956
WTPZ45 KNHC 201456
TCDEP5
TROPICAL STORM KIKO DISCUSSION NUMBER 23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152007
800 AM PDT SAT OCT 20 2007
VISIBLE SATELLITE IMAGERY SHOWS THAT KIKO HAS BECOME BETTER
ORGANIZED...WITH A WELL-DEFINED CENTRAL DENSE OVERCAST ALMOST
SURROUNDED BY A SOMEWHAT RAGGED OUTER BAND. OVERSHOOTING
CONVECTIVE TOPS IN THE CDO ARE COLDER THAN -80C. SATELLITE
INTENSITY ESTIMATES FROM TAFB AND SAB ARE 55 KT...AND THAT IS THE
INITIAL INTENSITY FOR THIS ADVISORY. THE CIRRUS OUTFLOW IS FAIR TO
GOOD IN ALL DIRECTIONS EXCEPT THE WEST...WHERE IT IS POOR.
THE INITIAL MOTION REMAINS 305/4. KIKO IS CURRENTLY BEING STEERED
BY A MID-LEVEL RIDGE OVER NORTHERN MEXICO...WHICH IS FORECAST TO
WEAKEN DURING THE NEXT 24 HOURS AS A DEEP-LAYER TROUGH OVER THE
WESTERN UNITED STATES AMPLIFIES SOUTHEASTWARD. THE GUIDANCE HAS
COME INTO BETTER AGREEMENT ON THE EVOLUTION OF THE TROUGH...WITH
ALL LARGE-SCALE MODELS EXCEPT THE NOGAPS FORECASTING THE TROUGH TO
MOVE FAR ENOUGH TO THE EAST TO ALLOW RIDGING TO DEVELOP IN ITS WAKE
NORTH OF KIKO. THIS SHOULD TURN KIKO MORE WESTWARD IN THE 48-72 HR
TIME FRAME. HOWEVER...THE TRACK GUIDANCE DOES NOT TOTALLY AGREE
WITH THIS SCENARIO...AS THE GFDL AND HWRF SHOW A NORTHWARD MOTION
FOR 48 HR OR SO FOLLOWED BY A NORTHWESTWARD MOTION. THE GFDL HAS A
GOOD RECENT TRACK RECORD ON STORMS IN THIS AREA...BUT IN THIS CASE
IT MAY BE DRIVING KIKO TOO MUCH INTO THE MID-LEVEL RIDGE. THE NEW
FORECAST TRACK CALLS FOR A NORTHWESTWARD MOTION FOR THE FIRST 48
HR...FOLLOWED BY A GRADUAL TURN TOWARD THE WEST-NORTHWEST IN BEST
AGREEMENT WITH THE CCON CONSENSUS MODEL. AN ALTERNATE SCENARIO
WOULD BE A NORTHWARD TURN IN THE NEXT 12-24 HR AS THE TROUGH
APPROACHES FOLLOWED BY A SHARPER TURN TOWARD THE WEST AS THE
TRAILING RIDGE BUILDS...AS SUGGESTED BY THE GFDN. THERE REMAINS
CONSIDERABLE UNCERTAINTY IN THE TRACK FORECAST...ESPECIALLY IN
REGARDS TO HOW CLOSE KIKO MAY COME TO BAJA CALIFORNIA.
KIKO IS IN AN AREA OF LIGHT VERTICAL WIND SHEAR...AND THAT IS LIKELY
TO CONTINUE FOR THE NEXT 36 HR OR SO. ALL GUIDANCE FORECASTS
STRENGTHENING DURING THAT TIME...AND THE NEW INTENSITY FORECAST NOW
CALLS FOR KIKO TO PEAK AT 80 KT IN 36 HR. AFTER THAT TIME...
INCREASING SHEAR AND COOLING SEA SURFACE TEMPERATURES ALONG THE
FORECAST TRACK SHOULD CAUSE WEAKENING. THE SSTS ARE BELOW 24C
ALONG THE FORECAST TRACK WEST OF 110W...SO THE NEW INTENSITY
FORECAST SHOWS A FASTER WEAKENING THAN THE PREVIOUS ADVISORY.
WIND RADII HAVE BEEN REVISED BASED ON JUST-RECEIVED QUIKSCAT DATA.
FORECAST POSITIONS AND MAX WINDS
INITIAL 20/1500Z 18.1N 106.6W 55 KT
12HR VT 21/0000Z 18.7N 107.2W 65 KT
24HR VT 21/1200Z 19.6N 107.8W 75 KT
36HR VT 22/0000Z 20.4N 108.6W 80 KT
48HR VT 22/1200Z 20.8N 109.5W 75 KT
72HR VT 23/1200Z 21.5N 112.0W 65 KT
96HR VT 24/1200Z 22.0N 115.5W 45 KT
120HR VT 25/1200Z 22.5N 119.5W 30 KT
FORECASTER BEVEN
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