000 WTNT43 KNHC 241505 TCDAT3 HURRICANE SANDY DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 1100 AM EDT WED OCT 24 2012 DATA FROM THE HURRICANE HUNTER AIRCRAFT INDICATE THAT SANDY HAS REACHED HURRICANE STRENGTH. THE AIRCRAFT JUST MEASURED A PEAK 700-MB FLIGHT-LEVEL WIND OF 86 KT...AND BLENDING THAT WITH THE PEAK SFMR WINDS YIELDS AN INITIAL INTENSITY OF 70 KT. THE CENTRAL PRESSURE HAS ALSO FALLEN TO 973 MB BASED ON DATA FROM THE PLANE. CONDITIONS APPEAR FAVORABLE FOR ADDITIONAL INTENSIFICATION UNTIL THE CYCLONE MOVES NEAR OR OVER EASTERN JAMAICA...AND THE OFFICIAL FORECAST SHOWS SOME STRENGTHENING AT 12 HOURS. AFTER THAT TIME... ADDITIONAL LAND INTERACTION WITH EASTERN CUBA AND STRUCTURAL CHANGES DUE TO INTERACTION WITH AN UPPER-LEVEL TROUGH MAKE THE INTENSITY FORECAST HIGHLY UNCERTAIN. INCREASING SHEAR SHOULD RESULT IN LESS FAVORABLE CONDITIONS FOR INTENSIFICATION VIA LATENT HEAT RELEASE...BUT THIS COULD BE COMPENSATED FOR BY BAROCLINIC PROCESSES. GIVEN THE UNCERTAINTY...THE NHC INTENSITY FORECAST REMAINS UNCHANGED AT 36 HOURS AND BEYOND...SHOWING SANDY BECOMING A POWERFUL POST-TROPICAL CYCLONE BY THE END OF THE PERIOD. THE INITIAL MOTION IS 015/11. THE SHORT-TERM TRACK FORECAST REASONING REMAINS UNCHANGED FOR THE FIRST COUPLE OF DAYS...AS SANDY SHOULD MOVE GENERALLY NORTHWARD INTO A BREAK IN THE SUBTROPICAL RIDGE OVER THE BAHAMAS AS IT INTERACTS WITH AN UPPER-LEVEL LOW TO ITS WEST. LATE IN THE PERIOD...THERE REMAINS CONSIDERABLE SPREAD IN THE GUIDANCE DUE TO DIFFERENCES IN HOW MUCH SANDY INTERACTS WITH ANOTHER TROUGH MOVING INTO THE NORTHEASTERN UNITED STATES. THE ECMWF HAS BEEN CONSISTENT IN SHOWING MORE INTERACTION AND A TRACK FARTHER WEST...WHILE THE GFS SHOWS SANDY TURNING EAST AND MISSING THE TROUGH. OVERALL MORE OF THE GUIDANCE HAS BEEN TRENDING TOWARD SHOWING MORE INTERACTION WITH THE EASTERN U.S. TROUGH LATE IN THE PERIOD. GIVEN THIS TREND...THE NHC FORECAST HAS BEEN ADJUSTED TO THE LEFT AT DAYS 4 AND 5...AND LIES ROUGHLY BETWEEN THE ECMWF AND THE TVCA MULTI-MODEL CONSENSUS. NEEDLESS TO SAY...THE TRACK FORECAST UNCERTAINTY REMAINS HIGH AT THE END OF THE PERIOD. GIVEN THE LATEST NHC FORECAST...A HURRICANE WATCH HAS BEEN ISSUED FOR THE CENTRAL AND NORTHWEST BAHAMAS...AND THE TROPICAL STORM WATCH HAS BEEN EXTENDED NORTHWARD ALONG THE EAST-CENTRAL FLORIDA COAST. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 17.1N 76.7W 70 KT 80 MPH 12H 25/0000Z 19.1N 76.5W 75 KT 85 MPH 24H 25/1200Z 21.9N 76.4W 65 KT 75 MPH 36H 26/0000Z 24.4N 76.4W 60 KT 70 MPH 48H 26/1200Z 26.3N 76.7W 60 KT 70 MPH 72H 27/1200Z 28.7N 76.0W 60 KT 70 MPH 96H 28/1200Z 32.0N 73.0W 60 KT 70 MPH 120H 29/1200Z 35.5N 70.0W 60 KT 70 MPH...POST-TROPICAL $$ FORECASTER BRENNAN