Subtropical Depression TEN

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SUBTROPICAL DEPRESSION TEN DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL102007
1100 AM EDT FRI SEP 21 2007
 
CONVECTION ASSOCIATED WITH THE NON-TROPICAL LOW IN THE GULF HAS
GRADUALLY BECOME BETTER ORGANIZED SINCE YESTERDAY...WITH A
WELL-DEFINED BAND IN THE EASTERN SEMICIRCLE AND INTERMITTENT
CONVECTION CLOSER TO THE CENTER.  ALTHOUGH THE AMOUNT OF CONVECTION
PRESENT PROBABLY STRAINS THE DEFINITION A BIT...BECAUSE OF THE
POTENTIAL FOR ADDITIONAL DEVELOPMENT RIGHT ALONG THE COASTLINE...
ADVISORIES ARE BEING INITIATED ON SUBTROPICAL DEPRESSION TEN.  AN
AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT FIXED A SMALL
CIRCULATION CENTER A SHORT DISTANCE OFFSHORE OF APALACHICOLA...BUT
BUOY OBSERVATIONS SUGGEST THAT A LARGER-SCALE CENTER MAY BE FARTHER
SOUTH.  THE ILL-DEFINED NATURE OF THE SURFACE CIRCULATION...AS WELL
AS THE LINGERING UPPER-LOW ALOFT...PROVIDE THE RATIONALE FOR A
SUBTROPICAL CLASSIFICATION.

THE INITIAL MOTION ESTIMATE IS 325/7.  A MID-LEVEL RIDGE OF HIGH
PRESSURE STRETCHING FROM TEXAS NORTHEASTWARD IS EXPECTED TO TURN THE
DEPRESSION TO THE WEST-NORTHWEST ON A TRACK NEARLY PARALLEL TO THE
COASTLINE.   MODEL GUIDANCE IS IN GOOD AGREEMENT AND THE OFFICIAL
FORECAST FOLLOWS THE DYNAMICAL MODEL CONSENSUS.  BECAUSE THE
FORECAST TRACK IS NEARLY PARALLEL TO THE COASTLINE...A LANDFALL
LOCATION IS DIFFICULT TO PINPOINT...BUT IN ANY EVENT THE CENTER OF A
SUBTROPICAL CYCLONE IS RELATIVELY UNIMPORTANT.  MOST OF THE WEATHER
ASSOCIATED WITH THE SYSTEM IS WELL-DISPLACED FROM THE CENTER.

THE UPPER-LOW IS FRAGMENTING...WITH THE MAIN ENERGY SLIDING
SOUTHWEST OF THE DEPRESSION.  THIS WILL LEAVE THE DEPRESSION UNDER
LIGHT SOUTHEASTERLY FLOW OVER THE NEXT DAY OR SO.  THE FLOW OF
RELATIVELY COOL CONTINENTAL AIR INTO THE GULF AHEAD OF THE
SYSTEM...AS WELL AS ITS POOR ORGANIZATION...SHOULD PREVENT
EXCESSIVE DEVELOPMENT.  THE TROPICAL INTENSITY MODELS ALL SHOW
DEVELOPMENT TO A MID-RANGE TROPICAL STORM...WHILE THE GLOBAL
MODELS...WHICH MIGHT BE MORE APPROPRIATE TO THIS SITUATION...
FORECAST LITTLE STRENGTHENING.  THE OFFICIAL FORECAST REPRESENTS A
COMPROMISE AMONG THESE SOLUTIONS.  


FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/1500Z 29.2N  85.5W    30 KT
 12HR VT     22/0000Z 29.7N  86.6W    35 KT
 24HR VT     22/1200Z 30.1N  88.1W    40 KT
 36HR VT     23/0000Z 30.6N  90.3W    40 KT...INLAND
 48HR VT     23/1200Z 31.5N  93.0W    30 KT...INLAND
 72HR VT     24/1200Z...DISSIPATED
 
$$
FORECASTER FRANKLIN
 
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