Tropical Storm GORDON

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TROPICAL STORM GORDON DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082012
500 PM AST FRI AUG 17 2012
 
THE SATELLITE PRESENTATION OF GORDON HAS IMPROVED SINCE THE LAST
ADVISORY.  THE CENTER OF CIRCULATION IS NOW EMBEDDED BENEATH A
CENTRAL DENSE OVERCAST WITH A BAND OF CONVECTION CURLING AROUND TO
THE EAST.  DVORAK ESTIMATES HAVE INCREASED FROM THIS MORNING...AND
THEY ARE NOW MORE SUPPORTIVE OF THE 55-KT INITIAL INTENSITY.  THE
WIND RADII HAVE BEEN INCREASED A BIT BASED ON AMSU DATA FROM
EARLIER IN THE DAY.
 
GORDON IS FULLY EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES...MOVING
EASTWARD WITH A MOTION OF 095/17 KT.  THE CYCLONE IS EXPECTED TO
CONTINUE MOVING QUICKLY EASTWARD THROUGH 72 HOURS AS IT MOVES INTO
THE BASE OF AN AMPLIFIED TROUGH OVER THE NORTHEASTERN ATLANTIC. 
AFTER THAT...GORDON SHOULD BE A WEAKER CYCLONE...AND IT WILL LIKELY
TURN EAST-SOUTHEASTWARD BY DAY 5 AS IT BECOMES STEERED BY
LOWER-LEVEL NORTHERLY FLOW.  THE TRACK GUIDANCE IS TIGHTLY
CLUSTERED THROUGH MUCH OF THE FORECAST PERIOD...ESPECIALLY WITHIN
THE FIRST 72 HOURS AS THE CYCLONE APPROACHES THE AZORES.  THE
OFFICIAL NHC TRACK FORECAST LIES BETWEEN THE GFS AND ECMWF
SOLUTIONS AND IS A LITTLE FASTER THAN THE HFIP MULTI-MODEL
CONSENSUS TV15.
 
THE VERTICAL SHEAR IS NOT EXPECTED TO BE TOO DETRIMENTAL FOR SOME
STRENGTHENING WHILE GORDON REMAINS OVER WATERS WARMER THAN 26C FOR
THE NEXT 36 HOURS OR SO.  THE DEEP-LAYER SHEAR IS EXPECTED TO
INCREASE ABOVE 30 KT BY 48 HOURS...AND WEAKENING SHOULD HAVE
COMMENCED BY THAT TIME.  GORDON SHOULD THEN COMPLETE EXTRATROPICAL
TRANSITION IN ABOUT 72 HOURS...AFTER IT HAS ALREADY PASSED THE
AZORES.  THERE IS SOME UNCERTAINTY IN THE INTENSITY FORECAST DURING
THE FIRST 48 HOURS...WITH MANY OF THE DYNAMICAL MODELS MAKING
GORDON A HURRICANE WHILE THE STATISTICAL SHIPS AND LGEM MODELS SHOW
VERY LITTLE STRENGTHENING.  THE OFFICIAL INTENSITY FORECAST BRINGS
GORDON JUST BELOW HURRICANE STRENGTH...BUT IT WOULD NOT BE
SURPRISING IF IT DID BECOME A HURRICANE DURING THE NEXT DAY OR SO.
IN FACT...BASED ON PAST NHC INTENSITY ERRORS...THERE IS A 1 IN 3
CHANCE THAT GORDON COULD BE A HURRICANE AT THE 24- AND 36-HOUR
FORECAST PERIODS.
 
BASED ON THE NEW FORECAST...GORDON WILL BE APPROACHING THE AZORES AS
A TROPICAL CYCLONE IN 48 HOURS.  THE GOVERNMENT OF PORTUGAL HAS
THEREFORE ISSUED A TROPICAL STORM WATCH FOR THE CENTRAL AND EASTERN
AZORES.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/2100Z 34.3N  44.0W   55 KT  65 MPH
 12H  18/0600Z 34.1N  41.2W   55 KT  65 MPH
 24H  18/1800Z 34.2N  37.3W   60 KT  70 MPH
 36H  19/0600Z 34.7N  33.0W   60 KT  70 MPH
 48H  19/1800Z 35.8N  28.9W   55 KT  65 MPH
 72H  20/1800Z 38.5N  21.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  21/1800Z 39.5N  17.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  22/1800Z 38.5N  14.0W   25 KT  30 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG/AVILA
 
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