Tropical Storm GORDON

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TROPICAL STORM GORDON DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072006
500 PM EDT MON SEP 11 2006
 
AN AIR FORCE RECONNAISSANCE AIRCRAFT HAS BEEN INVESTIGATING 
THE TROPICAL CYCLONE AND REPORTED PEAK FLIGHT LEVEL WINDS OF 47 KT
WHICH REDUCES TO 38 KT AT THE SURFACE. THUS THE SYSTEM IS BEING
UPGRADED TO TROPICAL STORM GORDON ON THIS ADVISORY WITH AN INITIAL
INTENSITY OF 40 KT. THE UPGRADE IS ALSO SUPPORTED BY DVORAK
SATELLITE INTENSITY ESTIMATES OF 35 KT FROM SAB...TAFB AND AFWA.
SINCE THE TIME OF THE FIRST AIRCRAFT FIX THE OVERALL SATELLITE
PRESENTATION HAS IMPROVED WITH INCREASING BANDING FEATURES AND
EXPANDING OUTFLOW.
 
THE INITIAL MOTION IS 310/8...SLIGHTLY FASTER AND TO THE RIGHT OF
THE PREVIOUS ADVISORY. THE TRACK GUIDANCE IS DIVIDED INTO 2
CAMPS...THE BAMS ON THE LEFT AND THE VARIOUS DYNAMICAL MODELS AND
CONSENSUS TO THE RIGHT. THE FORECAST TRACK IS ADJUSTED TO THE RIGHT
OUT OF RESPECT FOR THE DYNAMICAL GUIDANCE AND SLIGHTLY FASTER THAN
THE PREVIOUS ADVISORY BASED ON THE INITIAL MOTION. THE GLOBAL
MODELS ARE ALL IN AGREEMENT IN TURNING THE SYSTEM MORE NORTHWARD
AND HEADING FOR A BREAK IN THE SUBTROPICAL RIDGE. THE GFS IS AN
OUTLIER AND TRAPS THE SYSTEM BENEATH THE SUBTROPICAL RIDGE LATE IN
THE FORECAST. THIS SOLUTION SEEMS UNLIKELY AND IS IN PART DUE TO
POOR INITIALIZATION OF THE SYSTEM BY THAT MODEL WHICH ALSO
DISSIPATES GORDON WITHIN 72 HOURS. 
 
THE INTENSITY FORECAST IS HIGHER THAN IN THE PREVIOUS ADVISORY
GIVEN THE SYSTEM'S INITIAL INTENSITY OF 40 KT AND DECREASING
ENVIRONMENTAL SHEAR. GIVEN THE MORE CONDUCIVE CONDITIONS AND
INCREASED ORGANIZATION OF THE SYSTEM...MORE SIGNIFICANT
STRENGTHENING SEEMS LIKELY THAN PREVIOUSLY INDICATED. GORDON COULD
BECOME A HURRICANE IN A COUPLE OF DAYS. THE INTENSITY FORECAST IS
NOT QUITE AS AGGRESSIVE AS THE FSU SUPERENSEMBLE AND IS IN
REASONABLE AGREEMENT WITH SHIPS AND THE GFDL HURRICANE MODEL.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/2100Z 21.6N  57.3W    40 KT
 12HR VT     12/0600Z 22.4N  58.3W    45 KT
 24HR VT     12/1800Z 23.7N  59.3W    55 KT
 36HR VT     13/0600Z 25.0N  60.1W    60 KT
 48HR VT     13/1800Z 26.5N  60.5W    65 KT
 72HR VT     14/1800Z 29.0N  60.5W    70 KT
 96HR VT     15/1800Z 31.5N  60.0W    70 KT
120HR VT     16/1800Z 34.0N  59.5W    70 KT
 
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FORECASTER COBB/PASCH
 
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