000 WTNT43 KNHC 251446 TCDAT3 HURRICANE SANDY DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 1100 AM EDT THU OCT 25 2012 THE SATELLITE PRESENTATION OF SANDY HAS BECOME A LITTLE LESS IMPRESSIVE AFTER MOVING OVER EASTERN CUBA. THE EYE IS NO LONGER APPARENT IN IMAGERY OR IN OBSERVATIONS FROM THE AIRCRAFT...AND THE CDO HAS BECOME SOMEWHAT DISRUPTED ON THE WESTERN SIDE BY SOUTHWESTERLY FLOW FROM AN UPPER-LEVEL LOW TO THE WEST. HOWEVER... AIRCRAFT DATA INDICATE THAT THE CIRCULATION ASSOCIATED WITH SANDY REMAINS QUITE STRONG...WITH A PEAK FLIGHT-LEVEL WIND AT 700 MB OF 126 KT AND A CENTRAL PRESSURE OF 964 MB. DATA FROM THE SFMR AND DROPSONDES SUGGEST THAT THE WINDS FROM FLIGHT LEVEL ARE NOT CURRENTLY MIXING DOWN TO THE SURFACE AT THE TYPICAL RATIO...SO A BLEND OF THE DATA SUPPORT MAINTAINING AN INTENSITY OF 90 KT FOR THIS ADVISORY. A CONTINUED INCREASE IN SHEAR AND INTERACTION WITH THE UPPER-LEVEL LOW SHOULD RESULT IN GRADUAL WEAKENING DURING THE NEXT COUPLE OF DAYS. HOWEVER...DURING THIS TIME THE OUTER WIND FIELD OF SANDY IS EXPECTED TO EXPAND...AND SANDY IS FORECAST TO BE A LARGE CYCLONE AT OR NEAR HURRICANE INTENSITY THROUGH THE END OF THE FORECAST PERIOD. THE INITIAL MOTION ESTIMATE IS 360/14...AFTER A BIT OF A JOG TO THE RIGHT EARLIER THIS MORNING. THE REASONING FOR THE SHORT-TERM PORTION OF THE TRACK FORECAST REMAINS UNCHANGED. SANDY SHOULD MOVE NORTHWARD TODAY AND SLOW DOWN AS IT TURNS NORTH-NORTHWESTWARD ON FRIDAY WHEN IT INTERACTS WITH THE AFOREMENTIONED UPPER-LEVEL LOW. SANDY SHOULD THEN TURN NORTH-NORTHEASTWARD BY 72 HOURS AHEAD OF A LONGWAVE TROUGH MOVING THROUGH THE EASTERN UNITED STATES. AFTER THAT TIME...THE TRACK MODEL GUIDANCE CONTINUES TO TREND TOWARD A NORTHWESTWARD TURN AS SANDY INTERACTS WITH AN AMPLIFYING SHORTWAVE TROUGH OVER THE MID-ATLANTIC STATES. HOWEVER...THERE REMAIN SIGNIFICANT DETAIL DIFFERENCES IN REGARD TO THE TIMING OF THIS INTERACTION AND WHERE THE NORTHWEST TURN WILL OCCUR. THE ECMWF AND GFDL MODELS SHOW A QUICKER TURN...BRINGING THE CENTER INLAND BY DAY 5. MUCH OF THE REST OF THE GUIDANCE SUGGESTS A MORE GRADUAL TURN WITH THE CENTER STILL OFFSHORE AT 120 HOURS. THE NHC FORECAST HAS BEEN SHIFTED WESTWARD AT DAYS 4 AND 5 AND LIES ABOUT HALFWAY BETWEEN THE ECMWF AND THE GFS ENSEMBLE MEAN AND CLOSE TO THE ECMWF ENSEMBLE MEAN. REGARDLESS OF THE EXACT TRACK OF SANDY...IT IS LIKELY THAT SIGNIFICANT IMPACTS WILL BE FELT OVER PORTIONS OF THE U.S. EAST COAST THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. NOTE THAT THE TROPICAL CYCLONE WIND SPEED PROBABILITIES ARE NOT DESIGNED TO HANDLE THE TYPE OF STRUCTURAL CHANGES ANTICIPATED WITH SANDY DURING THE FORECAST PERIOD. AS A RESULT...THESE PROBABILITIES WILL UNDERESTIMATE THE ACTUAL RISK OF STRONG WINDS AWAY FROM THE CENTER OF SANDY. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 22.4N 75.5W 90 KT 105 MPH 12H 26/0000Z 24.4N 75.6W 90 KT 105 MPH 24H 26/1200Z 26.2N 76.4W 80 KT 90 MPH 36H 27/0000Z 27.4N 76.9W 75 KT 85 MPH 48H 27/1200Z 28.9N 76.3W 70 KT 80 MPH 72H 28/1200Z 32.0N 73.5W 65 KT 75 MPH 96H 29/1200Z 36.0N 72.0W 65 KT 75 MPH 120H 30/1200Z 39.5N 73.5W 60 KT 70 MPH...POST-TROPICAL $$ FORECASTER BRENNAN