Tropical Storm FLORENCE

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM FLORENCE DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062006
500 PM EDT WED SEP 06 2006
 
EVEN AS FLORENCE SHOWS SIGNS OF BECOMING BETTER ORGANIZED...THE
CENTER REMAINS MADDENINGLY DIFFICULT TO TRACK. THE WELL-DEFINED
LOW-CLOUD SWIRL HAS BEEN ROTATING NORTHWARD THIS AFTERNOON AROUND A
PRESUMED BUT INVISIBLE OVERALL SYSTEM CENTER TO ITS WEST. AN 18
HOUR AVERAGE GIVES 295/8 FOR THE ADVISORY MOTION. THERE HAS BEEN NO
CHANGE TO THE TRACK FORECAST REASONING...SO I'LL JUST PLAGIARIZE
THIS MORNING'S DISCUSSION. THE KEY SYNOPTIC FEATURE IN THE SHORT
TERM REMAINS THE UPPER LOW CENTERED A FEW HUNDRED MILES NORTHWEST
OF FLORENCE. THIS COULD IMPART MORE OF A NORTHWARD TRACK OVER THE
NEXT DAY OR SO...AS INDICATED BY THE GFDL MODEL...BUT THE REMAINING
GUIDANCE IS TIGHTLY CLUSTERED ON A CONTINUED WEST-NORTHWESTWARD
MOTION OVER THE NEXT THREE DAYS AS FLORENCE MOVES TO THE SOUTH OF
THE MID-LEVEL SUBTROPICAL RIDGE. NEAR THE END OF THE FORECAST
PERIOD...FLORENCE IS EXPECTED TO ROUND THE PERIPHERY OF THE RIDGE
IN ADVANCE OF A DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES.
MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON A NORTHWARD TURN
BY DAY 4. THE OFFICIAL FORECAST IS JUST AN UPDATE OF THE PREVIOUS
ADVISORY...AND IS CLOSE TO A CONSENSUS OF THE WELL-CLUSTERED
PRIMARY DYNAMICAL MODELS.  

THE MAJOR CHANGE IN ORGANIZATION TODAY IS THAT THE CONVECTION HAS
BEEN GRADUALLY MIGRATING CLOSER TO THE CENTER OF CIRCULATION.  OVER
THE PAST COUPLE OF HOURS CONVECTION HAS ALSO BEEN INCREASING OVER
THE NOW-OBSCURED CLOUD SWIRL...AND THIS MAY BE THE BEGINNING OF A
MORE SUBSTANTIAL INTENSIFICATION.  AS THE UPPER LOW MOVES
WESTWARD...SHEAR WILL CONTINUE TO DECREASE AND THE ENVIRONMENT
SHOULD BECOME MORE CONDUCIVE FOR DEVELOPMENT.  GLOBAL MODELS AGREE
ON DEVELOPING A LARGE ANTICYCLONE OVER FLORENCE IN THREE DAYS OR SO
AND THE OFFICIAL FORECAST FOLLOWS A BLEND OF THE SHIPS AND GFDL
GUIDANCE IN MAKING FLORENCE A MAJOR HURRICANE.  TOWARD THE END OF
THE FORECAST PERIOD...GUIDANCE IS ALSO IN GOOD AGREEMENT THAT
FLORENCE...ALREADY A LARGE CYCLONE...WILL GET EVEN LARGER.  
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/2100Z 19.0N  51.4W    45 KT
 12HR VT     07/0600Z 20.0N  53.0W    50 KT
 24HR VT     07/1800Z 21.5N  55.5W    60 KT
 36HR VT     08/0600Z 22.7N  58.2W    70 KT
 48HR VT     08/1800Z 23.7N  60.7W    80 KT
 72HR VT     09/1800Z 26.0N  65.0W    95 KT
 96HR VT     10/1800Z 29.0N  67.0W   100 KT
120HR VT     11/1800Z 32.5N  67.0W    95 KT
 
$$
FORECASTER FRANKLIN
 
NNNN