000
WTNT43 KNHC 200833
TCDAT3
 
HURRICANE GORDON DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012
500 AM AST MON AUG 20 2012
 
SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THE CENTER OF
THE EYE OF HURRICANE GORDON PASSED OVER SANTA MARIA ISLAND IN THE
EASTERN AZORES AROUND 0530 UTC. SINCE THAT TIME...HOWEVER...THE
CLOUD PATTERN OF THE CYCLONE HAS BECOME RAGGED AND SHEARED TO THE 
NORTHEAST OF THE EXPOSED LOW-LEVEL EYE FEATURE. THE INITIAL
INTENSITY OF 65 KT IS BASED ON A CONSENSUS SATELLITE CI-NUMBER OF
T4.0/65 KT FROM TAFB...SAB...AND UW-CIMSS ADT...WHICH COULD BE
GENEROUS.

THE INITIAL MOTION ESTIMATE IS NOW 060/13. GORDON IS ON TRACK SO
THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR
REASONING. GORDON WILL GRADUALLY MOVE AWAY FROM THE AZORES ISLANDS
TODAY...AND CONTINUE TO SLOW DOWN AND TURN TOWARD THE EAST OVER THE
NEXT 48 HOURS AS THE CYCLONE WEAKENS AND BECOMES MORE VERTICALLY
SHALLOW DUE TO STRONG SOUTHWESTERLY VERTICAL WIND SHEAR AND COLDER
WATERS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS
TRACK AND IS CLOSE TO THE CONSENSUS MODELS TV15 AND TVCA.

SURFACE OBSERVATIONS FROM THE AZORES INDICATE AMBIENT AND DEWPOINT
TEMPERATURES ARE RUNNING 19-21C...WHICH IS NOT VERY TROPICAL-LIKE.
ALSO...VERTICAL SHEAR HAS INCREASED TO MORE THAN 30 KT AND IT IS
EXPECTED TO REMAIN ABOVE THAT VALUE FOR THE NEXT SEVERAL DAYS. AS A
RESULT OF THESE VERY UNFAVORABLE DYNAMIC AND THERMODYNAMIC
CONDITIONS...GORDON IS EXPECTED TO TRANSITION INTO A POST-TROPICAL
EXTRATROPICAL CYCLONE WITHIN THE NEXT 12-24 HOURS...AND DISSIPATE
OVER THE COLD ATLANTIC WATERS BETWEEN THE AZORES AND PORTUGAL BY 72
HOURS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
ADVISORY AND CLOSELY FOLLOWS THE DECAY-SHIPS INTENSITY MODEL.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/0900Z 37.4N  24.3W   65 KT  75 MPH
 12H  20/1800Z 38.3N  22.1W   55 KT  65 MPH...POST-TROP/EXTRATROP
 24H  21/0600Z 38.9N  20.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
 36H  21/1800Z 39.2N  18.7W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  22/0600Z 39.2N  17.3W   30 KT  35 MPH...POST-TROP/EXTRATROP
 72H  23/0600Z...DISSIPATED
 
$$
FORECASTER STEWART