ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM HURRICANE SANDY DISCUSSION NUMBER 28 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012 500 AM EDT MON OCT 29 2012 SANDY CONTINUES TO MAINTAIN AN AREA OF DEEP CONVECTION NEAR THE CENTER...WITH AN EYE OCCASIONALLY VISIBLE ON SATELLITE IMAGERY. ALTHOUGH THE SATELLITE PRESENTATION OF THE SYSTEM IS NOT VERY IMPRESSIVE...SFMR MEASUREMENTS...FLIGHT-LEVEL WINDS...AND DROPSONDE DATA FROM THE AIR FORCE HURRICANE HUNTERS INDICATE THAT THE WINDS HAVE INCREASED TO NEAR 75 KT. SINCE THE HURRICANE WILL TRAVERSE THE GULF STREAM THIS MORNING...AND THE SHEAR IS NOT TOO STRONG AT THIS TIME...SOME MORE STRENGTHENING AS A TROPICAL CYCLONE IS POSSIBLE IN THE NEXT FEW HOURS. HOWEVER...THE MAIN MECHANISM FOR INTENSIFICATION LATER TODAY SHOULD BE BAROCLINIC FORCING. THE OFFICIAL WIND SPEED FORECAST IS CLOSE TO THE LATEST GFS PREDICTION AS THAT MODEL SHOULD BE ABLE TO HANDLE THE EVOLUTION OF THIS TYPE OF SYSTEM FAIRLY WELL. SURFACE DATA INDICATE THAT A WELL-MARKED WARM AND COLD FRONT LIE NOT FAR TO THE NORTH AND WEST OF THE CENTER OF SANDY. AS THE CIRCULATION INTERACTS WITH THESE FRONTS...THE CYCLONE SHOULD BECOME EXTRATROPICAL LATER TODAY. EXTRATROPICAL TRANSITION IS EXPECTED TO BE COMPLETE BEFORE THE CENTER CROSSES 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. CENTER FIXES INDICATE THAT SANDY IS NOW MOVING NORTHWARD OR ABOUT 360/13...AS IT BEGINS TO ROTATE AROUND A MID- TO UPPER-LEVEL CYCLONE OVER THE SOUTHEASTERN UNITED STATES. AS IT MOVES BETWEEN THE CYCLONE AND A HIGHLY ANOMALOUS MID-TROPOSPHERIC RIDGE NEAR ATLANTIC CANADA...SANDY SHOULD TURN NORTHWESTWARD AND WEST-NORTHWESTWARD WITH SOME FURTHER INCREASE IN FORWARD SPEED. THIS TRACK SHOULD RESULT IN THE CENTER MAKING LANDFALL IN THE MID-ATLANTIC STATES THIS EVENING OR TONIGHT. AFTER LANDFALL...THE DYNAMICAL GUIDANCE SHOWS A SIGNIFICANT SLOWING OF FORWARD SPEED AS THE SYSTEM MERGES WITH THE MID- TO UPPER-LEVEL CYCLONE. THE OFFICIAL TRACK FORECAST FOR THIS PACKAGE IS A BIT FASTER THAN THE PREVIOUS ONE...AND CLOSE TO THE GFS AND ECMWF SOLUTIONS. 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. 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 29/0900Z 35.9N 70.5W 75 KT 85 MPH 12H 29/1800Z 37.8N 72.0W 80 KT 90 MPH 24H 30/0600Z 39.5N 75.5W 65 KT 75 MPH...POST-TROP/EXTRATROP 36H 30/1800Z 40.0N 77.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 31/0600Z 40.5N 77.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 01/0600Z 44.0N 76.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 96H 02/0600Z 45.5N 74.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 120H 03/0600Z 46.5N 70.0W 20 KT 25 MPH...POST-TROP/EXTRATROP $$ FORECASTER PASCH/CANGIALOSI NNNN
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Page last modified: Monday, 31-Dec-2012 12:09:56 UTC