846
WTNT42 KNHC 110240
TCDAT2
HURRICANE FRED DISCUSSION NUMBER 14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072009
1100 PM AST THU SEP 10 2009
SOUTHWESTERLY SHEAR CONTINUES TO DISRUPT THE STRUCTURE OF FRED. A
COMPARISON OF THE 37- AND 85-GHZ CHANNEL IMAGERY FROM A 2212 UTC
TRMM PASS INDICATES THAT THE MID-LEVEL CENTER OF ROTATION IS
DISPLACED ABOUT 20-25 N MI NORTH OF THE LOW-LEVEL CENTER...AND THE
MID-LEVEL REMNANT EYEWALL IS COMPLETELY ERODED ON THE SOUTHERN
SIDE. THIS PATTERN HAS YIELDED DVORAK CURRENT INTENSITY ESTIMATES
OF 77 KT FROM BOTH TAFB AND SAB...SO THE INITIAL INTENSITY IS
DECREASED TO 75 KT FOR THIS ADVISORY. ALL OF THE INTENSITY GUIDANCE
GRADUALLY WEAKENS FRED DUE TO 20-30 KT OF SOUTHWESTERLY SHEAR AND
MARGINALLY WARM SEA SURFACE TEMPERATURES OVER THE NEXT 48 HOURS...
WITH EVEN STRONGER SHEAR AFTER THAT. THERE IS VERY LITTLE SPREAD IN
THE INTENSITY MODELS...AND THE NHC FORECAST CALLS FOR FRED TO
WEAKEN TO A TROPICAL STORM BY 24 HOURS AND ULTIMATELY A REMNANT LOW
BY DAY 4.
THE STEERING CURRENTS AROUND FRED ARE BEGINNING TO COLLAPSE AND THE
INITIAL MOTION IS ESTIMATED AT 350 DEGREES AT 3 KT. ONLY A SLOW
NORTH TO NORTH-NORTHEASTWARD DRIFT IS EXPECTED DURING THE NEXT 48
HOURS AS FRED TEMPORARILY RESPONDS TO A MID-LEVEL TROUGH TO ITS
NORTH. ONCE IT WEAKENS AND BECOMES A SHALLOWER SYSTEM...THE
CYCLONE IS EXPECTED TO TURN NORTHWESTWARD AND WEST-NORTHWESTWARD
WITH AN INCREASE IN FORWARD SPEED UNDER THE INFLUENCE OF THE
LOW-LEVEL SUBTROPICAL RIDGE. THE NEW OFFICIAL FORECAST IS SLIGHTLY
EAST OF THE PREVIOUS TRACK DURING THE FIRST 48 HOURS BUT DOES NOT
SHOW AS MUCH OF AN EASTWARD BEND AS THE TVCN MODEL CONSENSUS.
STILL...THE MOTION WILL BE SLOW...AND FRED COULD MEANDER A BIT
DURING THE FIRST COUPLE OF DAYS OF THE FORECAST PERIOD BEFORE
ACCELERATING NORTHWESTWARD AFTER 72 HOURS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 11/0300Z 17.4N 35.1W 75 KT
12HR VT 11/1200Z 17.7N 35.0W 65 KT
24HR VT 12/0000Z 17.9N 34.9W 55 KT
36HR VT 12/1200Z 18.0N 34.8W 45 KT
48HR VT 13/0000Z 18.3N 34.7W 35 KT
72HR VT 14/0000Z 20.0N 36.5W 30 KT
96HR VT 15/0000Z 21.5N 41.0W 25 KT...REMNANT LOW
120HR VT 16/0000Z 23.0N 45.5W 20 KT...REMNANT LOW
FORECASTER BERG
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