Hurricane FRED

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HURRICANE FRED DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072009
1100 PM AST WED SEP 09 2009
 
THE EYE OF FRED COMPLETELY DISAPPEARED FROM INFRARED IMAGERY AROUND
2300 UTC...AND IT APPEARS THAT SOME SHEAR AND DRY AIR IS ERODING
THE CONVECTION IN THE SOUTHERN PART OF THE CIRCULATION.  ANALYSES
FROM UW-CIMSS INDICATES THAT THIS COULD BE THE RESULT OF ABOUT 20
KT OF LOW- TO MID-LEVEL SOUTHWESTERLY SHEAR IMPINGING ON THE
HURRICANE.  IN FACT...A 2308 UTC TRMM PASS SUGGESTED THAT THE
LOW-LEVEL CENTER COULD BE DECOUPLING TO THE SOUTH OF THE REMNANT
MID-LEVEL EYEWALL.  FINAL T-NUMBERS FROM TAFB AND SAB ARE 5.0 AND
4.5...RESPECTIVELY...AND THE 3-HOUR AVERAGE ADT IS DOWN TO 5.0. 
THE INITIAL INTENSITY IS THEREFORE LOWERED TO 90 KT ON THIS
ADVISORY.

IN ADDITION TO THE MID-LEVEL SHEAR...THE DEEP-LAYERED SHEAR IS
EXPECTED TO INCREASE WITHIN 24 HOURS OR SO.  THEREFORE...GRADUAL
WEAKENING IS ANTICIPATED OVER THE NEXT COUPLE OF DAYS.  BY ABOUT
DAY 3...THE VERTICAL SHEAR IS EXPECTED TO INCREASE SUBSTANTIALLY
ABOVE 30 KT AND THE SSTS WILL BE MARGINALLY WARM...SO QUICKER
WEAKENING SHOULD OCCUR AT THAT TIME.  THE OFFICIAL FORECAST IS A
LITTLE LOWER THAN THE INTENSITY CONSENSUS AFTER ABOUT 36 HOURS
SINCE THE GFDL AND HWRF APPEAR UNREALISTICALLY STRONG DURING THE
HIGH SHEAR.  ALTHOUGH THE NHC FORECAST STILL KEEPS FRED AS A
DEPRESSION AT DAY 5...IT IS ENTIRELY FEASIBLE THAT IT COULD BE A
REMNANT LOW BY THEN.

THE INITIAL MOTION ESTIMATE OF 320/9 MAY BE A LITTLE FAST IF THE
LOW- AND MID-LEVEL CIRCULATIONS ARE IN FACT BECOMING DECOUPLED. 
FRED IS EXPECTED TO TURN TOWARD THE NORTH OVER THE NEXT 24-36 HOURS
AS IT IS STEERED BETWEEN A MID-LEVEL ANTICYCLONE OVER THE CAPE
VERDE ISLANDS AND A TROUGH LOCATED TO ITS NORTHWEST.  BY 48 HOURS...
FRED IS FORECAST TO TURN TOWARD THE NORTHEAST AS THE AFOREMENTIONED
TROUGH MOVES EAST AND THE STEERING FLOW BECOMES SOUTHWESTERLY. 
FRED SHOULD THEN BECOME A SHALLOWER SYSTEM AFTER 72 HOURS AS THE
VERTICAL SHEAR INCREASES...AND AS A RESULT SHOULD TURN TOWARD THE
NORTH-NORTHWEST THEN WEST-NORTHWEST BY DAY 5 UNDER THE INFLUENCE OF
THE LOW-LEVEL TRADE WINDS.  THE OFFICIAL FORECAST DISCOUNTS THE
GFDL...HWRF...AND NOGAPS...WHICH ALL MAINTAIN FRED AS A DEEP SYSTEM
AND ARE NORTHERN OUTLIERS FROM THE REST OF THE GUIDANCE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      10/0300Z 15.3N  33.7W    90 KT
 12HR VT     10/1200Z 16.2N  34.4W    85 KT
 24HR VT     11/0000Z 17.1N  34.8W    80 KT
 36HR VT     11/1200Z 17.8N  34.7W    70 KT
 48HR VT     12/0000Z 18.4N  34.2W    60 KT
 72HR VT     13/0000Z 19.5N  33.5W    45 KT
 96HR VT     14/0000Z 22.0N  35.0W    35 KT
120HR VT     15/0000Z 23.5N  38.0W    25 KT
 
$$
FORECASTER BERG
 
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