ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IGOR DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 500 AM AST THU SEP 09 2010 THE CLOUD PATTERN HAS DETERIORATED DURING THE PAST 6 HOURS AND CONTINUES TO BE HIGHLY SHEARED. NEITHER SATELLITE INTENSITY ESTIMATES NOR ASCAT MEASUREMENTS SUPPORT TROPICAL STORM INTENSITY. THE INITIAL INTENSITY HAS BEEN ADJUSTED DOWN TO 35 KNOTS AND THIS ESTIMATE IS GENEROUS. IGOR COULD WEAKEN A LITTLE MORE TODAY BUT GIVEN THAT THE CYCLONE STILL HAS A LARGE CIRCULATION AND IS MOVING TOWARD A MORE FAVORABLE ENVIRONMENT OF LOWER SHEAR AND WARMER OCEAN...A GRADUAL STRENGTHENING COULD BEGIN IN 24 HOUR OR SO. IGOR IS STILL FORECAST TO BECOME A HURRICANE IN ABOUT 3 DAYS. FIRST VISIBLE SATELLITE IMAGES INDICATE THAT THE CENTER IS STILL LOCATED SOUTH OF THE CAPE VERDE ISLANDS SUGGESTING THAT IGOR HAS BEEN MEANDERING DURING THE PAST FEW HOURS. HOWEVER...THE LARGE CIRCULATION SHOULD BEGIN TO MOVE SLOWLY TOWARD THE WEST-NORTHWEST LATER TODAY. THE STEERING PATTERN OVER THE ATLANTIC HAS BEEN QUITE PERSISTENT AND CONSISTS OF A SUBTROPICAL RIDGE OVER THE EASTERN PART OF THE BASIN AND A BROAD TROUGH OSCILLATING BETWEEN THE EASTERN UNITED STATES AND THE WESTERN PORTION OF THE BASIN. THIS STEERING PATTERN WHICH IS FORECAST BY THE GLOBAL MODELS TO CONTINUE...WOULD FAVOR A GENERAL WESTWARD MOTION WITH AN INCREASE IN FORWARD SPEED DURING THE NEXT DAY OR TWO AND THEN A TURN MORE TO THE WEST-NORTHWEST BY THE END OF THE FORECAST PERIOD. TRACK GUIDANCE DEPICTS THIS SCENARIO WHICH IS REFLECTED IN THE OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 09/0900Z 13.8N 24.3W 35 KT 12HR VT 09/1800Z 14.0N 25.3W 30 KT 24HR VT 10/0600Z 15.0N 28.0W 40 KT 36HR VT 10/1800Z 16.0N 31.0W 45 KT 48HR VT 11/0600Z 16.5N 34.0W 55 KT 72HR VT 12/0600Z 17.0N 40.0W 65 KT 96HR VT 13/0600Z 18.0N 44.5W 75 KT 120HR VT 14/0600Z 19.5N 49.0W 85 KT $$ FORECASTER AVILA NNNN
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Page last modified: Friday, 15-Apr-2011 12:09:14 UTC