000 WTNT43 KNHC 221501 TCDAT3 TROPICAL DEPRESSION EIGHTEEN DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 1100 AM EDT MON OCT 22 2012 SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE THAT THE LOW PRESSURE SYSTEM OVER THE SOUTHWESTERN CARIBBEAN SEA HAS ACQUIRED SUFFICIENT ORGANIZATION TO BE CLASSIFIED AS A TROPICAL DEPRESSION. THE EXACT CENTER IS STILL A LITTLE DIFFICULT TO PINPOINT...BUT THE SYSTEM HAS CLOSED SURFACE CIRCULATION...AND CONVECTIVE BANDING HAS INCREASED MARKEDLY SINCE OVERNIGHT. REFINEMENTS TO THE POSITION COULD BE REQUIRED LATER TODAY ONCE THE AIR FORCE HURRICANE HUNTER PLANE INVESTIGATES THE SYSTEM. THE DEPRESSION HAS BEEN MOVING SLOWLY SOUTHWESTWARD...AND THE INITIAL MOTION IS ESTIMATED TO BE 230/4 KT. THE CYCLONE IS CURRENTLY LOCATED TO THE SOUTH OF A MID-LEVEL RIDGE THAT EXTENDS ACROSS THE GULF OF MEXICO AND FLORIDA...AND THIS FEATURE SHOULD CAUSE THE DEPRESSION TO MOVE LITTLE DURING THE NEXT DAY OR SO. AFTER 24 HOURS...A DEVELOPING MID- TO UPPER-LEVEL TROUGH OVER CUBA SHOULD PULL THE DEPRESSION NORTH-NORTHEASTWARD TOWARD JAMAICA AND EASTERN CUBA. WHILE THE GLOBAL MODELS SHOW VARYING SCENARIOS BY THE END OF THE WEEK...THEY ALL AGREE ON A PERSISTENT NORTH- NORTHEASTWARD MOTION THROUGH DAY 5. THE NHC TRACK FORECAST IS VERY NEAR THE CENTER OF THE TIGHTLY PACKED GUIDANCE ENVELOPE. THE DEPRESSION IS LOCATED IN AN ENVIRONMENT THAT IS HIGHLY CONDUCIVE FOR STRENGTHENING...AT LEAST DURING THE NEXT 36 TO 48 HOURS. IN FACT...THERE IS A 50/50 CHANCE THAT THE DEPRESSION WILL STRENGTHEN BY AT LEAST 25 KT DURING THE NEXT 24 HOURS BASED ON THE RAPID INTENSIFICATION INDEX. THEREFORE...THE OFFICIAL FORECAST SHOWS FAIRLY QUICK STRENGTHENING DURING THE NEXT 48 HOURS...AND THE DEPRESSION COULD BE ON THE CUSP OF BECOMING A HURRICANE AS IT IS APPROACHING JAMAICA. AFTER 48 HOURS...VERTICAL SHEAR IS EXPECTED TO INCREASE SUBSTANTIALLY...AND NEARLY ALL THE GLOBAL MODELS SUGGEST THAT THE CYCLONE WILL TAKE ON MORE HYBRID CHARACTERISTICS...SUCH AS AN EXPANDING WIND FIELD TO THE NORTH AND ITS INTERACTION WITH A MID- TO UPPER-LEVEL LOW. THE OFFICIAL FORECAST THEREFORE SHOWS THE CYCLONE BECOMING A SUBTROPICAL STORM BY DAY 5. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 13.5N 78.0W 25 KT 30 MPH 12H 23/0000Z 13.7N 78.3W 35 KT 40 MPH 24H 23/1200Z 14.3N 78.1W 45 KT 50 MPH 36H 24/0000Z 15.7N 77.6W 55 KT 65 MPH 48H 24/1200Z 17.4N 77.0W 60 KT 70 MPH 72H 25/1200Z 20.5N 76.0W 55 KT 65 MPH...INLAND OVER CUBA 96H 26/1200Z 24.5N 74.5W 55 KT 65 MPH...OVER WATER 120H 27/1200Z 27.0N 73.0W 50 KT 60 MPH...SUBTROPICAL $$ FORECASTER BERG/AVILA