Tropical Storm FRED

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TROPICAL STORM FRED DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072009
500 AM AST TUE SEP 08 2009

FRED IS GRADUALLY BECOMING BETTER ORGANIZED IN SATELLITE IMAGES. 
THE STORM IS EXHIBITING A WELL-DEFINED CURVED BAND FEATURE WRAPPING
AROUND A DEVELOPING CENTRAL DENSE OVERCAST.  BASED ON THE
BANDING...DVORAK DATA T-NUMBERS ARE AT LEAST 3.0.  THE CURRENT
INTENSITY ESTIMATE IS 45 KT FROM BOTH TAFB MIAMI AND SAB
WASHINGTON...AND THE ADVISORY INTENSITY IS ALSO SET AT 45 KT. 
CIRRUS MOTIONS INDICATE STRONG UPPER-LEVEL OUTFLOW IN ALL QUADRANTS
OF THE SYSTEM.  VERTICAL SHEAR IS EXPECTED TO REMAIN WEAK FOR THE
NEXT DAY OR TWO...SO ADDITIONAL INTENSIFICATION SEEMS LIKELY.      
GIVEN THE CURRENT ORGANIZATION AND FAVORABLE SHORT-TERM
ENVIRONMENT...FRED CERTAINLY HAS THE POTENTIAL TO BECOME A
HURRICANE WITHIN THE NEXT 36 HOURS.  THE OFFICIAL INTENSITY
FORECAST IS QUITE CLOSE TO THE SHIPS AND LGEM GUIDANCE THROUGH DAY
3.  BEYOND THAT TIME...A LARGE UPPER-TROPOSPHERIC TROUGH OVER THE
CENTRAL ATLANTIC SHOULD PRODUCE INCREASING SOUTHWESTERLY SHEAR OVER
FRED.  THAT...ALONG WITH A SLIGHTLY COOLER OCEAN...WILL PROBABLY
INDUCE WEAKENING.  THE OFFICIAL FORECAST FOR DAYS 4 AND 5 DOES NOT
WEAKEN THE CYCLONE QUITE AS FAST AS INDICATED BY SOME OF THE
GUIDANCE.

LATEST CENTER FIXES INDICATE A CONTINUED WESTWARD MOTION AT AROUND
275/13.  THE NARROW MID-TROPOSPHERIC RIDGE CURRENTLY TO THE NORTH
OF FRED IS FORECAST BY THE GLOBAL MODELS TO BECOME ERODED OVER THE
NEXT COUPLE OF DAYS BY A MID-TO UPPER-LEVEL LOW CURRENTLY SEEN IN
WATER VAPOR IMAGES NEAR 28N AND 40W.  THIS EVOLUTION SHOULD CAUSE
FRED TO GRADUALLY TURN NORTHWESTWARD AND NORTHWARD OVER THE EASTERN
ATLANTIC.  NEAR THE END OF THE FORECAST PERIOD...THE GLOBAL MODELS
SHOW WEAK RIDGING DEVLOPING AGAIN TO THE NORTH OF THE TROPICAL
CYCLONE.  IN RESPONSE TO THIS...SOME OF THE TRACK MODELS TURN THE
SYSTEM TOWARD THE NORTHWEST BY DAY 5 WITH A VERY SLOW FORWARD
SPEED.  THE OFFICIAL FORECAST SHOWS A SLOWING OF THE FORWARD SPEED
THROUGH THE PERIOD AND HINTS AT A SLIGHT TURN TO THE LEFT AT 96-120
HOURS.  THE GFDL AND HWRF MODELS TAKE FRED MUCH FARTHER NORTH IN 5
DAYS...BUT ARE BEING TREATED AS OUTLIERS FOR THE TIME BEING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 11.8N  27.3W    45 KT
 12HR VT     08/1800Z 12.1N  29.0W    55 KT
 24HR VT     09/0600Z 13.0N  30.9W    60 KT
 36HR VT     09/1800Z 13.9N  32.5W    65 KT
 48HR VT     10/0600Z 15.1N  33.5W    65 KT
 72HR VT     11/0600Z 17.5N  34.0W    60 KT
 96HR VT     12/0600Z 19.0N  34.0W    55 KT
120HR VT     13/0600Z 20.5N  34.5W    55 KT
 
$$
FORECASTER PASCH
 
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