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#108540 (Received by flhurricane at: 10:31 PM 03.Sep.2006) TCDAT1 TROPICAL DEPRESSION SIX DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062006 1100 PM EDT SUN SEP 03 2006 THERE HAS BEEN ONLY A SLIGHT INCREASE IN THE APPARENT ORGANIZATION OF THE SYSTEM. BANDING FEATURES NEAR THE ESTIMATED CENTER ARE A LITTLE BETTER DEFINED...HOWEVER THE HIGH CLOUDS ARE BECOMING A LITTLE MORE ELONGATED TO THE NORTH AND UPPER-LEVEL OUTFLOW IS NOT WELL-ESTABLISHED OVER THE SOUTHWEST PART OF THE CYCLONE. DVORAK INTENSITY ESTIMATES ARE 30 KT...30 KT...AND 35 KT FROM TAFB...AFWA...AND SAB RESPECTIVELY. BECAUSE THE UNCERTAINTY IN CENTER LOCATION LEADS TO UNCERTAINTY IN SATELLITE-BASED INTENSITY ESTIMATION...THE WIND SPEED IS HELD AT 30 KT FOR THIS ADVISORY. SOME SOUTHWESTERLY SHEAR...ASSOCIATED WITH AN UPPER-TROPOSPHERIC TROUGH TO THE NORTHWEST OF THE DEPRESSION...COULD INHIBIT STRENGTHENING DURING THE NEXT COUPLE OF DAYS. HOWEVER THIS SHEAR IS NOT EXPECTED TO BECOME PROHIBITIVELY STRONG SO A GRADUAL INCREASE IN INTENSITY IS FORECAST. LATER IN THE FORECAST PERIOD...THE UPPER-LEVEL ENVIRONMENT IS PREDICTED TO BECOME MORE CONDUCIVE FOR STRENGTHENING. THE OFFICIAL INTENSITY FORECAST IS VERY SIMILAR TO THE SHIPS GUIDANCE IN THE LATTER PART OF THE PERIOD...BUT BELOW THE 1800 UTC GFDL GUIDANCE IN 4-5 DAYS. WE BELIEVE THAT THIS PARTICULAR RUN OF THE GFDL MODEL HAD A HIGH INTENSITY BIAS DUE TO PROBLEMS WITH THE OCEAN COUPLING. IT IS QUITE DIFFICULT TO LOCATE THE LOW-LEVEL CENTER AT THIS TIME BUT THE LATEST FIXES ARE ALL TO THE EAST OF PREVIOUS POSITION ESTIMATES. THEREFORE THE BEST TRACK HAS BEEN ADJUSTED A LITTLE TO THE RIGHT AND WITH A SLOWER FORWARD SPEED. MY INITIAL MOTION ESTIMATE IS AN UNCERTAIN 310/10. A WEAKNESS IN THE MID-LEVEL RIDGE NEAR 50W LONGITUDE SHOULD ALLOW THE CURRENT NORTHWESTWARD MOTION TO MORE OR LESS CONTINUE FOR THE NEXT DAY OR SO. THEREAFTER...THE GLOBAL MODELS SHOW A RIDGE BUILDING EASTWARD TO THE NORTH OF THE TROPICAL CYCLONE. THIS CHANGE IN THE STEERING PATTERN WOULD CAUSE THE TRACK TO BEND TOWARD THE LEFT IN 3-5 DAYS. THE OFFICIAL TRACK FORECAST IS CLOSE TO THE DYNAMICAL MODEL CONSENSUS AND ONLY SLIGHTLY TO THE LEFT OF THAT FROM THE PREVIOUS ADVISORY. IT SHOULD BE RECALLED THAT TRACK FORECAST ERRORS CAN BE SEVERAL HUNDRED MILES IN THE 5-DAY TIME FRAME. FORECAST POSITIONS AND MAX WINDS INITIAL 04/0300Z 14.8N 40.4W 30 KT 12HR VT 04/1200Z 15.9N 42.0W 35 KT 24HR VT 05/0000Z 17.0N 43.8W 40 KT 36HR VT 05/1200Z 18.0N 45.5W 45 KT 48HR VT 06/0000Z 18.9N 47.3W 50 KT 72HR VT 07/0000Z 20.5N 51.5W 55 KT 96HR VT 08/0000Z 21.5N 56.0W 65 KT 120HR VT 09/0000Z 22.5N 61.0W 75 KT $$ FORECASTER PASCH |