WDPN31 PGTW 130300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W WARNING NR 17//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 130000Z TO 170000Z NOV 2006.
   A. TROPICAL STORM (TS) 23W (CHEBI), LOCATED APPROXIMATELY 550 NM 
SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT
07 KNOTS OVER THE PAST SIX HOURS. AS TS 23W DECREASED INTENSITY
OVER THE PAST 12 HOURS, IT HAS STARTED TO STEER IN THE LOW- TO
MID-TROPOSPHERE ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) CENTERED SLIGHTLY EAST OF TAIWAN.
   B. THROUGH TAU 48, TS 23W WILL TRACK WEST-NORTHWESTWARD TOWARDS
A WEAKNESS IN THE STR CURRENTLY LOCATED NEAR HAINAN ISLAND, CHINA. 
THIS WEAKNESS WILL BE ENHANCED BY AN APPROACHING MIDLATITUDE TROUGH
EVIDENT IN RECENT WATER VAPOR IMAGERY. AROUND TAU 72, THE WEAKENING
SYSTEM WILL TRANSITION TO A LOWER STEERING LAYER AND BEGIN TRACKING
MORE NORTHWARD. THIS SCENARIO IS SUPPORTED BY THE AVAILABLE DYNAMIC
AIDS, WHICH ARE IN GOOD AGREEMENT THROUGH TAU 48. AFTER TAU 48,
GREATER UNCERTAINTY EXISTS WITH TCLAPS FORECASTING A WESTWARD TRACK,
NOGAPS RECURVING NORTHEASTWARD, AND THE REMAINING AIDS IN BETWEEN.
   C. TS 23W WILL CONTINUE TO WEAKEN SLOWLY THROUGHOUT THE FORECAST
PERIOD DUE TO ENTRAINMENT OF DRIER AIR. FROM TAU 48, INCREASED
VERTICAL WIND SHEAR AND INTERACTION WITH LAND WILL CAUSE THE SYSTEM
TO BEGIN DISSIPATING.
   D. CURRENT WIND RADII ARE BASED ON A 122239Z QUIKSCAT IMAGE.
FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR A SMALL-SIZED
SYSTEM.
   E. AFTER TAU 72, THE DISSIPATING SYSTEM WILL BE STEERED BY
SOUTHERLY LOW-LEVEL FLOW. THE AVAILABLE DYNAMIC AIDS ARE IN POOR
AGREEMENT FROM TAU 72, WITH THE MAJORITY APPEARING TO LOSE THE
WEAKENING VORTEX. THE EXTENDED FORECAST TRACK IS BASED ON THE
850 TO 700 MB FLOW AND THE BETA ADVECTION MODELS.
FORECAST TEAM: CHARLIE//
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