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Hurricane SANDY


ZCZC MIATCDAT3 ALL
TTAA00 KNHC DDHHMM
 
HURRICANE SANDY DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL182012
1100 PM EDT FRI OCT 26 2012

SANDY IS SHOWING CHARACTERISTICS OF A HYBRID CYCLONE THIS EVENING. 
OVERALL...THE SYSTEM LOOKS LIKE A LARGE OCCLUDED FRONTAL LOW. 
HOWEVER...SURFACE OBSERVATIONS DO NOT SHOW STRONG TEMPERATURE
GRADIENTS...AND CENTRAL CONVECTION IS OCCURRING IN BANDS TO THE
NORTHWEST OF THE CENTER.  IN ADDITION...AMSU DATA FROM NEAR 2000
UTC INDICATED THAT THE SYSTEM STILL HAD A DEEP WARM CORE. 
DROPSONDES AND SFMR DATA FROM A NOAA HURRICANE HUNTER AIRCRAFT
SHOWED A LARGE AREA OF 60 KT WINDS TO THE WEST AND NORTHWEST OF THE
CENTER...AND BASED ON THIS AND THE POSSIBILITY THAT STRONGER WINDS
WERE NOT SAMPLED...THE INITIAL INTENSITY REMAINS 65 KT.  AN
INTERESTING NOTE IS THAT THE DROPSONDE DATA INDICATES THAT THE
STRONGEST WINDS IN THE CONVECTION AT FLIGHT-LEVEL ARE SIGNIFICANTLY
LESS THAN THOSE NEAR THE SURFACE.

THE CENTER HAS BEEN WOBBLING DURING THE EVENING...WITH THE INITIAL
MOTION A SOMEWHAT UNCERTAIN 010/6.  THERE IS NO CHANGE TO THE TRACK
FORECAST REASONING FROM THE PREVIOUS ADVISORY.  A DEEP-LAYER TROUGH
MOVING INTO THE EASTERN UNITED STATES SHOULD CAUSE SANDY TO TURN
NORTHEASTWARD WITH AN INCREASE IN FORWARD SPEED...AND THIS MOTION
SHOULD PERSIST FOR 48 HR OR SO.  AFTER THAT...A NEGATIVELY-TILTED
SHORTWAVE TROUGH NEAR THE U.S. EAST COAST AND A RIDGE OVER EXTREME
EASTERN CANADA SHOULD CAUSE SANDY TO TURN TOWARD THE NORTHWEST AND
WEST-NORTHWEST...TOWARD AND OVER THE U.S. COAST.  THE TRACK
GUIDANCE ENVELOPE SHIFTED A LITTLE TO THE EAST DURING THE FIRST 48
HR...AND THE FORECAST IS NUDGED IN THAT DIRECTION.  HOWEVER...THERE
WAS LITTLE CHANGE AFTER THAT TIME...AND THE LANDFALL AREA AND TIME
IS CHANGED LITTLE FROM THAT OF THE PREVIOUS FORECAST.

SANDY IS CURRENTLY EXPERIENCING ABOUT 50 KT OF VERTICAL WIND SHEAR
WHICH IS DISRUPTING THE CONVECTIVE STRUCTURE.  HOWEVER...VERY
STRONG UPPER-LEVEL DIVERGENCE ASSOCIATED WITH A TROUGH SOUTHWEST OF
THE HURRICANE IS LIKELY SUSTAINING THE CYCLONE.  WHILE THESE
CONDITIONS ARE FORECAST TO CONTINUE...IT IS LIKELY THAT SANDY WILL
CONTINUE TO SLOWLY WEAKEN THROUGH 36 HR.  SUBSEQUENTLY...THE
DYNAMICAL MODELS FORECAST THAT INTERACTION WITH THE U. S. SHORTWAVE
TROUGH WILL CAUSE SANDY TO RE-INTENSIFY PRIMARILY DUE TO
BAROCLININC ENERGY PROCESSES.  THE INTENSITY FORECAST SHOWS SANDY
REGAINING HURRICANE STRENGTH IN 48-72 HR.  HOWEVER...THE CYCLONE
WILL BE UNDERGOING EXTRATROPICAL TRANSITION AS THIS HAPPENS...AND
WHEN THIS PROCESS WILL BE COMPLETE IS UNCERTAIN.  REGARDLESS OF THE
EXACT STRUCTURE AT LANDFALL...SANDY IS EXPECTED TO BE A LARGE AND
POWERFUL CYCLONE WITH SIGNIFICANT IMPACTS EXTENDING WELL AWAY FROM
THE LOCATION OF THE CENTER.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/0300Z 27.7N  77.1W   65 KT  75 MPH
 12H  27/1200Z 28.8N  76.7W   60 KT  70 MPH
 24H  28/0000Z 30.4N  75.2W   55 KT  65 MPH
 36H  28/1200Z 32.0N  73.3W   55 KT  65 MPH
 48H  29/0000Z 33.8N  71.9W   65 KT  75 MPH
 72H  30/0000Z 37.5N  72.0W   70 KT  80 MPH
 96H  31/0000Z 40.0N  77.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  01/0000Z 42.0N  76.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 
NNNN


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Page last modified: Monday, 31-Dec-2012 12:09:55 UTC