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| #56698 (Received by flhurricane at: 10:00 PM 13.Nov.2005) TCDAT2 TROPICAL DEPRESSION TWENTY-SEVEN DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 10 PM EST SUN NOV 13 2005 SATELLITE IMAGERY... SURFACE OBSERVATIONS... AND RADAR DATA FROM MARTINIQUE INDICATE THUNDERSTORM ACTIVITY HAS CONTINUED TO INCREASE AND BECOME MUCH BETTER ORGANIZED IN ASSOCIATION WITH THE LARGE LOW PRESSURE SYSTEM LOCATED OVER THE SOUTHEASTERN CARIBBEAN SEA. AT 14/0000Z... ST. LUCIA REPORTED SUSTAINED SOUTHEAST WINDS OF 29 KT ...AND SHIP ZCBU6 LOCATED JUST OFF THE SOUTHWEST COAST OF REPORTED SOUTHEAST WINDS OF 27 KT. SURFACE PRESSURE ANALYSES AT 00Z SUPPORT A MINIMUM CENTRAL PRESSURE OF AT LEAST 1007 MB... CORRESPONDING TO APPROXIMATELY 32 KT. RADAR DATA FROM MARTINIQUE SHOW CURVED CONVECTIVE BANDING HAS DEVELOPED NEAR AND EAST OF THE LOW-LEVEL CENTER... WHICH IS COINCIDENT WITH THE LARGE AREA OF -80C TO -82C CONVECTIVE TOPS THAT HAVE BEEN NOTED IN INFRARED SATELLITE IMAGERY SINCE 22Z. THEREFORE... THE LOW PRESSURE SYSTEM HAS BEEN UPGRADED TO TROPICAL DEPRESSION TWENTY-SEVEN. THE INITIAL MOTION ESTIMATE IS 300/09. THE DEPRESSION IS STILL IN THE FORMATIVE STAGES... SO THERE MAY SOME ERRATIC MOTION FOR THE NEXT 24 HOURS UNTIL THE CONVECTION BECOMES MORE CONSOLIDATED AROUND THE CENTER. HOWEVER... THE GENERAL TREND BY THE VARIOUS GLOBAL MODELS AND THE GFDL MODEL IS FOR THE CYCLONE TO PROPAGATE WEST-NORTH OR NORTHWESTWARD FOR THE NEXT 24-36 HOURS TOWARD A WEAKNESS IN THE SUBTROPICAL RIDGE LOCATED OVER THE NORTHEASTERN CARIBBEAN SEA AND NORTHERN LESSER ANTILLES. AFTER THAT... THE UPPER-LEVEL TROUGH THAT HAS CREATED THE WEAKNESS IS FORECAST TO SLOWLY WEAKEN AND LIFT OUT TO THE NORTHEAST... ALLOWING THE RIDGE TO BUILD EASTWARD TO THE NORTH AND NORTHEAST OF THE CYCLONE. THIS SHOULD ACT TO THE DRIVE THE STORM WESTWARD ACROSS THE CENTRAL CARIBBEAN SEA IN THE 48-120 HOUR FORECAST PERIODS. THE OFFICIAL FORECAST TRACK IS CLOSE TO A BLEND OF THE NOGAPS... UKMET... AND GFDL MODELS. UPPER-LEVEL WESTERLY SHEAR OF 20-25 KT IS EXPECTED TO CONTINUE ACROSS THE CYCLONE FOR THE NEXT 36-48 HOURS... WHICH SHOULD INHIBIT ANY RAPID DEVELOPMENT DURING THAT TIME. AFTERWARDS... THE SHEAR IS EXPECTED TO DECREASE TO LESS THAN 10 KT... AT WHICH TIME MORE SIGNIFICANT DEVELOPMENT COULD OCCUR. THE SHIPS MODEL BRINGS THE INTENSITY UP TO 66 KT IN 108 HOURS... WHEREAS THE GFDL MAKES THE CYCLONE A 112-KT MAJOR HURRICANE AT THE SAME TIME. IT SHOULD BE POINTED OUT THAT THE SHIPS INTENSITY MODEL FORECAST WAS BASED ON THE MEDIUM BAM MODEL FORECAST TRACK... WHICH TAKES THE STORM SOUTHWESTWARD ACROSS COLOMBIA WHERE UPPER-LEVEL WINDS ARE EXPECTED TO BE MUCH STRONGER THAN THEY ARE OVER THE CENTRAL CARIBBEAN SEA. IT IS QUITE POSSIBLE THAT THIS SYSTEM COULD END UP STRONGER THAN INDICATED AFTER 72 HOURS... GIVEN THE MUCH LOWER VERTICAL WIND SHEAR THAT THE GLOBAL MODELS ARE FORECASTING TO BE IN PLACE OVER THE 96- AND 120-HOUR OFFICIAL FORECAST POSITIONS. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 14/0300Z 13.5N 62.7W 30 KT 12HR VT 14/1200Z 14.3N 64.1W 30 KT 24HR VT 15/0000Z 15.3N 65.7W 35 KT 36HR VT 15/1200Z 15.9N 67.2W 35 KT 48HR VT 16/0000Z 16.1N 68.8W 40 KT 72HR VT 17/0000Z 16.0N 72.2W 45 KT 96HR VT 18/0000Z 16.0N 75.5W 50 KT 120HR VT 19/0000Z 16.0N 79.0W 60 KT |
