Tropical Storm FIONA

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TROPICAL STORM FIONA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 PM AST TUE AUG 31 2010

THE METEO FRANCE GUADELOUPE-MARTINIQUE RADAR MOSAIC WAS VERY HELPFUL
IN IDENTIFYING THE CIRCULATION CENTER OF FIONA.  DEEP CONVECTION
HAS BEEN PERSISTENT NEAR THE CENTER...BUT THE CLOUD PATTERN IS A
RATHER SHAPELESS BLOB...AND APPEARS TO BE ELONGATED ALONG AN AXIS
SOUTHEAST TO NORTHWEST.  THE DVORAK INTENSITY ESTIMATES REMAIN AT
30 KT FROM BOTH TAFB AND SAB...BUT THE INITIAL INTENSITY WILL
REMAIN AT 35 KT BASED ON THE PERSISTENT DEEP CONVECTION TO THE
NORTH OF THE CENTER WHERE THE EARLIER AIRCRAFT RECONNAISSANCE
RECORDED FLIGHT-LEVEL WINDS OF 41 KT.  NORTHEASTERLY SHEAR
ASSOCIATED WITH THE SOUTHEAST OUTFLOW CHANNEL OF EARL IS EXPECTED
TO IMPINGE ON THE WESTERN PORTION OF THE CYCLONE IN 36 HOURS.  THE
SHIPS MODEL AS WELL AS THE GLOBAL MODELS ALL SUGGEST THAT THE SHEAR
WILL SIGNIFICANTLY INCREASE OVER THE CYCLONE THROUGH DAY 3...
CAUSING DISSIPATION BY DAY 4.  THERE IS SOMEWHAT OF A CHANCE...
HOWEVER...OF MINIMAL STRENGTHENING PRIOR TO THE INCREASING
SHEAR DURING THE EARLY PORTION OF THE FORECAST. 
 
THE INITIAL MOTION IS SIMILAR TO THE PREVIOUS ADVISORY
ESTIMATE...BUT A LITTLE SLOWER...290/17 KT.  LARGE-SCALE MODELS
INDICATE THAT FIONA WILL TURN NORTHWESTWARD ALONG THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT 24 HOURS.
THROUGH THE REMAINING FORECAST PERIOD...THE CYCLONE SHOULD TURN
NORTHWARD WITHIN A STIFF SOUTHERLY FLOW BETWEEN THE RIDGE EXTENDING
OVER BERMUDA AND HURRICANE EARL TO THE NORTHWEST.  THE OFFICIAL
FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE...WITH ONLY A SLIGHT
ADJUSTMENT TO THE LEFT...AND IS BASED ON THE MULTI-MODEL TVCN
CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0300Z 16.9N  59.4W    35 KT
 12HR VT     01/1200Z 18.7N  62.0W    40 KT
 24HR VT     02/0000Z 21.2N  64.7W    40 KT
 36HR VT     02/1200Z 24.4N  66.5W    40 KT
 48HR VT     03/0000Z 27.8N  67.6W    35 KT
 72HR VT     04/0000Z 35.0N  66.0W    30 KT
 96HR VT     05/0000Z...DISSIPATED
 
$$
FORECASTER ROBERTS/PASCH
 
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