ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GRACE DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092009 1100 PM AST SUN OCT 04 2009 CONVECTIVE ACTIVITY ASSOCIATED WITH THE LOW PRESSURE AREA NORTHEAST OF THE AZORES ISLANDS HAS BECOME BETTER ORGANIZED THIS EVENING. THE CONVECTION...WHICH HAS SHOWN SOME ORGANIZATION FOR MUCH OF THE DAY...IS RELATIVELY DEEP AND SURROUNDS AN EYE-LIKE FEATURE THAT HAS PERSISTED FOR SEVERAL HOURS. THIS IS THE SAME SURFACE LOW PRESSURE AREA THAT MOVED THROUGH THE AZORES SEVERAL DAYS AGO AND MADE A COUNTER-CLOCKWISE LOOP. THE LOW...PREVIOUSLY ASSOCIATED WITH AN OCCLUDED FRONT AND CO-LOCATED WITH AN UPPER LOW...HAS SINCE LOST ITS FRONTAL STRUCTURE AND IS NOW LOCATED UNDER A FAIRLY UNIFORM SOUTHWESTERLY UPPER FLOW. IN ADDITION...2210Z ASCAT DATA INDICATED A VERY SMALL RADIUS OF MAXIMUM WIND...LESS THAN 20 MILES. WITH THESE STRUCTURAL CHANGES...THE SYSTEM CAN NOW BE CLASSIFIED AS A TROPICAL STORM. THE ASCAT PASS SHOWED A COUPLE OF 45-50 KT WIND VECTORS TO THE SOUTHEAST OF THE CENTER...AND THESE DATA ARE THE BASIS FOR THE 55 KT INITIAL INTENSITY. GRACE IS CURRENTLY OVER SSTS AROUND 21 DEGREES CELSIUS AND WITHIN AN UPPER-LEVEL ENVIRONMENT CHARACTERIZED BY LIGHT TO MODERATE SOUTHWESTERLY SHEAR. ALTHOUGH THE SHEAR IS NOT FORECAST TO INCREASE DURING THE NEXT DAY OR TWO...THE CYCLONE IS HEADED FOR EVEN COLDER WATER AND WILL LIKELY BEGIN TO WEAKEN VERY SOON. THE GLOBAL MODELS SUGGEST THAT THE SMALL CYCLONE WILL BE ABSORBED BY A LARGER EXTRATROPICAL CYCLONE OVER THE NORTHEASTERN ATLANTIC IN ABOUT 36 HOURS...IF NOT SOONER. GRACE IS MOVING NORTHEASTWARD IN THE DEEP LAYER SOUTHWESTERLY FLOW OVER THE NORTHEASTERN ATLANTIC. A GENERAL NORTHEASTWARD MOTION IS EXPECTED TO CONTINUE UNTIL DISSIPATION. FORECAST POSITIONS AND MAX WINDS INITIAL 05/0300Z 41.2N 20.3W 55 KT 12HR VT 05/1200Z 44.0N 18.0W 50 KT 24HR VT 06/0000Z 48.0N 16.0W 45 KT 36HR VT 06/1200Z...DISSIPATED $$ FORECASTER BROWN/FRANKLIN NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:11 UTC