813
WTPZ45 KNHC 200900
TCDEP5
TROPICAL STORM KIKO DISCUSSION NUMBER 22
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152007
200 AM PDT SAT OCT 20 2007
UNTIL ABOUT TWO HOURS AGO...KIKO WAS NOT PRODUCING ALL THAT MUCH
DEEP CONVECTION...BUT A HEALTHY BURST HAS RECENTLY ERUPTED OVER THE
NORTHWESTERN QUADRANT...OBSCURING THE LOW-LEVEL CENTER. SUBJECTIVE
DVORAK INTENSITY ESTIMATES AT 06Z WERE 45-55 KT...WITH OBJECTIVE
ESTIMATES FAVORING THE LOWER END OF THAT RANGE. GIVEN THE INCREASE
IN CONVECTION SINCE THEN...THE ADVISORY INTENSITY IS RAISED
SLIGHTLY TO 50 KT. THE ENVIRONMENT IS CONDUCIVE FOR
STRENGTHENING...AND ESSENTIALLY ALL OF THE INTENSITY GUIDANCE
FORECASTS KIKO TO BE NEAR HURRICANE STRENGTH IN A DAY OR TWO. THE
OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY IN CALLING
FOR KIKO TO BECOME A HURRICANE IN ABOUT 24 HOURS GIVEN THE WEAK
WIND SHEAR AND VERY WARM SSTS. THE FORECAST INTENSITY PEAKS AT 75
KT IN ABOUT 48 HOURS...WITH A GRADUAL DECLINE THEREAFTER AS SHEAR
INCREASES AND SSTS EVENTUALLY COOL BENEATH THE CYCLONE.
KIKO CONTINUES SLOWLY NORTHWESTWARD AT ABOUT 305/4...TO THE SOUTH OF
A MID-LEVEL RIDGE OVER NORTHERN MEXICO. THAT RIDGE IS FORECAST BY
ALL OF THE DYNAMICAL MODELS TO ERODE DURING THE NEXT 24 HOURS AS A
DEEP-LAYER LOW PRESSURE SYSTEM ARRIVES OVER THE WESTERN UNITED
STATES. ALL OF THE MODELS EVENTUALLY SHOW THAT SYSTEM PROCEEDING
EASTWARD...ALLOWING A RIDGE TO BUILD ALONG THE WEST COAST OF MEXICO
AND CALIFORNIA IN A FEW DAYS. IN RESPONSE TO THAT PATTERN
CHANGE...THE MODELS REMAIN EXTREMELY DIVERGENT BEYOND ABOUT 36
HOURS. THE GFDL REMAINS ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE
BUT HAS SHIFTED SLIGHTLY TO THE LEFT ON THE LATEST RUN...TAKING
KIKO NORTHWESTWARD ACROSS THE SOUTHERN TIP OF BAJA CALIFORNIA IN
48-72 HOURS. THE GFS AND ECMWF GLOBAL MODELS ARE ON THE LEFT SIDE
OF THE MODEL SPREAD...SHOWING A WESTWARD TURN WELL SOUTH OF BAJA
CALIFORNIA IN ABOUT 24 HOURS. IT IS A LITTLE DIFFICULT FOR ME TO
ANTICIPATE A WESTWARD TURN THAT SOON...GIVEN THAT KIKO SHOULD BE A
DEEP SYSTEM WITH NO SIGNIFICANT MID-LEVEL RIDGE FORECAST TO ITS
NORTH UNTIL ABOUT BEYOND 48 HOURS FROM NOW. THE NEW OFFICIAL TRACK
FORECAST LEANS A LITTLE MORE TOWARD THE GFDL SOLUTION AND IS A BIT
FASTER AND TO THE NORTH OF THE PREVIOUS FORECAST STARTING ON DAY
2...BUT IT STILL CALLS FOR KIKO TO TURN WESTWARD SOUTH OF THE
SOUTHERN TIP OF BAJA CALIFORNIA. IT IS IMPORTANT TO EMPHASIZE THAT
THIS TRACK FORECAST IS HIGHLY UNCERTAIN GIVEN THE TREMENDOUS MODEL
SPREAD.
FORECAST POSITIONS AND MAX WINDS
INITIAL 20/0900Z 17.7N 106.1W 50 KT
12HR VT 20/1800Z 18.3N 106.8W 55 KT
24HR VT 21/0600Z 19.1N 107.5W 65 KT
36HR VT 21/1800Z 19.9N 108.2W 70 KT
48HR VT 22/0600Z 20.7N 108.9W 75 KT
72HR VT 23/0600Z 21.7N 110.7W 65 KT
96HR VT 24/0600Z 22.5N 113.5W 50 KT
120HR VT 25/0600Z 23.0N 117.0W 40 KT
FORECASTER KNABB
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