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| #52110 (Received by flhurricane at: 11:03 PM 16.Oct.2005) TCDAT4 TROPICAL DEPRESSION TWENTY-FOUR DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN OCT 16 2005 THE CONVECTIVE STRUCTURE OF THE DEPRESSION HAS CERTAINLY CHANGED DURING THE PAST 24 HOURS. WHILE OUTER BANDS HAVE DISSIPATED... SOME VERY DEEP CONVECTION HAS ERUPTED NEAR AND ESPECIALLY TO THE SOUTH OF THE CIRCULATION CENTER TONIGHT... ALTHOUGH THE CONVECTION HAS BEEN PERCOLATING RATHER THAN MAINTAINING CONSISTENCY NEAR THE CENTER. DVORAK INTENSITY ESTIMATES AT 00Z WERE T2.5/35 KT FROM TAFB AND SAB AND T2.0/30 KT FROM AFWA. WIND OBSERVATIONS FROM NOAA BUOY 42057 ABOUT 60 MILES WEST OF THE CENTER AND OUTSIDE OF THE CONVECTION HAVE BEEN NO STRONGER THAN 19 KT DURING THE EVENING... AND IT IS NOT CERTAIN THAT THE WINDS ARE TWICE THAT STRONG BENEATH THE DEEP CONVECTION. EVEN THOUGH THE ADVISORY INTENSITY IS HELD AT 30 KT... THE DEPRESSION APPEARS VERY CLOSE TO TROPICAL STORM STATUS AND WILL LIKELY REACH IT ON MONDAY MORNING. THE INITIAL MOTION REMAINS ALMOST NON-EXISTENT BUT IS ESTIMATED TO BE 275/2. THE VARIOUS DYNAMICAL MODELS AGREE ON A GENERAL WESTWARD TRACK FOR THE NEXT 2-3 DAYS WITH PERHAPS A SLIGHT INCREASE IN FORWARD SPEED. THE WESTWARD TREND CONTINUES IN THE 18Z RUNS OF THE GFS AND GFDL WHICH NOW FORECAST THE TROPICAL CYCLONE TO REACH THE YUCATAN PENINSULA IN ABOUT FOUR DAYS. THE LAST FEW GFS RUNS HAVE BEEN HANGING ON TO PROGRESSIVELY MORE MID-LEVEL RIDGING FOR THE NEXT THREE DAYS OR SO OVER THE WESTERN GULF OF MEXICO... AND SLIGHTLY MORE ZONAL FLOW OVER THE SOUTHEASTERN UNITED STATES ON DAYS 4-5. THE NEW GFS AND GFDL SOLUTIONS ARE NOW MUCH CLOSER TO THE NOGAPS... WHICH IS STILL ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE BUT HAS NUDGED A LITTLE BACK TO THE NORTH. THE FORECAST PATTERN NOW ANTICIPATED BY MOST OF THE MODELS WOULD DELAY A TURN OF THE TROPICAL CYCLONE NORTHWARD TO VERY LATE IN THE FIVE DAY FORECAST PERIOD. THE NEW OFFICIAL FORECAST IS AGAIN ADJUSTED SOUTHWESTWARD TOWARD... BUT NOT AS FAR AS... THE DYNAMICAL CONSENSUS. DUE TO THE LARGE SPREAD OF THE MODELS... ESPECIALLY AT DAYS 3-5... THE UNCERTAINTY IN THIS TRACK FORECAST IS FAIRLY SIGNIFICANT. THERE IS NO CHANGE TO THE INTENSITY FORECAST OR SUPPORTING REASONING. AN ENVIRONMENT OF WEAK VERTICAL WIND SHEAR PROVIDED BY A LARGE UPPER-LEVEL ANTICYCLONE OVER THE WESTERN CARIBBEAN... AND WATERS WITH LARGE UPPER OCEANIC HEAT CONTENT... SHOULD LEAD TO STEADY STRENGTHENING DURING THE NEXT FEW DAYS. THIS APPEARS EVEN MORE LIKELY NOW GIVEN THE MORE CONCENTRATED CONVECTION NEAR THE CIRCULATION CENTER THIS EVENING. THE LATEST GFDL FORECASTS MORE STRENGTHENING... AND MORE RAPIDLY... THAN IN THE PREVIOUS FEW RUNS... WITH AN INTENSITY NEAR 115 KT IN ABOUT 36 HOURS. MEANWHILE THE SHIPS GUIDANCE REMAINS MORE CONSERVATIVE IN FORECASTING A HURRICANE IN 48-72 HOURS. THE NEW OFFICIAL FORECAST REMAINS IN BETWEEN AND IS ESSENTIALLY AN UPDATE OF THE PREVIOUS ADVISORY. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 17/0300Z 17.6N 79.7W 30 KT 12HR VT 17/1200Z 17.7N 80.2W 40 KT 24HR VT 18/0000Z 17.8N 80.9W 50 KT 36HR VT 18/1200Z 18.0N 81.9W 60 KT 48HR VT 19/0000Z 18.3N 83.0W 70 KT 72HR VT 20/0000Z 19.0N 85.0W 80 KT 96HR VT 21/0000Z 20.5N 86.5W 90 KT 120HR VT 22/0000Z 22.5N 87.5W 90 KT |
