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Tropical Storm KEVIN


ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM KEVIN DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP142009
200 PM PDT SAT AUG 29 2009
 
THE CYCLONE HAS DEVELOPED A CURVED BAND THAT WRAPS AROUND TO THE
WEST AND SOUTH OF THE ESTIMATED CENTER...RESULTING IN DVORAK
CI-NUMBERS OF 3.0 FROM TAFB AND 2.5 FROM SAB AND 1800 UTC. BASED ON
THIS...THE CYCLONE IS UPGRADED TO KEVIN WITH AN INITIAL INTENSITY
OF 40 KT. KEVIN IS THE SEVENTH NAMED STORM TO FORM THIS MONTH IN
THE EAST PACIFIC BASIN...THE MOST IN AUGUST SINCE 1968 AND THE MOST
IN ANY MONTH SINCE 1985.
 
RECENT SATELLITE DATA SUGGESTS THAT THE CENTER OF KEVIN IS LOCATED
FARTHER SOUTHWEST THAN PREVIOUSLY THOUGHT. THE CYCLONE IS CURRENTLY
LOCATED SOUTH OF A WEAKNESS IN THE SUBTROPICAL RIDGE...RESULTING IN
LIGHT STEERING CURRENT. AS A RESULT...THE CYCLONE HAS BEEN MOVING
VERY LITTLE OVER THE PAST SEVERAL HOURS. A LONGER-TERM INITIAL
MOTION ESTIMATE OF 285/08 WAS USED TO INITIALIZE THE GUIDANCE...AND
THE ADVISORY MOTION IS 290/04. 

THE TRACK MODEL GUIDANCE SHOWS A VERY WIDE SPREAD THROUGH THE
PERIOD. THE GFDL...HWRF...AND ALL OF THE GLOBAL MODELS EXCEPT THE
CANADIAN NOW SHOW AT LEAST SOME EASTWARD COMPONENT OF MOTION. THIS
SEEMS TO BE DUE TO INTERACTION OF KEVIN WITH HURRICANE JIMENA AND
THE STEERING INFLUENCE OF A MID- TO UPPER-LEVEL TROUGH THAT IS
CURRENTLY DIGGING SOUTHWEST FROM BAJA CALIFORNIA. THE AMOUNT OF
EASTWARD MOTION VARIES DRAMATICALLY...WITH THE UKMET...GFDL...
GFS...NOGAPS...AND ECMWF SHOWING AN EASTWARD COMPONENT OF MOTION
THROUGH DAY 5. HOWEVER...THE HWRF...GFS ENSEMBLE MEAN AND CANADIAN
SHOW A TURN TO THE WEST LATE IN THE PERIOD...IT IS DIFFICULT TO SORT
OUT THESE DIFFERENCES SINCE THE GLOBAL MODEL ANALYSES OF BOTH
JIMENA AND KEVIN SEEM TO BE TOO WEAK. ALSO...THE HWRF RUN FOR KEVIN
HAS AN UNREALISTICALLY WEAK REPRESENTATION OF JIMENA...WHICH IS THE
MUCH STRONGER CYCLONE AT THIS TIME. 

ALL THIS BEING SAID...THE OFFICIAL FORECAST TRACK HAS BEEN MODIFIED
CONSIDERABLY FROM THE PREVIOUS PACKAGE. INITIALLY...THE TRACK IS
FARTHER SOUTHWEST OF THE PREVIOUS PACKAGE DUE TO THE INITIAL
POSITION AND MOTION. LATER IN THE PERIOD...THE OFFICIAL FORECAST
TRENDS TOWARD THE MODELS THAT SHOW THE EASTWARD TURN. AFTER AN
INITIAL NORTHWEST MOTION...THE FORECAST TURNS KEVIN NORTHWARD BY 24
HOURS FOLLOWED BY A GRADUAL NORTHEASTWARD TURN AT SLOW SPEED
THROUGH DAY 4. BY DAY 5...A VERY SLOW NORTHWARD MOTION IS
INDICATED...DUE TO THE LARGE SPREAD IN THE GUIDANCE. NEEDLESS TO
SAY...THERE IS VERY LOW CONFIDENCE IN THIS TRACK FORECAST.
 
THE SHIPS AND LGEM CONTINUE TO SHOW MORE STRENGTHENING THAN THE
DYNAMICAL INTENSITY AIDS. GIVEN RECENT ORGANIZATIONAL TRENDS...THE
OFFICIAL FORECAST FOLLOWS THE STATISTICAL MODELS THROUGH 36
HOURS...SHOWING A PEAK AT 50 KT FOLLOWED BY A SLOW DECREASE LATER
IN THE PERIOD AS THE CYCLONE REACHES COOLER WATERS AND SHEAR BEGINS
TO INCREASE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/2100Z 12.8N 122.2W    40 KT
 12HR VT     30/0600Z 13.2N 122.9W    45 KT
 24HR VT     30/1800Z 14.2N 122.9W    50 KT
 36HR VT     31/0600Z 15.1N 122.7W    50 KT
 48HR VT     31/1800Z 16.1N 122.2W    45 KT
 72HR VT     01/1800Z 17.5N 121.5W    40 KT
 96HR VT     02/1800Z 18.5N 120.5W    35 KT
120HR VT     03/1800Z 19.5N 120.5W    30 KT
 
$$
FORECASTER BRENNAN
 
NNNN


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Page last modified: Thursday, 31-Dec-2009 12:09:25 UTC