WTPA42 PHFO 252059
TCDCP2

TROPICAL STORM NEKI DISCUSSION NUMBER  29
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP032009
1100 AM HST SUN OCT 25 2009

NEKI MANAGES TO HANG ON IN THE FACE OF UNFRIENDLY VERTICAL SHEAR AND
SPUTTERING DEEP CONVECTION THIS MORNING. USING 1730 UTC
IMAGERY...PHFO AND JTWC GAVE CI VALUES FOR NEKI OF 3.0 AND
2.5...RESPECTIVELY. A 1630 UTC SCATTEROMETER PASS SHOWS A SMALL 45
KT WIND PATCH WITHIN THE NORTHEAST QUADRANT...ABOUT 50 NM OUT. A
LARGER 45 KT PATCH OF WINDS LIES 145 TO 180 NM NORTHEAST OF CENTER.
INITIAL NEKI INTENSITY IS THEREFORE SET AT 45 KT. THE 45 KT WIND
PATCH FARTHER FROM THE CENTER MAY BE GRADIENT WIND NOT DIRECTLY
ASSOCIATED WITH THE SYSTEM MAX WIND BAND...BUT THE INITIAL
NORTHEAST QUADRANT GALE RADIUS HAS BEEN EXTENDED TO 180 NM. THIS
RADIUS CONTRACTS TO 140 NM AT TAU 12...THEN MATCHES SMALLER RADII
SET IN THE PREVIOUS PACKAGE FOR ALL SUBSEQUENT TAU.  

FIRST VISIBLE IMAGERY SHOWS THE LOW LEVEL CIRCULATION CENTER OF NEKI
EMERGING FROM DEEP CONVECTION TO THE EAST NORTHEAST. IT REMAINS
RATHER UNCLEAR WHETHER THIS CENTER MOVED AT ALL OVER THE PAST 6
HOURS OR SO...BUT IMAGES SINCE 1800 UTC HINT AT A SLOW DRIFT TO THE
WEST NORTHWEST. INITIAL MOTION IS THEREFORE SET AT 290 DEGREES AT 2
KT.

THE 1800 UTC UW/CIMSS VERTICAL SHEAR PRODUCT SHOWS ABOUT 23 KT OF
WESTERLY SHEAR...A DROP FROM ABOUT 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 IT WERE TO SIT STILL. TRACK GUIDANCE CONTINUES TO
SWING NEKI TOWARD THE NORTH LATER TODAY...THEN TOWARD THE NORTHEAST
TONIGHT AND AFTERWARD. THE FORECAST TRACK BEYOND 24 HOURS IS
UNCHANGED FROM THE LAST PACKAGE...WITH TAU 3 AND 12 FORECAST
POSITIONS ALTERED SLIGHTLY TO THE LEFT TO RECONCILE THE CURRENT
WESTERLY DRIFT 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.

THE TROPICAL LIFE OF THIS SYSTEM MAY BE A SHORT 48 HOURS. 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 LOW TO EXTRATROPICAL GALE SHOULD BE COMPLETE BY EARLY
TUESDAY MORNING. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      25/2100Z 24.8N 164.9W    45 KT
 12HR VT     26/0600Z 26.0N 165.2W    40 KT
 24HR VT     26/1800Z 28.9N 164.3W    35 KT
 36HR VT     27/0600Z 33.7N 162.2W    35 KT...BECOMING EXTRATROPICAL
 48HR VT     27/1800Z 40.5N 158.6W    35 KT...EXTRATROPICAL
  
$$
FORECASTER POWELL