Hurricane GORDON

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HURRICANE GORDON DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012
1100 PM AST SUN AUG 19 2012
 
THE EYE DISAPPEARED ON SATELLITE IMAGERY SEVERAL HOURS AGO AND THE
CLOUD PATTERN IS BECOMING INCREASINGLY RAGGED.  A RECENT ASCAT PASS
OVER THE HURRICANE SHOWED THAT THE CENTER IS LOCATED IN THE
SOUTHWEST PART OF THE CLOUD MASS...BUT THAT THE CIRCULATION IS
STILL QUITE STRONG.  THE CURRENT INTENSITY ESTIMATE OF 70 KT IS
BASED ON AN ASSUMED SLOW WEAKENING RATE AND IS CONSISTENT WITH A
BLEND OF T- AND CI-NUMBERS FROM TAFB AND SAB.   THE COMBINATION OF
INCREASED SOUTHWESTERLY SHEAR AND COOLER WATERS SHOULD LEAD TO
STEADY WEAKENING.  GORDON IS LIKELY TO BECOME A POST-TROPICAL
CYCLONE IN 24-36 HOURS AND THE CYCLONE SHOULD DISSIPATE IN 72
HOURS OR LESS.   THE OFFICIAL INTENSITY FORECAST IS CLOSE TO THE
LATEST SHIPS OUTPUT...BUT IS IS WORTH NOTING THAT THE DIAGNOSTICS
FROM THAT MODEL SHOW GORDON LOSING TROPICAL CHARACTERISTICS ON
MONDAY.

NOW THAT THE CENTER HAS MORE BECOME DIFFICULT TO FIND...THE INITIAL
MOTION IS A RATHER UNCERTAIN 070/17...OR PERHAPS A LITTLE SLOWER.
THE HURRICANE CONTINUES TO BE EMBEDDED IN A WESTERLY CURRENT TO
THE SOUTH OF A LARGE LOW OVER THE NORTHEASTERN ATLANTIC.  AS THE
UPPER-LEVEL CIRCULATION OF GORDON IS LIKELY TO BE SHEARED AWAY BY
STRONG UPPER-LEVEL WINDS IN ABOUT 36 HOURS...GORDON OR ITS
POST-TROPICAL COUNTERPART SHOULD BECOME A SHALLOW CYCLONE STEERED
MAINLY BY THE WEAKER LOW-LEVEL FLOW.  THEREFORE A CONSIDERABLE
SLOWING OF THE FORWARD SPEED IS ANTICIPATED.  THE OFFICIAL TRACK
FORECAST IS CLOSE TO THE DYNAMICAL MODEL CONSENSUS BUT A BIT FASTER
THAN THE LATEST GFS TRACK.
 
THE INITIAL AND FORECAST WIND RADII HAVE BEEN ADJUSTED BASED ON THE
TIMELY ASCAT PASS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/0300Z 36.7N  25.8W   70 KT  80 MPH
 12H  20/1200Z 37.8N  23.3W   55 KT  65 MPH
 24H  21/0000Z 38.8N  20.8W   45 KT  50 MPH
 36H  21/1200Z 39.2N  19.3W   35 KT  40 MPH...POST-TROPICAL
 48H  22/0000Z 39.3N  18.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  23/0000Z...DISSIPATED
 
$$
FORECASTER PASCH
 
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