Tropical Storm ISAAC

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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
 
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FORECASTER AVILA
 
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