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| #156818 (Received by flhurricane at: 11:08 PM 27.Oct.2007) TCDAT1 TROPICAL DEPRESSION SIXTEEN DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL162007 1100 PM EDT SAT OCT 27 2007 THE AREA OF LOW PRESSURE IN THE CARIBBEAN SEA HAS DEVELOPED ENOUGH ORGANIZED CONVECTION TO BE CLASSIFIED AS A TROPICAL DEPRESSION...WITH A LARGE CONVECTIVE MASS TO THE EAST AND NORTHEAST OF THE PARTLY EXPOSED LOW-LEVEL CENTER. SATELLITE INTENSITY ESTIMATES ARE 30 KT FROM TAFB AND 25 KT FROM SAB...WHILE QUIKSCAT DATA SHOWED NO RELIABLE WINDS HIGHER THAN 30 KT. BASED ON THIS...THE INITIAL INTENSITY IS SET AT 30 KT. THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 290/6. THE LARGE CYCLONIC ENVELOPE OF THE DEPRESSION IS LOCATED SOUTH OF A LOW/MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC...WITH AN UPPER-LEVEL LOW OVER HAITI AND SURFACE TROUGHS OVER THE NORTHWESTERN CARIBBEAN AND GULF OF MEXICO. THE LARGE-SCALE MODELS GENERALLY FORECAST THE ATLANTIC RIDGE TO GRADUALLY WEAKEN...WITH A MID/UPPER-LEVEL SHORTWAVE TROUGH MOVING INTO THE SOUTHEASTERN UNITED STATES BY 96-120 HR. THE TRACK GUIDANCE RESPONDS TO THIS EVOLUTION WITH A RANGE OF POSSIBILITIES. THE UKMET KEEPS THE SYSTEM SOUTH OF CUBA BY 120 HR...WHILE THE NOGAPS FORECASTS IT TO REACH THE SOUTHEASTERN GULF OF MEXICO BY THAT TIME. THE GFS AND ECMWF FORECAST THE CYCLONE TO TURN NORTHWARD BY 72-96 HR...THEN EITHER RECURVE OR RE-FORM NORTHEASTWARD INTO THE NORTHERN BAHAMAS. THE GFDL AND THE HWRF CALL FOR A TRACK ACROSS HAITI AND THE CENTRAL BAHAMAS INTO THE ATLANTIC. THE TRACK FORECAST IS FURTHER COMPLICATED BY THE GFS...ECMWF...AND NOGAPS SHOWING THE SEPARATION OF THE LOW-LEVEL AND MID-LEVEL CENTERS BY 96-120 HR DUE TO SHEAR. THE TRACK FORECAST IS DOWN THE MIDDLE OF THIS SPREAD...WITH A NORTHWESTWARD MOTION THROUGH 72 HR FOLLOWED BY A SLOW RECURVATURE INTO THE WESTERLIES. IT IS IN BEST AGREEMENT WITH THE GFS AND ECMWF. THE COMBINATION OF THE LARGE SIZE OF THE DEPRESSION AND VERTICAL WIND SHEAR FROM THE UPPER-LEVEL LOW SHOULD SLOW DEVELOPMENT DURING THE FIRST 36 HR OR SO. AFTER THAT...THE LARGE-SCALE MODELS BUILD A LARGE UPPER-LEVEL ANTICYCLONE OVER THE WESTERN CARIBBEAN THAT COULD PRODUCE A MORE FAVORABLE ENVIRONMENT FOR STRENGTHENING...IF THE CYCLONE IS UNDER IT RATHER THAN NORTH OF IT AS CURRENTLY FORECAST. THE GFDL AND HWRF MAKE THE SYSTEM A HURRICANE OVER THE ATLANTIC DESPITE STRONG SHEAR. DUE TO THE UNCERTAINTY...THE INTENSITY FORECAST CALLS FOR GRADUALLY STRENGTHENING THROUGH 72 HR...BELOW THAT OF THE SHIPS...GFDL..AND HWRF. AFTER 72 HR...LITTLE CHANGE IN STRENGTH IS FORECAST DUE TO A COMBINATION OF LAND INTERACTION AND INCREASING SHEAR ALONG THE FORECAST TRACK. BOTH THE TRACK AND INTENSITY FORECASTS HAVE GREATER THAN NORMAL UNCERTAINTY AT THIS TIME. FORECAST POSITIONS AND MAX WINDS INITIAL 28/0300Z 15.9N 71.5W 30 KT 12HR VT 28/1200Z 16.6N 72.6W 35 KT 24HR VT 29/0000Z 17.7N 74.2W 40 KT 36HR VT 29/1200Z 18.8N 76.0W 45 KT 48HR VT 30/0000Z 19.6N 77.6W 50 KT 72HR VT 31/0000Z 21.0N 80.0W 60 KT 96HR VT 01/0000Z 22.5N 80.0W 60 KT...INLAND 120HR VT 02/0000Z 25.0N 78.5W 60 KT $$ FORECASTER BEVEN |
