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Hurricane SANDY


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HURRICANE SANDY DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL182012
500 PM EDT THU OCT 25 2012
 
SATELLITE IMAGERY SHOWS THAT STRUCTURAL CHANGES ARE ALREADY
OCCURRING WITH SANDY. DRY AIR ALOFT AND SOUTHWESTERLY FLOW
ASSOCIATED WITH AN UPPER-LEVEL LOW CENTERED NEAR WESTERN CUBA ARE
IMPINGING ON THE WEST SIDE OF THE CIRCULATION. AS A RESULT...THE
OUTFLOW IS RESTRICTED IN THE SOUTHWEST QUADRANT AND THE CLOUD
PATTERN IS BECOMING MORE ASYMMETRIC. HOWEVER...THE HIGHEST FLIGHT-
LEVEL WINDS FROM THE AIRCRAFT WERE STILL 109 KT AT THE END OF THE
LAST MISSION AND THE CENTRAL PRESSURE REMAINS AT 963 MB. THE
INITIAL INTENSITY REMAINS 90 KT FOR THIS ADVISORY. SOME DECREASE IN
THE MAXIMUM WINDS IS EXPECTED DURING THE NEXT COUPLE OF DAYS AS
SANDY BECOMES MORE ENTANGLED WITH THE UPPER-LEVEL LOW...HOWEVER THE
GLOBAL MODELS SHOW SANDY REMAINING A VERY DEEP CYCLONE AND THE WIND
FIELD EXPANDING DURING THIS TIME. LATER IN THE PERIOD...SOME
RE-INTENSIFICATION IS SHOWN AS SANDY DEEPENS AGAIN OFF THE U.S.
EAST COAST WHILE IT INTERACTS WITH ANOTHER SHORTWAVE TROUGH.
REGARDLESS...SANDY IS EXPECTED TO BE A LARGE CYCLONE AT OR NEAR
HURRICANE INTENSITY THROUGH MOST OF THE FORECAST PERIOD.
 
THE INITIAL MOTION ESTIMATE IS 360/17...AS SANDY HAS BEGUN TO
ACCELERATE NORTHWARD DUE TO THE UPPER LOW. THE REASONING FOR THE
TRACK FORECAST REMAINS LARGELY UNCHANGED. SANDY WILL BE PULLED
NORTHWESTWARD AND SLOW DOWN ON FRIDAY WHILE IT INTERACTS WITH THE
UPPER-LEVEL LOW. THEN A NORTH-NORTHEASTWARD ACCELERATION IS
EXPECTED BY SATURDAY AS A LONGWAVE TROUGH MOVES INTO THE EASTERN
UNITED STATES. MOST OF THE TRACK MODELS NOW SHOW A TURN BACK TOWARD
THE NORTHWEST BY THE END OF THE PERIOD DUE TO SANDY INTERACTING
WITH AN AMPLIFYING SHORTWAVE TROUGH OVER THE CAROLINAS AND
MID-ATLANTIC STATES. HOWEVER...THERE REMAIN SOME SIGNIFICANT
DIFFERENCES IN THE TIMING OF THIS INTERACTION...AS THE ECMWF HAS
SANDY FARTHER WEST AND INTERACTING WITH THE SHORTWAVE SOONER
RELATIVE TO MOST OF THE REST OF THE GUIDANCE...WHICH SHOWS A WIDER
TURN AND A TRACK FARTHER NORTH. THE NEW NHC FORECAST IS CLOSE TO
THE PREVIOUS ONE...AND LIES ROUGHLY BETWEEN THE ECMWF AND THE GFS
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  25/2100Z 24.5N  75.6W   90 KT 105 MPH
 12H  26/0600Z 26.0N  76.0W   85 KT 100 MPH
 24H  26/1800Z 27.4N  77.0W   80 KT  90 MPH
 36H  27/0600Z 28.3N  77.0W   75 KT  85 MPH
 48H  27/1800Z 29.8N  76.0W   65 KT  75 MPH
 72H  28/1800Z 33.0N  73.0W   70 KT  80 MPH
 96H  29/1800Z 37.5N  72.5W   70 KT  80 MPH
120H  30/1800Z 40.5N  75.0W   55 KT  65 MPH...POST-TROPICAL
 
$$
FORECASTER BRENNAN
 
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