WTPA42 PHFO 182125
TCDCP2

TROPICAL DEPRESSION THREE-C DISCUSSION NUMBER   1
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP032009
1100 AM HST SUN OCT 18 2009

TROPICAL DEPRESSION THREE-C HAS FORMED SOUTH OF THE MAIN HAWAIIAN
ISLANDS. OVERNIGHT...A LOW IN THE NEAR EQUATORIAL TROUGH HAD BECOME
BETTER ORGANIZED...BUT SATELLITE IMAGERY SHOWED NO CLEARCUT LOW
LEVEL CENTER AND CONVECTION WAS MAINLY AROUND THE FRINGE OF THE
LARGE CIRCULATION.

EARLY THIS MORNING...VISIBLE SATELLITE IMAGERY SHOWED A
WELL-ORGANIZED LOW LEVEL CIRCULATION CENTER WITH A LARGE AREA OF
ACTIVE CONVECTION JUST NORTHWEST OF THE CENTER. TROPICAL CYCLONES
THAT FORM WITHIN LARGE...PRE-EXISTING CIRCULATIONS OFTEN DEVELOP
RAPIDLY ONCE CONVECTION FORMS NEAR THE CENTER. THAT WAS THE CASE
WITH THREE-C.

THE DISTURBANCE THAT BECAME THREE-C HAD BEEN MOVING TOWARD THE WEST
SOUTHWEST...STEERED BY DEEP EAST NORTHEAST FLOW ON THE SOUTH SIDE
OF THE SUBTROPICAL RIDGE. HOWEVER...A STRONG TROUGH ALOFT AND AN
ASSOCIATED SURFACE FRONT NEAR MIDWAY ARE DIGGING SOUTHEAST. THE
MEAN FLOW AHEAD OF THE DIGGING TROUGH WILL VEER TO SOUTHEAST AND
STEER THREE-C ON A TRACK TOWARD THE WEST NORTHWEST GRADUALLY
CURVING TOWARD THE NORTHWEST. THE TRACK GUIDANCE IS IN GOOD
AGREEMENT ON SUCH A TRACK THROUGH 96 HOURS. OUR FORECAST TRACK IS
DOWN THE MIDDLE OF THE ENVELOPE OF THE FAVORED TRACK MODEL
GUIDANCE. AFTER 96 HOURS...AS THE TROUGH ALOFT MOVES OFF TO THE
EAST...THREE-C WILL TURN BACK TOWARD THE WEST NORTHWEST.

THREE-C IS OVER 83 DEGREE F WATER...WHICH SHOULD BE AMPLE TO SUPPORT
DEVELOPMENT...AND THERE WILL BE LITTLE CHANGE OVER THE NEXT FOUR
DAYS ALONG OUR FORECAST TRACK. THE SHIPS MODEL IS FORECASTING
MODEST SHEAR...WITH A MAXIMUM OF 16 KT FROM THE ENE OVER THE NEXT
48 HOURS...AND SHOWS SHEAR DECREASING AFTER THAT. WE SEE NO REASON
WHY THREE-C WILL NOT INTENSIFY STEADILY FOR THE NEXT FOUR DAYS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      18/2100Z  8.6N 154.7W    25 KT
 12HR VT     19/0600Z  9.3N 156.6W    30 KT
 24HR VT     19/1800Z 10.7N 159.2W    35 KT
 36HR VT     20/0600Z 12.1N 162.0W    45 KT
 48HR VT     20/1800Z 13.2N 163.8W    55 KT
 72HR VT     21/1800Z 15.4N 166.3W    60 KT
 96HR VT     22/1800Z 17.4N 167.8W    70 KT
120HR VT     23/1800Z 19.1N 169.6W    75 KT
 
$$
FORECASTER DONALDSON