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TROPICAL STORM KAREN DISCUSSION NUMBER 4
NATIONAL WEATHER SERVICE MIAMI FL
11 AM EDT SAT OCT 13 2001
DVORAK TROPICAL CYCLONE INTENSITY ESTIMATES FROM TAFB AND SAB ARE
NOW AT 60 KTS...WHICH WILL BE THE INITIAL INTENSITY. IF THE DEEP
CONVECTION CONTINUES TO WRAP AROUND ON THE EAST SIDE OF THE SYSTEM
THEN KAREN COULD BECOME A HURRICANE LATER TODAY. THIS... AND THE
FACT THAT THE SHIPS MODEL TAKES KAREN VERY NEAR HURRICANE FORCE IN
12 HOURS IS THE BASIS FOR FORECASTING THE SYSTEM TO 65 KTS. THE
SYSTEM WILL BEGIN MOVING OVER COLDER WATERS AFTER 12 HOURS AND
WEAKENING IS FORECAST.
THE INITIAL MOTION IS ADJUSTED TO 015/12. KAREN IS SLOWLY
ACCELERATING AS IT IS EMBEDDED IN AN AREA OF DEEP-LAYER
SOUTH-SOUTHWEST FLOW BETWEEN A RIDGE OVER THE CENTRAL ATLANTIC AND
STRONGER FLOW ASSOCIATED WITH STRONG TROUGHING OVER THE UNITED
STATES. MODEL GUIDANCE IS IN REASONABLE AGREEMENT IN THE DIRECTION
OF MOTION OF THE SYSTEM BUT VARIES IN SPEED OF MOTION. DISCUSSIONS
WITH HPC SUGGEST THAT THE GLOBAL MODELS DO NOT REFLECT THE CORRECT
INITIAL MOTION AND THAT THEY ARE SLOW. THIS IS TAKEN INTO ACCOUNT
IN THE OFFICIAL FORECAST.
WIND RADII AND THE 12 FOOT SEAS WERE ADJUSTED BASED UPON QUIK-SCAT
DATA AND SHIP OBSERVATIONS.
FORECASTER JARVINEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 13/1500Z 37.0N 64.5W 60 KTS
12HR VT 14/0000Z 38.7N 63.8W 65 KTS
24HR VT 14/1200Z 41.0N 62.5W 65 KTS
36HR VT 15/0000Z 43.5N 61.0W 55 KTS
48HR VT 15/1200Z 46.0N 59.0W 40 KTS
72HR VT 16/1200Z 50.0N 53.0W 30 KTS...EXTRATROPICAL
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