Tropical Storm FRED

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TROPICAL STORM FRED DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072009
500 PM AST TUE SEP 08 2009
 
HIGH-RESOLUTION METEOSAT VISIBLE IMAGERY SHOW THAT FRED REMAINS A
WELL-ORGANIZED TROPICAL CYCLONE WITH PROMINENT BANDING AND
EXPANDING OUTFLOW IN ALL QUADRANTS.  THE BIGGEST CHANGE DURING THE
PAST SEVERAL HOURS IS THAT A CENTRAL DENSE OVERCAST FEATURE HAS
FORMED NEAR THE CENTER.  A 1514Z AMSR-E MICROWAVE PASS ALSO SHOWS
THE BEGINNING STAGES OF AN EYEWALL.  ALTHOUGH DVORAK INTENSITY
ESTIMATES ARE UNCHANGED...THE IMPROVED STRUCTURE ON MICROWAVE
IMAGES SUGGESTS SOME STRENGTHENING HAS OCCURRED AND THE INITIAL
INTENSITY IS RAISED TO 60 KT.  

THE INTENSITY FORECAST IS A BIT TRICKY THIS AFTERNOON WITH SOME
CONFLICTING SIGNALS PRESENT. THE AFOREMENTIONED AMSR-E PASS SHOWED
A CLOSED RING PATTERN ON THE 37 GHZ CHANNEL...WHICH HAS BEEN A
HARBINGER OF RAPID INTENSIFICATION BEFORE.  IN COMBINATION WITH
WARM WATERS AND LOW SHEAR...IT IS TEMPTING TO FORECAST SIGNIFICANT
STRENGTHENING. HOWEVER...SOME GLOBAL MODELS ARE SHOWING THE SHEAR
INCREASING BY TOMORROW...WHICH COULD LIMIT FURTHER DEVELOPMENT. 
THERE IS A FAIR AMOUNT OF SPREAD IN THE INTENSITY GUIDANCE THIS
AFTERNOON WITH THE SHIPS/LGEM SHOWING ONLY A LITTLE MORE
INTENSIFICATION WHILE THE HWRF/GFDL STILL HAVE FRED REACHING
CATEGORY 2 STATUS.  THE NHC FORECAST WILL BE CLOSER TO THE
DYNAMICAL MODELS...SHOWING A PEAK INTENSITY IN ABOUT 24-36 HRS
BEFORE THE SHEAR INCREASES.  THEREAFTER...COOLER WATERS...STRONGER
SHEAR AND DRIER AIR SHOULD SIGNIFICANTLY WEAKEN FRED...AND IT WOULD
NOT BE SURPRISING IF FRED WAS ONLY A REMNANT LOW BY DAY 5.
 
THE INITIAL MOTION IS ABOUT 280/12.  A NARROW RIDGE OVER THE EASTERN
ATLANTIC IS CURRENTLY THE PRIMARY FEATURE STEERING FRED.  HOWEVER A
MID- TO UPPER-LEVEL TROUGH IS EXPECTED TO ERODE THE RIDGE...CAUSING
THE TRACK OF THE STORM TO GRADUALLY BEND FROM WEST-NORTHWEST...
NORTHWEST...THEN TO THE NORTH BY DAY THREE.  MODEL GUIDANCE IS IN
BETTER AGREEMENT ON THIS SCENARIO THAN THIS MORNING.  AFTER 72
HR...GLOBAL MODELS ARE GENERALLY SUGGESTING MORE OF A MOTION TOWARD
THE NORTHEAST THAN EARLIER...PERHAPS DUE TO THEIR DEPICTION OF A
STRONGER CYCLONE INTERACTING MORE WITH THE TROUGH.  THE OFFICIAL
FORECAST HAS BEEN SHIFTED TO THE NORTHEAST IN THE LONGER-RANGE...
BUT IS STILL SOUTH OF THE MODEL CONSENSUS.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/2100Z 12.1N  29.8W    60 KT
 12HR VT     09/0600Z 12.8N  31.3W    70 KT
 24HR VT     09/1800Z 13.9N  32.8W    80 KT
 36HR VT     10/0600Z 15.2N  33.9W    80 KT
 48HR VT     10/1800Z 16.4N  34.4W    70 KT
 72HR VT     11/1800Z 18.0N  34.0W    55 KT
 96HR VT     12/1800Z 19.5N  33.5W    45 KT
120HR VT     13/1800Z 22.0N  34.0W    30 KT
 
$$
FORECASTER BLAKE
 
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