Tropical Storm FRANCES

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TROPICAL STORM FRANCES DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT THU AUG 26 2004
 
THE CLOUD PATTERN IS BETTER ORGANIZED WITH A WELL-DEFINED CURVED
CLOUD BAND...DEEP CONVECTION NEAR THE CENTER AND GOOD OUTFLOW. IN
FACT...THERE WERE SOME INDICATIONS THAT A BANDING-TYPE EYE WAS
TRYING TO FORM IN EARLIER IMAGES. INITIAL INTENSITY HAS BEEN
INCREASED TO 50 KNOTS BUT IF THE FORMATION OF THE EYE MATERIALIZES
...WINDS COULD BE HIGHER THAN CURRENTLY ESTIMATED. BECAUSE THE
SHEAR IS LOW AND THE OCEAN IS WARM STRENGTHENING IS INDICATED. THIS
FORECAST IS IN AGREEMENT WITH THE GFDL AND SHIPS MODELS WHICH BRING
FRANCES TO NEAR 95 KNOTS. LATER IN THE PERIOD...A TURN OF THE
CYCLONE TO THE NORTHWEST MORE THAN INDICATED IN THE FORECAST COULD
BRING FRANCES TO A LESS FAVORABLE UPPER-LEVEL WIND ENVIRONMENT.   

FRANCES IS MOVING TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 15
KNOTS. GLOBAL MODELS CONTINUE TO FORECAST A MID-LEVEL TROUGH OVER
THE CENTRAL ATLANTIC. IN THE SHORT TERM...THIS FEATURE WILL LIKELY
ERODE THE SUBTROPICAL RIDGE FORCING FRANCES TO MOVE TOWARD THE
WEST-NORTHWEST AND NORTHWEST WITH A DECREASE IN FORWARD SPEED.
THEREAFTER...ONCE THE TROUGH MOVES OUT OR WEAKENS...MODELS ARE 
UNANIMOUSLY REDEVELOPING THE SUBTROPICAL RIDGE TO THE NORTH OF
FRANCES. THIS WILL LIKELY RESULT ON A TRACK BACK TO WEST-NORTHWEST
OR EVEN TOWARD THE WEST DEPENDING OF THE INTENSITY OF THE RIDGE.
BOTH THE GFS AND THE CANADIAN GLOBAL MODELS DEVELOP A STRONGER
RIDGE AND CONSEQUENTLY MOVE THE CYCLONE MORE TO THE WEST NEAR OR
OVER THE NORTHERN LEEWARD ISLANDS. THE UK AND THE NOGAPS DEVELOP A
WEAKER RIDGE ALLOWING THE CYCLONE TO MOVE WELL-NORTH OF THE LEEWARD
ISLANDS. THE OFFICIAL FORECAST IS IN BETWEEN THESE TWO OPTIONS. IT
IS SIGNIFICANT THAT EACH NEW RUN OF THE GLOBAL MODELS HAS A
FORECAST TRACK FARTHER TO WEST...SO IF THIS TREND CONTINUES...THERE
WILL BE INTERESTING DAYS AHEAD.       

FORECASTER AVILA
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0900Z 12.6N  43.7W    50 KT
 12HR VT     26/1800Z 13.3N  45.8W    65 KT
 24HR VT     27/0600Z 14.5N  48.0W    70 KT
 36HR VT     27/1800Z 16.0N  50.0W    80 KT
 48HR VT     28/0600Z 17.0N  51.5W    90 KT
 72HR VT     29/0600Z 18.5N  53.0W    90 KT
 96HR VT     30/0600Z 19.5N  55.0W    90 KT
120HR VT     31/0600Z 20.9N  59.0W    90 KT
 
 
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