WTPA42 PHFO 260245
TCDCP2

TROPICAL STORM NEKI DISCUSSION NUMBER  30
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP032009
500 PM HST SUN OCT 25 2009

NEKI IS SLOWLY SPINNING DOWN AS IT INITIALLY MOVES WESTWARD. USING
2330 UTC IMAGERY...PHFO AND JTWC BOTH GAVE CI VALUES OF 2.5. SAB
DID THE SAME WITH 0000 UTC IMAGERY. SINCE THE LOW LEVEL CIRCULATION
CENTER CONTINUES TO MOVE FARTHER AWAY FROM DEEP CONVECTION...AND
BECAUSE THIS CENTER IS BEGINNING TO LOSE DEFINITION ALONG ITS NORTH
SIDE...INITIAL NEKI INTENSITY THIS TIME IS DECREASED TO 40 KT. THE
INITIAL NORTHEAST QUADRANT GALE RADIUS HAS BEEN DECREASED TO 165
NM...WITH THE RADIUS CONTRACTED TO 140 NM AT TAU 12...THEN MATCHED
WITH SMALLER RADII SET IN THE PREVIOUS PACKAGE FOR ALL SUBSEQUENT
TAU.
 
SINCE 0000 UTC...SATELLITE LOOP SHOWS NEKI IS MOVING ALMOST DUE WEST 
AFTER MOVING NORTHWEST DURING THE PREVIOUS 6 HOURS. INITIAL MOTION 
IS SET AT 275 DEGREES AT 5 KT...BUT THIS IS REALLY AN AVERAGE 3 HOUR 
MOTION SINCE 0000 UTC. INSTANTANEOUS 1 HOUR MOTION AT 0130 UTC WOULD 
SUGGEST A TRACK FARTHER NORTH OF DUE WEST...BUT THIS MAY BE DUE TO 
WOBBLING OR TO AN OPTICAL ILLUSION CAUSED BY THE LOSS OF DEFINITION 
ON THE NORTHERN FLANK OF THE CENTER. THE 5 KT INITIAL SPEED IS A TAD 
FASTER THAN THAT SEEN 6 HOURS AGO. 
 
THE 0000 UTC UW/CIMSS VERTICAL SHEAR PRODUCT SHOWS ABOUT 21 KT OF 
WESTERLY SHEAR...A DROP FROM ABOUT 23 KT NOTED AT 1800 UTC...AND 
FROM 31 KT NOTED AT 1200 UTC. HOWEVER THIS SHEAR...SUPPLIED BY A 
LARGE UPPER TROPOSPHERIC TROUGH LOCATED JUST WEST NORTHWEST OF 
NEKI...REMAINS STRONG ENOUGH TO BE DETRIMENTAL TO THE HEALTH OF THIS 
SYSTEM. NEKI SITS RIGHT ON THE 26 DEGREE C SST ISOTHERM...SO IT 
SEEMS CLEAR THAT NEKI WOULD NOT INTENSIFY EVEN IF IT WERE TO SIT 
STILL. IN SPITE OF CONTINUED SLOW MOVEMENT TO THE WEST...TRACK 
GUIDANCE ALMOST UNANIMOUSLY SWINGS NEKI TOWARD THE NORTH 
TONIGHT...THEN TOWARD THE NORTHEAST MONDAY AND AFTERWARD. THE 
FORECAST TRACK IS SHIFTED AGAIN TO THE LEFT FROM THE PREVIOUS 
TRACK...THIS TIME AT ALL TAU...TO RECONCILE THE CURRENT WESTERLY 
MOVEMENT WITH THE FORECAST SWING TO THE NORTH. THIS TRACK WILL TAKE 
NEKI OVER COOLER WATER AND INTO THE PATH OF INCREASING SHEAR...SO 
GRADUAL WEAKENING IS EXPECTED.
 
NEKI IS EXPECTED TO UNDERGO EXTRATROPICAL TRANSITION BEYOND 36 HOURS
AS A LARGE AMPLITUDE UPPER LEVEL TROUGH AND A STRONG SURFACE FRONT
BEGIN TO INTERACT WITH IT. THIS INTERACTION WILL ALSO CAUSE NEKI TO
ACCELERATE AS IT MOVES TOWARDS THE NORTHEAST. THE TRANSITION FROM
TROPICAL STORM TO EXTRATROPICAL GALE SHOULD BE COMPLETE BY MIDDAY
TUESDAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0300Z 25.0N 165.3W    40 KT
 12HR VT     26/1200Z 26.8N 165.5W    40 KT
 24HR VT     27/0000Z 31.0N 163.7W    35 KT
 36HR VT     27/1200Z 36.7N 160.9W    35 KT...BECOMING EXTRATROPICAL
 48HR VT     28/0000Z 43.1N 157.3W    35 KT...EXTRATROPICAL
  
$$
FORECASTER POWELL