Tropical Storm FLORENCE

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TROPICAL STORM FLORENCE DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062006
500 AM EDT FRI SEP 08 2006

AS DEPICTED IN INFRARED SATELLITE IMAGERY...FLORENCE HAS A VERY
LARGE CIRCULATION BUT CONTINUES TO STRUGGLE IN ORGANIZATION.  EVEN
THOUGH DVORAK ESTIMATES REMAIN AT 35 KNOTS FROM BOTH TAFB AND
SAB...THE INITIAL INTENSITY IS KEPT AT 45 KT WITH THE EXPECTATION
THAT SOME STRENGTHENING AND CONSOLIDATION OF THE CLOUD STRUCTURE
WILL SOON COMMENCE.  

WATER VAPOR IMAGERY SHOWS FLORENCE SANDWICHED BETWEEN AN UPPER-LEVEL
LOW JUST TO ITS SOUTHWEST AND A RATHER STRONG RIDGE TO ITS NORTH.
THESE FEATURES HAVE HELPED INCREASE THE FORWARD MOTION AND IT IS NOW
ESTIMATED TO BE 300/14.  A VERY DEEP TROUGH IS NOW DIGGING SOUTHWARD
INTO THE CENTRAL GULF OF MEXICO...AND TAKING A LOOK AT THE
INITIALIZATION OF SOME OF THE GLOBAL MODELS...PARTICULARLY THE
GFS...THE TROUGH MAY BE UNDERESTIMATED.  WITH THAT SAID...THE MODEL
GUIDANCE IS IN CLOSE AGREEMENT IN THE FIRST 72 HOURS...GRADUALLY
SLOWING FLORENCE AS IT APPROACHES THE WESTERN PERIPHERY OF THE
RIDGE AND TURNING THE CYCLONE TO NORTH AND APPROACH BERMUDA.  ONCE
FLORENCE IS NORTH OF THE ISLAND THE MODELS DIFFER IN THE
ACCELERATION RATE AT DAYS 4 AND 5.  THE OFFICIAL TRACK FORECAST
STAYS IN LINE WITH THE MOTION REPRESENTED BY THE GFS...NOGAPS...
AND FSU SUPERENSEMBLE WITH FLORENCE STARTING TRANSITION TO AN
EXTRATROPICAL CYCLONE AROUND DAY 5.

ONCE AGAIN...THE INTENSITY FORECAST IS PROBLEMATIC. SINCE FLORENCE
IS SUCH A LARGE CIRCULATION...STRENGTHENING WILL TAKE LONGER TO
OCCUR.  THE OFFICIAL INTENSITY FORECAST IS A BLEND OF THE SHIPS AND
GFDL GUIDANCE.  FOR SOME UNKNOWN REASON...THE FSU SUPERENSEMBLE
SIGNIFICANTLY STRENGTHENS FLORENCE AFTER RECURVATURE OCCURS.  THIS
SOLUTION IS DISCOUNTED AS THE SHEAR IS EXPECTED TO INCREASE TO OVER
40 KNOTS AFTER 3 DAYS. 

THE BERMUDA WEATHER SERVICE WILL LIKELY ISSUE WATCHES OR WARNINGS
WITHIN THE NEXT 24 HOURS.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 22.1N  57.6W    45 KT
 12HR VT     08/1800Z 23.1N  59.5W    50 KT
 24HR VT     09/0600Z 24.4N  61.7W    55 KT
 36HR VT     09/1800Z 25.8N  63.6W    65 KT
 48HR VT     10/0600Z 27.4N  64.6W    75 KT
 72HR VT     11/0600Z 31.0N  65.0W    90 KT...NEAR BERMUDA
 96HR VT     12/0600Z 37.0N  62.0W    85 KT
120HR VT     13/0600Z 45.0N  53.0W    80 KT...BECOMING EXTRATROPICAL
 
$$
FORECASTER MAINELLI/BEVEN
 
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