ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ISAAC DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092006 1100 PM EDT FRI SEP 29 2006 THE SHAPE OF THE CLOUD PATTERN HAS BECOME A LITTLE BETTER ORGANIZED AND MORE TYPICAL OF A TROPICAL STORM. I DID NOT MAKE ISAAC A HURRICANE BECAUSE THE CONVECTION SURROUNDING THE CENTER IS NOT VERY STRONG AT THE TIME OF THIS ADVISORY...BUT I WAS VERY TEMPTED. A QUIKSCAT PASS OVER THE CYCLONE SHOWED A FEW VECTORS OF 60 KNOTS JUST TO THE NORTH OF THE CENTER. HOWEVER...I AM NOT SURE IF THESE VECTOR ARE REPRESENTATIVE OR NOT OF THE INTENSITY OF ISAAC...SINCE THERE IS ALWAYS A LOT OF GOOD DEBATE ABOUT THE SUBJECT AMONG THE QUIKSCAT EXPERTS. HOWEVER...THESE WINDS ARE ONLY 5 KNOTS ABOVE THE DVORAK INTENSITY ESTIMATES...AND I AM NOT GOING TO ARGUE OVER 5 KNOTS. SO LET'S USE THE VECTORS AND INCREASE THE WINDS TO 60 KNOTS. UNANIMOUSLY...ALL INTENSITY MODELS BRING ISAAC TO HURRICANE STATUS BEFORE THE SHEAR INCREASES AND THE OCEAN COOLS...AND SO DOES THE OFFICIAL FORECAST. ISSAC SHOULD BECOME EXTRATROPICAL IN 3 DAYS AND BECOME ABSORBED BY A LARGER FRONTAL SYSTEM IN 5 DAYS OR EARLIER. ISAAC IS MOVING TOWARD THE WEST-NORTHWEST ABOUT 7 KNOTS BUT IS ALREADY REACHING THE WESTERN PORTION OF THE SUBTROPICAL RIDGE AND THE SOUTHERLY FLOW ASSOCIATED WITH A STRONG MID-LATITUDE TROUGH. THIS PATTERN SHOULD STEER ISAAC NORTHWARD AND PASS WELL EAST OF BERMUDA IN THE NEXT DAY OR TWO. IT SHOULD THEN TURN TO THE NORTH-NORTHEAST WITH INCREASING FORWARD SPEED. ISAAC IS EXPECTED TO BE AN EXTRATROPICAL STORM WHILE APPROACHING SOUTHEASTERN NEWFOUNDLAND IN ABOUT 3 DAYS. THIS IS CONSISTENT WITH TRACK GUIDANCE WHICH IN FACT HAS SHIFTED TO THE LEFT A LITTLE BIT...AND THE MAIN ENVELOPE IS OVER EXTREME SOUTHEASTERN NEWFOUNDLAND AND ADJACENT WATERS. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0300Z 30.1N 57.4W 60 KT 12HR VT 30/1200Z 30.5N 58.4W 65 KT 24HR VT 01/0000Z 31.5N 59.7W 65 KT 36HR VT 01/1200Z 33.5N 61.0W 65 KT 48HR VT 02/0000Z 36.5N 61.0W 60 KT 72HR VT 03/0000Z 46.0N 55.0W 55 KT...EXTRATROPICAL 96HR VT 04/0000Z 51.0N 45.0W 45 KT...EXTRATROPICAL 120HR VT 05/0000Z...ABSORBED BY A FRONTAL SYSTEM $$ FORECASTER AVILA NNNN
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Page last modified: Saturday, 30-Sep-2006 02:35:01 UTC