000 WTNT43 KNHC 260856 TCDAT3 HURRICANE SANDY DISCUSSION NUMBER 16 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 500 AM EDT FRI OCT 26 2012 THE STRUCTURE OF SANDY CONTINUES TO EVOLVE...AS SHEAR AND DRY AIR ASSOCIATED WITH THE UPPER-LOW TO THE SOUTHWEST HAVE DISPLACED MOST OF THE CONVECTION NORTH OF THE CENTER. AIRCRAFT DATA SHOW THAT WHILE THE CENTRAL PRESSURE HAS NOT CHANGED MUCH...THE PRESSURE GRADIENT AND WIND FIELD HAVE BROADENED SUBSTANTIALLY. AS A RESULT...WINDS FROM FLIGHT LEVEL DO NOT APPEAR TO BE MIXING DOWN TO THE SURFACE VERY EFFICIENTLY...AND THE INITIAL INTENSITY HAS BEEN LOWERED TO 70 KT. SANDY IS EXPECTED TO REMAIN NEAR HURRICANE STRENGTH FOR THE NEXT COUPLE OF DAYS. AFTERWARD...SOME RE- INTENSIFICATION IS SHOWN AS SANDY INTERACTS WITH A SHORTWAVE TROUGH...GIVEN THAT THE GLOBAL MODELS SHOW THE LARGE CYCLONE DEEPENING OFFSHORE OF THE CAROLINAS AND THE MID-ATLANTIC STATES. IT APPEARS THAT SANDY WILL MAINTAIN SOME TYPE OF WARM SECLUSION STRUCTURE UNTIL NEAR THE END OF THE PERIOD...ALTHOUGH IT IS POSSIBLE THAT SANDY COULD BECOME POST-TROPICAL A LITTLE SOONER THAN INDICATED HERE. THE INITIAL MOTION ESTIMATE IS TOWARD THE NORTHWEST OR 325/11. AS SANDY CONTINUES TO INTERACT WITH THE UPPER-LOW IT WILL SLOW DOWN TODAY AND TONIGHT BEFORE ACCELERATING NORTHEASTWARD ON SATURDAY. THE NHC TRACK FORECAST IS A LITTLE TO THE LEFT OF THE PREVIOUS ONE THROUGH 36 HOURS AND LIES BETWEEN THE GFS AND ECMWF MODELS. LATE IN THE PERIOD...WHILE ALL OF THE GUIDANCE SHOWS SANDY TURNING NORTHWESTWARD...THERE CONTINUES TO BE LARGE SPREAD IN THE EXACT TRACK. THE ECMWF...GFDL...HWRF...AND SOME OF THE HFIP GUIDANCE SHOW A SHARPER TURN TOWARD THE DELMARVA PENINSULA...WHILE THE GFS AND UKMET SHOW A WIDER TURN WITH A TRACK FARTHER NORTH TOWARD LONG ISLAND. THE OFFICIAL FORECAST CONTINUES TO LIE BETWEEN THE ECMWF AND THE TVCA MULTI-MODEL CONSENSUS AT DAYS 4 AND 5...AND IS JUST A LITTLE TO THE LEFT OF THE PREVIOUS TRACK. USERS ARE REMINDED TO NOT FOCUS ON THE DETAILS OF THE TRACK FORECAST LATE IN THE PERIOD...AS SANDY IS EXPECTED TO BRING IMPACTS TO A LARGE PART OF THE U.S. EAST COAST INTO EARLY NEXT WEEK. GIVEN THE NEW NHC FORECAST AND THE EXPECTED GROWTH IN THE SIZE OF THE OUTER WIND FIELD...A TROPICAL STORM WATCH HAS BEEN ISSUED FOR PORTIONS OF THE COAST OF NORTH AND SOUTH CAROLINA ON THIS ADVISORY. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 26.3N 76.9W 70 KT 80 MPH 12H 26/1800Z 27.2N 77.5W 70 KT 80 MPH 24H 27/0600Z 28.3N 77.5W 65 KT 75 MPH 36H 27/1800Z 29.7N 76.4W 65 KT 75 MPH 48H 28/0600Z 31.4N 74.7W 65 KT 75 MPH 72H 29/0600Z 35.5N 72.5W 70 KT 80 MPH 96H 30/0600Z 38.5N 74.5W 70 KT 80 MPH 120H 31/0600Z 40.5N 77.5W 50 KT 60 MPH...POST-TROPICAL $$ FORECASTER BRENNAN