011
WTNT42 KNHC 110848
TCDAT2
HURRICANE FRED DISCUSSION NUMBER 15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009
500 AM AST FRI SEP 11 2009
THERE HAS NOT BEEN ANY RECENT MICROWAVE IMAGERY OVER FRED...SO IT
HAS BEEN DIFFICULT TO DIAGNOSE ANY STRUCTURAL CHANGES. OVERALL...
CONVECTION REMAINS QUITE STRONG NEAR THE MID-LEVEL CENTER...WITH
DVORAK INTENSITY ESTIMATES HOLDING STEADY NEAR 77 KT. YET
SATELLITE IMAGERY SHOWS THAT THE CLOUD PATTERN IS BECOMING
ELONGATED FROM THE SOUTHWEST TO NORTHEAST...WITH EVEN SOME HINTS
THAT THE LOW-LEVEL CENTER IS WELL SOUTHWEST OF THE MID-LEVEL
CENTER. FOR NOW...THE INITIAL WIND SPEED IS HELD AT 75 KT...BUT
THAT ESTIMATE COULD BE A LITTLE HIGH. THE INTENSITY FORECAST
APPEARS STRAIGHTFORWARD WITH 20-30 KT OF SOUTHWESTERLY SHEAR LIKELY
CAUSING STEADY WEAKENING OVER THE NEXT 48 HOURS...WITH EVEN STRONGER
SHEAR THEREAFTER. ALTHOUGH SSTS ARE MARGINALLY WARM...THE EXPECTED
SLOW MOTION OF FRED SHOULD CAUSE UPWELLING OF COOLER WATERS AND
HELP TO DIMINISH CONVECTION NEAR THE CENTER. THE NHC FORECAST
CONTINUES THE TREND OF THE PREVIOUS FORECAST AND IS SIMILAR TO THE
SHIPS MODEL.
IT APPEARS THAT FRED HAS TURNED TOWARD THE NORTH OR 000/3.
LITTLE NET MOTION IS EXPECTED OVER THE NEXT DAY OR TWO WITH A
MID-LEVEL TROUGH TO ITS NORTHWEST PERHAPS NUDGING THE TROPICAL
CYCLONE A LITTLE NORTHEASTWARD. ONCE FRED WEAKENS INTO A
SHALLOWER SYSTEM...THE CYCLONE SHOULD TURN NORTHWESTWARD AND
WEST-NORTHWESTWARD WITH AN INCREASE IN FORWARD SPEED UNDER THE
INFLUENCE OF A REBUILDING SURFACE RIDGE. THE OFFICIAL FORECAST IS
CLOSE TO THE PREVIOUS ONE THROUGH 48 HR THEN IS SHIFTED TO THE WEST
AFTERWARDS...A LITTLE SOUTH OF THE MODEL CONSENSUS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 11/0900Z 17.7N 35.1W 75 KT
12HR VT 11/1800Z 17.9N 35.0W 60 KT
24HR VT 12/0600Z 18.0N 34.8W 50 KT
36HR VT 12/1800Z 18.2N 34.6W 40 KT
48HR VT 13/0600Z 18.6N 34.7W 35 KT
72HR VT 14/0600Z 20.0N 37.5W 25 KT
96HR VT 15/0600Z 21.5N 42.0W 20 KT...REMNANT LOW
120HR VT 16/0600Z 22.5N 47.5W 20 KT...REMNANT LOW
FORECASTER BLAKE
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