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HURRICANE KENNA DISCUSSION NUMBER  12
NATIONAL WEATHER SERVICE MIAMI FL
2 PM PDT THU OCT 24 2002
 
SCORE ONE FOR THE DVORAK TECHNIQUE.  SATELLITE CLASSIFICATIONS FOR
KENNA...BOTH THE OBJECTIVE AND THE SAB SUBJECTIVE...ARE AT T7.0...OR
140 KT/921 MB.  THE TAFB ESTIMATE IS 127 KT.  ON THEIR FIRST PASS
THROUGH KENNA...THE RECONNAISSANCE AIRCRAFT REPORTED 921 MB AND A
FLIGHT-LEVEL WIND OF 145 KT.  ON THE SECOND PASS...THE DROPSONDE 
PRESSURE WAS 918 MB...BUT WITH 27 KT OF WIND AT THE SURFACE.  THE 
MINIMUM PRESSURE IS THEREFORE ESTIMATED TO BE A BIT LOWER THAN THAT. 
A DROPSONDE RELEASED IN THE SOUTHEAST QUADRANT REPORTED A PEAK WIND 
OF 189 KT...AND A MEAN WIND OVER THE LOWEST 500 M OF 172 KT.  THIS 
DROP SUPPORTS SURFACE WINDS OF ABOUT 140 KT...IN GOOD AGREEMENT WITH 
THE SATELLITE ESTIMATES.  

THE INITIAL MOTION IS 360/9.  THE TRACK HAS BEEN WELL BEHAVED SO 
FAR...AND THERE IS NO SIGNIFICANT CHANGE TO THE SYNOPTIC 
REASONING...OBJECTIVE GUIDANCE...OR FORECAST TRACK.  KENNA IS 
APPROACHING A MAJOR TROUGH IN THE WESTERLIES THAT WILL TURN
THE CYCLONE TO THE NORTHEAST OVER THE NEXT 24 HOURS.  THE GFS 
CONTINUES TO INITIALIZE A RELATIVELY WEAK VORTEX AND REMAINS ON THE 
LEFT SIDE OF THE GUIDANCE ENVELOPE.  THE OFFICIAL FORECAST REMAINS 
IN BETTER AGREEMENT WITH THE GFDL AND UKMET...WITH A LANDFALL MOST 
LIKELY BETWEEN MAZATLAN AND CABO CORRIENTES.
 
KENNA IS ROUNDING THE RIDGE AXIS...QUITE OFTEN THE LOCATION OF A 
CYCLONES PEAK INTENSITY.  A WEAKENING TREND IS LIKELY TO BEGIN SOON 
AS KENNA BEGINS TO ENCOUNTER INCREASING SOUTHWESTERLY SHEAR.  THE 
MAIN QUESTION IS HOW FAST WILL IT WEAKEN.  THE SYNOPTIC FACTORS 
WOULD NOT SUGGEST A RAPID WEAKENING...AS THE SHEAR WILL NOT BE THAT 
STRONG AND THE WATERS UNDER THE CYCLONE WILL REMAIN VERY WARM.  ON 
THE OTHER HAND...RECON AND MICROWAVE DATA INDICATE THAT KENNA HAS 
ONLY A TINY CORE OF VERY STRONG WINDS AND NOT MUCH OUTSIDE THAT 
CORE.  THIS MEANS THAT IF THE CORE COLLAPSES THEN THERE COULD BE A 
SIGNIFICANT WEAKENING PRIOR TO LANDFALL.  THE STATE OF THE SCIENCE 
SIMPLY DOES NOT ALLOW US TO BE CONFIDENT IN ASSESSING HOW THE INNER 
CORE WILL EVOLVE OVER THE NEXT 24 HOURS.  THE OFFICIAL FORECAST IS 
NECESSARILY CONSERVATIVE IN THIS REGARD.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     24/2100Z 17.8N 108.7W   140 KTS
12HR VT     25/0600Z 19.2N 108.2W   135 KTS
24HR VT     25/1800Z 21.3N 106.2W   120 KTS
36HR VT     26/0600Z 24.0N 103.0W    50 KTS...INLAND
48HR VT     26/1800Z 27.5N  99.0W    30 KTS...DISSIPATING INLAND
72HR VT     27/1800Z...DISSIPATED
 
 
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