[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 102038
TCDAT2
HURRICANE FRED DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072009
500 PM AST THU SEP 10 2009

THE EYE HAS BEEN INTERMITTENT ON VISIBLE IMAGES AND THE CLOUD
PATTERN IS BECOMING ELONGATED DUE TO INCREASING SOUTHWESTERLY SHEAR.
CONVECTION IS STILL DEEP NEAR THE CENTER AND THE OUTFLOW IS MOSTLY
TO THE NORTH AND NORTHEAST. SATELLITE INTENSITY ESTIMATES INDICATE
THAT THE INITIAL INTENSITY HAS DECREASED TO 80 KNOTS BASED ON
LOWER DVORAK T-NUMBERS. MOST OF THE GLOBAL MODELS SHOW MASSIVE
UPPER-LEVEL SOUTHWESTERLY WINDS AFFECTING THE CYCLONE VERY
SOON. THESE WINDS ARE FUELED BY A STRONGER THAN NORMAL AND
PERSISTENT MID-OCEANIC UPPER-LEVEL TROUGH TO THE WEST OF FRED.
THIS UPPER-LEVEL PATTERN FAVORS WEAKENING...AND THIS PROCESS SHOULD
ACCELERATE DURING THE NEXT 24 HOURS OR SO. IN ABOUT 4 DAYS...FRED
SHOULD BECOME A REMNANT LOW.

FRED IS MOVING TOWARD THE NORTH AT ABOUT 4 TO 6 KNOTS...BUT SOON
STEERING CURRENTS ARE FORECAST TO COLLAPSE AND THE HURRICANE SHOULD
BECOME STATIONARY OR BEGIN TO MEANDER AROUND 19 DEGREES NORTH
DURING THE 2 OR 3 DAYS. THEREAFTER...GLOBAL MODELS DEVELOP A
SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE...FORCING FRED OR ITS
REMNANTS TO MOVE TOWARD THE WEST-NORTHWEST. BY THEN...FRED WILL
PROBABLY BE A VERY WEAK SHALLOW CYCLONE STEERED BY THE LOW-LEVEL
TRADE WINDS. IN IS INTERESTING TO NOTE THAT MOST OF THE GUIDANCE
HAS CHANGED...AND NOW UNANIMOUSLY BEND THE TRACK WESTWARD. A COUPLE
OF DAYS AGO...SOME OF THE MOST RELIABLE MODELS INCLUDING THE ECMWF
TURNED FRED TOWARD THE NORTH-NORTHEAST TOWARD AFRICA OR EUROPE.

FORECAST POSITIONS AND MAX WINDS

INITIAL      10/2100Z 17.3N  35.1W    80 KT
 12HR VT     11/0600Z 17.9N  35.2W    70 KT
 24HR VT     11/1800Z 18.1N  35.2W    60 KT
 36HR VT     12/0600Z 18.2N  35.2W    50 KT
 48HR VT     12/1800Z 18.3N  35.2W    40 KT
 72HR VT     13/1800Z 19.5N  36.0W    30 KT
 96HR VT     14/1800Z 21.5N  39.5W    25 KT...REMNANT LOW
120HR VT     15/1800Z 22.5N  44.0W    20 KT...REMNANT LOW

$$
FORECASTER AVILA

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