TO BECOME MORE STABLE...WHICH MAY NOT ALLOW ALL OF THE STRONGER WINDS ALOFT TO COME DOWN TO THE SURFACE. HOWEVER... JUAN IS STILL EXPECTED TO BE NEAR HURRICANE STRENGTH AT LANDFALL. SINCE JUAN IS EXPECTED TO MAKE LANDFALL IN THE VICINITY OF HALIFAX BETWEEN 00-03Z THIS EVENING AT ASTRONOMICAL HIGH TIDE...SOME STORM SURGE FLOODING MAY OCCUR ALONG THE SOUTH COAST OF NOVA SCOTIA ...ESPECIALLY IN HARBORS AND INLETS IN AND AROUND HALIFAX. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 28/0900Z 37.6N 64.1W 90 KT 12HR VT 28/1800Z 40.7N 64.3W 80 KT 24HR VT 29/0600Z 46.0N 63.9W 60 KT...INLAND BECOMING E.T. 36HR VT 29/1800Z 53.8N 62.9W 40 KT...EXTRATROPICAL 48HR VT 30/0600Z...ABSORBED BY LARGER EXTRATROPICAL LOW NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:59 UTC