Tropical Storm FLORENCE

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TROPICAL STORM FLORENCE DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062006
500 PM EDT TUE SEP 05 2006
 
THE LOW-LEVEL CIRCULATION CENTER...AS WELL AS CONVECTIVE BANDING
FEATURES HAS BECOME BETTER DEFINED IN VISIBLE SATELLITE IMAGERY.
THUNDERSTORM ACTIVITY HAS ALSO BEGUN TO DEVELOP IN THE INNER CORE
REGION. GIVEN THE OVERALL IMPROVEMENT IN THE CONVECTIVE STRUCTURE
OF FLORENCE...PLUS A 05/1641Z UW-CIMSS AMSU ESTIMATE OF 1003 MB AND
42 KT...THE INITIAL INTENSITY HAS BEEN INCREASED TO 40 KT. 
 
THE INITIAL MOTION ESTIMATE IS 290/10. ALL OF THE GLOBAL AND
REGIONAL MODELS CONTINUE TO AGREE ON A GENERAL WEST-NORTHWESTWARD
MOTION THROUGH 96 HOURS...WITH A TURN TOWARD THE NORTHWEST INTO A
DEVELOPING WEAKNESS IN THE SUBTROPICAL RIDGE AFTER THAT. THE MODELS
HAVE BEEN VERY PERSISTENT IN DEVELOPING AN EVENTUAL BREAK IN THE
RIDGE AXIS BETWEEN 65W-75W FOR THE PAST SEVERAL RUNS. HOWEVER
...EACH RUN HAS SHIFTED THE TRACK A LITTLE FARTHER TO THE WEST.
GIVEN THAT THE MID- TO UPPER-LEVEL FLOW IS FORECAST TO BE
WEST-SOUTHWESTERLY NORTH OF THE RIDGE AXIS...AND THAT A LARGE
MID-LATITUDE TROUGH IS EXPECTED TO DIG INTO THE CENTRAL U.S. BY DAY
5...THE MODELS MAY BE OVERDOING THE AMOUNT OF SHORTWAVE ENERGY
FORECAST TO GENERATE THE WEAKNESS IN THE RIDGE. THE OFFICIAL
FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS TRACK...AND
REMAINS A LITTLE SOUTH OF THE MODEL CONSENSUS AND ALONG THE
SOUTHERN PORTION OF THE NHC MODEL GUIDANCE ENVELOPE.

ALTHOUGH FLORENCE CONTINUES TO GET BETTER ORGANIZED...IT REMAINS AN
UNUSUALLY LARGE ATLANTIC TROPICAL STORM...AND LARGE CYCLONES TEND
TO TAKE LONGER TO DEVELOP AND INTENSIFY THAN SMALLER ONES DO. AS A
RESULT...ONLY MODEST INTENSIFICATION IS FORECAST FOR THE NEXT 48
HOURS OR SO...WITH A FASTER RATE OF STRENGTHENING INDICATED AFTER
THAT AS FLORENCE MOVES OVER 29-29.5C SSTS AND BENEATH DECREASING
VERTICAL SHEAR. IF FLORENCE MOVES UNDERNEATH THE CENTER OF A 200 MB
ANTICYCLONE LIKE THE NOGAPS...UKMET...AND ECMWF MODELS ARE
SUGGESTING...THEN STRENGTHENING INTO A MAJOR HURRICANE LIKE THE
GFDL AND FSU SUPERENSEMBLE MODELS ARE FORECASTING WILL BE POSSIBLE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2100Z 17.4N  48.5W    40 KT
 12HR VT     06/0600Z 18.0N  49.9W    45 KT
 24HR VT     06/1800Z 18.8N  51.9W    50 KT
 36HR VT     07/0600Z 19.7N  54.0W    55 KT
 48HR VT     07/1800Z 20.6N  56.5W    60 KT
 72HR VT     08/1800Z 22.3N  61.1W    70 KT
 96HR VT     09/1800Z 24.3N  65.7W    80 KT
120HR VT     10/1800Z 27.0N  69.0W    90 KT
 
$$
FORECASTER STEWART
 
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