237
WTNT41 KNHC 041457
TCDAT1
TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009
1000 AM EST WED NOV 04 2009
THE AREA OF LOW PRESSURE IN THE SOUTHWESTERN CARIBBEAN SEA HAS
DEVELOPED ENOUGH ORGANIZED THUNDERSTORM ACTIVITY TO NOW BE
CONSIDERED A TROPICAL DEPRESSION. SATELLITE IMAGES SHOW THAT A NEW
BURST OF THUNDERSTORMS IS OCCURRING NEAR THE CENTER WITH BANDING
FEATURES BECOMING MORE DISTINGUISHED. TAFB/SAB DVORAK
CLASSIFICATIONS WERE 2.0...30 KT...AT 1200 UTC...AND THAT INTENSITY
WILL BE USED AS THE INITIAL WIND SPEED. IT WOULD NOT BE
SURPRISING...HOWEVER...IF THIS SYSTEM WERE ALREADY A TROPICAL STORM
DUE TO THE IMPROVING SATELLITE PRESENTATION. THE AIR FORCE RESERVE
WILL BE IN THE AREA THIS AFTERNOON TO GIVE A BETTER ESTIMATE OF THE
WINDS.
THE INITIAL MOTION USED FOR THIS ADVISORY IS 315/7...THOUGH IT IS
UNCERTAIN WHETHER THIS IS TRULY REPRESENTATIVE DUE TO THE CENTER
REFORMATION THAT APPEARED TO OCCUR OVERNIGHT. STEERING CURRENTS ARE
EXPECTED TO BE FAIRLY LIGHT DURING THE NEXT SEVERAL DAYS AS THE
DEPRESSION IS CAUGHT BETWEEN A WEAK MID-LEVEL HIGH OVER THE
NORTH-CENTRAL CARIBBEAN SEA AND A TROUGH OVER THE SOUTHWESTERN GULF
OF MEXICO. ALTHOUGH THERE IS GENERAL AGREEMENT IN THE LARGE-SCALE
PATTERN...THE MODELS ARE SHOWING A LARGE AMOUNT OF DIVERGENCE ON
THE EXPECTED PATH OF THE DEPRESSION. MOST OF THE GUIDANCE SUGGEST
THE SYSTEM WILL MOVE TO THE NORTHWEST THEN NORTH AROUND THE
SOUTHWESTERN PERIPHERY OF THE CARIBBEAN RIDGE. HOWEVER...SOME OF
THE RELIABLE GUIDANCE...SUCH AS THE ECMWF AND UKMET...SHOW THE
SYSTEM MOVING CONSIDERABLY SLOWER WITH ONLY A NORTHWARD DRIFT.
GIVEN THE UNCERTAINTY...THE NHC FORECAST IS NEAR BUT SLIGHTLY TO
THE RIGHT OF THE MODEL CONSENSUS.
ALTHOUGH THE DEPRESSION IS CURRENTLY IN A LIGHT SHEAR AND WARM WATER
ENVIRONMENT...ITS PROXIMITY TO LAND AND UNCERTAIN TRACK FORECAST
LEADS TO A COMPLEX INTENSITY FORECAST. THE GFDL...ONE OF THE ONLY
MODELS THAT KEEPS THE SYSTEM OFFSHORE...MAKES THE SYSTEM A
HURRICANE IN A FEW DAYS. HOWEVER...NEITHER THE SHIPS NOR THE LGEM
MODELS SHOW MUCH INTENSIFICATION AT ALL. THESE MODELS SEEM TO BE A
LITTLE UNDERDONE...AND THE NHC FORECAST WILL BE ON THE HIGHER SIDE
OF THE GUIDANCE ENVELOPE...THOUGH NOT AS HIGH AS THE GFDL.
FORECAST POSITIONS AND MAX WINDS
INITIAL 04/1500Z 11.6N 82.0W 30 KT
12HR VT 05/0000Z 11.9N 82.3W 45 KT
24HR VT 05/1200Z 12.5N 83.0W 50 KT
36HR VT 06/0000Z 13.0N 83.5W 50 KT
48HR VT 06/1200Z 13.5N 84.0W 35 KT...INLAND
72HR VT 07/1200Z 14.5N 84.5W 25 KT...INLAND
96HR VT 08/1200Z 15.5N 85.0W 25 KT...INLAND
120HR VT 09/1200Z 18.0N 85.5W 35 KT...OVER WATER
FORECASTER BLAKE/FRANKLIN
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