000 WTNT43 KNHC 240903 TCDAT3 TROPICAL STORM SANDY DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 500 AM EDT WED OCT 24 2012 REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT ABOUT 4 HOURS AGO INDICATED 850-MB FLIGHT-LEVEL WINDS OF 68 KT AND SFMR-ADJUSTED SURFACE WIND ESTIMATES OF 55 KT. THE MINIMUM CENTRAL PRESSURE WAS ESTIMATED TO BE 986 MB. SINCE THEN...DEEP CONVECTION WITH CLOUD TOPS AS COLD AS -90C HAVE ALMOST COMPLETELY ENCIRCLED THE CENTER OF SANDY AND NOAA BUOY 42058 RECENTLY REPORTED A SUSTAINED WIND OF 49 KT WITH A GUST TO 64 KT MORE THAN 160 N MI EAST OF THE CENTER. BASED ON THESE DATA...THE INITIAL INTENSITY IS RAISED TO 60 KT. SANDY IS MOVING FASTER TOWARD THE NORTH NOW...OR 010/12 KT. THE FORECAST SCENARIO AND THE FORECAST TRACK REMAIN UNCHANGED THROUGH 48-72 HOURS. SANDY SHOULD MOVE GENERALLY NORTHWARD FOR THE NEXT 48 HOURS AS THE CYCLONE INTERACTS OR MERGES WITH A POTENT MID- TO UPPER-LEVEL TROUGH SITUATED TO ITS NORTHWEST AND A MID-LEVEL RIDGE TO THE NORTH THAT IS SLIDING EASTWARD. AFTER 72 HR...SOUTHWESTERLY MID/UPPER-LEVEL FLOW ASSOCIATED WITH A SECOND DIGGING TROUGH OVER THE EASTERN UNITED STATES IS FORECAST TO TURN THE CYCLONE NORTHEASTWARD. THE NHC MODEL GUIDANCE HAS TRENDED A LITTLE MORE NORTH AND WEST AFTER 72 HOURS...AND THE OFFICIAL FORECAST TRACK HAS BEEN NUDGED IN THAT DIRECTION. THE NEW FORECAST TRACK LIES NEAR THE CENTER OF THE GUIDANCE ENVELOPE...AND IS BETWEEN THE PREVIOUS ADVISORY TRACK AND THE CONSENSUS MODELS TVCA AND TV15...AND THE FLORIDA STATE SUPERENSEMBLE MODEL. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE FOR ADDITIONAL STRENGTHENING TO OCCUR UP UNTIL SANDY MAKES LANDFALL ON JAMAICA IN ABOUT 12 HOURS OR SO. AFTER THAT...LAND INTERACTION WITH JAMAICA AND EASTERN CUBA...COMBINED WITH INCREASING SOUTHWESTERLY VERTICAL WIND SHEAR SHOULD INDUCE SOME GRADUAL WEAKENING. HOWEVER...THE AMOUNT OF WEAKENING THAT TYPICALLY OCCURS UNDER SUCH NEGATIVE CONDITIONS IS EXPECTED TO BE LIMITED DUE TO STRONG BAROCLINIC INTERACTION/FORCING ASSOCIATED WITH THE STRONG UPPER-LEVEL TROUGH. THE NHC INTENSITY FORECAST FOLLOWS THE TREND OF THE PREVIOUS ADVISORY IN SHOWING A 60-KT INTENSITY AFTER 36 HOURS AND THE CYCLONE BECOMING POST-TROPICAL BY 120 HOURS. HOWEVER... THIS REMAINS A LOW CONFIDENCE FORECAST FOR BOTH THE INTENSITY AND THE STRUCTURE OF THE CYCLONE AFTER 48-72 HOURS DUE TO UNCERTAINTY IN THE AMOUNT OF BAROCLINIC INTERACTION. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 16.3N 77.0W 60 KT 70 MPH 12H 24/1800Z 17.9N 76.8W 70 KT 80 MPH...NEAR JAMAICA 24H 25/0600Z 20.6N 76.5W 65 KT 75 MPH...INLAND EASTERN CUBA 36H 25/1800Z 23.3N 76.5W 60 KT 70 MPH...OVER WATER 48H 26/0600Z 25.7N 76.6W 60 KT 70 MPH 72H 27/0600Z 28.2N 76.3W 60 KT 70 MPH 96H 28/0600Z 31.0N 73.6W 60 KT 70 MPH 120H 29/0600Z 33.4N 70.3W 60 KT 70 MPH...POST-TROPICAL $$ FORECASTER STEWART