Wdpn31 Pgtw 100300 

msgid/genadmin/navpacmetoccen Pearl Harbor hi/jtwc// 

subj/prognostic reasoning for tropical storm 23w warning nr 05//
rmks/
1. For meteorologists.
2. Prognostic reasoning for 100300z to 150300z Nov 2006.
   A. Tropical storm 23w (Chebi), located approximately 370 nm east
of Manila, Philippines, has tracked westward at 14 knots over the
past six hours.
   B. Ts 23w continues tracking westward along the southern periphery
of the subtropical ridge (str) extending from the northern marianas
to northern Vietnam. The available objective aids continue to predict
an intense midlatitude trough deepening over eastern China, and cre-
ating a break in the str by tau 36. The behavior of ts 23w in re-
sponse to the trough is highly dependent on whether the storm makes 
landfall over Luzon prior to the breakdown of the steering ridge. At 
its current speed, ts 23w will landfall and weaken prior to tau 36, 
and then be steered southwestward by a lower-level anticyclone anch-
ored over Vietnam. The available dynamic aids with the exception of
WBAR and EGRR are in general agreement with this scenario. In an
alternate scenario presented by EGRR and WBAR, ts 23w slows signif-
icantly prior to landfall, and then slowly tracks northward toward
the break in the subtropical ridge. This solution seems less likely
due to the current speed of ts 23w and strength of the str. This
forecast is based on a consensus of the available dynamic aids with
less emphasis on EGRR and WBAR. 
   C. Ts 23w has slowly intensified as better radial outflow has 
developed due to the position of the upper-level anticyclone located
just to the east of the center. A 091654z AMSR-E pass reveals a 
banding eye with surrounding deep convection. Intensification at a
slightly higher than climatological rate is forecast through tau 24
due to excellent outflow. The storm will weaken upon making landfall
over Luzon, and will further weaken in the South China Sea after tau
48 as a much colder air is entrained into the system due to a cold
surge off the asian continent behind the midlatitude trough.  
   D. Current wind radii are based on the 091654z AMSR-E pass. Fore-
cast wind radii are based on climatology for an average-sized system.
   E. In the extended Taus, ts 23w will continue to track southwest-
Ward in strong low-level northeasterly flow off the coast of Asia, 
and will continue to weaken due to drier air entrainment and 
increased vertical wind shear.
Forecast team: Bravo//
nnnn