000 WTNT43 KNHC 291443 TCDAT3 HURRICANE SANDY DISCUSSION NUMBER 29 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 1100 AM EDT MON OCT 29 2012 SANDY IS MAINTAINING A SMALL AREA OF DEEP CONVECTION NEAR THE CENTER...WITH BOTH AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT DATA AND VARIOUS MICROWAVE SATELLITE DATA INDICATING A 20 N MI DIAMETER EYE HAS DEVELOPED SINCE THE PREVIOUS ADVISORY. MAXIMUM 700 MB FLIGHT-LEVEL WINDS HAVE BEEN 94 KT IN THE SOUTHERN QUADRANT...AND SFMR-ADJUSTED SURFACE WINDS OF 80-83 KT HAVE BEEN OBSERVED IN THE SOUTHWESTERN QUADRANT MORE THAN 90 N MI FROM THE CENTER. THE AIRCRAFT DATA ALSO INDICATE THAT THE CENTRAL PRESSURE HAS FALLEN A LITTLE...TO ABOUT 943 MB. BASED ON THE LATEST RECONNAISSANCE DATA...THE INITIAL INTENSITY HAS BEEN INCREASED TO 80 KT. RECONNAISSANCE CENTER FIXES INDICATE THAT SANDY HAS BEEN GRADUALLY TURNING TO THE LEFT AND IS NOW MOVING NORTH-NORTHWESTWARD OR ABOUT 330/16 KT. THE LATEST RECON FIXES HAVE BEEN FALLING ON THE PREVIOUS FORECAST TRACK...AND SO HAVE THE LATEST 12Z NHC FORECAST MODELS. THEREFORE...NO SIGNIFICANT CHANGES TO THE ADVISORY PREVIOUS TRACK OR REASONING ARE REQUIRED. SANDY IS NOW LOCATED NORTH OF THE AXIS OF A STRONG NEGATIVELY TILTED MID-/UPPER-LEVEL TROUGH...AND THE HURRICANE SHOULD TURN NORTHWESTWARD VERY SOON. LANDFALL ALONG OR JUST SOUTH OF THE SOUTHERN NEW JERSEY COAST IS EXPECTED LATE THIS EVENING...AT WHICH TIME A TURN TO THE WEST-NORTHWEST IS EXPECTED. AFTER MOVING INLAND OVER THE MID-ATLANTIC STATES A DECREASE IN FORWARD SPEED IS EXPECTED. BY 48 HOURS...THE POST-TROPICAL CYCLONE IS FORECAST TO MOVE NORTHWARD AND THEN NORTHEASTWARD. THE OFFICIAL NHC FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY TRACK...AND LIES CLOSE TO A BLEND OF THE CONSENSUS MODELS TV15 AND TVCN. SANDY IS CURRENTLY TRAVERSING A NARROW RIDGE OF WARM SSTS AROUND 27C...WHICH ARE ASSOCIATED WITH THE GULF STREAM. THIS EXTRA LOW-LEVEL HEAT INPUT HAS LIKELY CONTRIBUTED TO THE RECENT INCREASE IN CONVECTION AROUND THE EYE. HOWEVER...SANDY WILL BE MOVING OVER THE NORTH WALL OF THE GULFSTREAM WITHIN THE NEXT 3 HOURS...WHICH WILL BRING A HALT TO ANY SIGNIFICANT INNER-CORE CONVECTIVE DEVELOPMENT. HOWEVER...THIS SHOULD HAVE LITTLE IMPACT ON THE OVERALL INTENSITY OR THE SIZE OF THE EXTREMELY LARGE WIND FIELD THAT IS NOW MORE THAN 1000 N MI IN DIAMETER. AT THE MOMENT... HURRICANE FORCE WINDS ARE ONLY OCCURRING IN THE SOUTHWEST QUADRANT...BUT MODEL GUIDANCE SUGGESTS THAT THESE COULD SPREAD INTO THE NORTHERN SEMICIRCLE BEFORE LANDFALL. SURFACE DATA INDICATE THAT WELL-DEFINED WARM AND COLD FRONTS LIE VERY NEAR THE CENTER OF SANDY...AND THE COMBINATION OF COLDER OCEAN WATER AND NEARBY FRONTAL SYSTEMS ARE EXPECTED TO RESULT IN EXTRATROPICAL TRANSITION BEFORE THE CENTER OF THE CYCLONE REACHES THE COAST. HOWEVER...THIS TRANSFORMATION WILL NOT DIMINISH THE OVERALL IMPACTS FROM WINDS TO HURRICANE STRENGTH...LIFE-THREATENING STORM SURGE... AND FLOODING RAINS ASSOCIATED WITH THIS DANGEROUS WEATHER SYSTEM. BASED ON THE GLOBAL MODELS...THE CYCLONE SHOULD WEAKEN FAIRLY RAPIDLY AFTER LANDFALL. INTERESTS ARE REMINDED NOT TO FOCUS ON THE CENTER OR THE EXACT FORECAST TRACK OF THIS SYSTEM...SINCE STRONG WINDS COVER AN AREA SEVERAL HUNDRED MILES ACROSS...AND THE HIGHEST WINDS WILL NOT NECESSARILY BE NEAR THE CENTER...ESPECIALLY JUST A FEW HUNDRED FEET ABOVE THE GROUND. AS NOTED IN PREVIOUS ADVISORIES...TO AVOID A HIGHLY DISRUPTIVE CHANGE FROM TROPICAL TO NON-TROPICAL WARNINGS WHEN SANDY BECOMES POST-TROPICAL...THE WIND HAZARD NORTH OF THE TROPICAL STORM WARNING AREA WILL CONTINUE TO BE CONVEYED THROUGH HIGH WIND WATCHES AND WARNINGS ISSUED BY LOCAL NATIONAL WEATHER SERVICE OFFICES. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 37.5N 71.5W 80 KT 90 MPH 12H 30/0000Z 39.0N 74.0W 80 KT 90 MPH...POST-TROP/EXTRATROP 24H 30/1200Z 39.9N 76.7W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 31/0000Z 40.4N 77.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 31/1200Z 41.5N 77.2W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 01/1200Z 44.5N 75.6W 30 KT 35 MPH...POST-TROP/EXTRATROP 96H 02/1200Z 45.9N 72.7W 25 KT 30 MPH...POST-TROP/EXTRATROP 120H 03/1200Z 47.5N 68.5W 20 KT 25 MPH...POST-TROP/EXTRATROP $$ FORECASTER STEWART
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