WDPN32 PGTW 090300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W WARNING NR 14//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 090000Z TO 130000Z SEP 2005.
   A. TYPHOON (TY) 15W (KHANUN), LOCATED APPROXIMATELY 445 NM SOUTH-
SOUTHEAST OF OKINAWA, HAS TRACKED NORTHWESTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS.
   B. TY 15W IS CURRENTLY BEING STEERED NORTHWESTWARD BY AN EQUATOR-
WARD EXTENSION OF A LARGE SUBTROPICAL RIDGE CENTERED EAST OF JAPAN.
UPPER AIR ANALYSIS INDICATES HEIGHT RISES AND EASTERLY FLOW NORTH OF
THE STORM OVER THE SOUTHERN RYUKYU ISLANDS WHICH INDICATES A TRANSI-
TION IN THE PRIMARY STEERING INFLUENCE ON TY 15W. ONCE THE STEERING 
MECHANISM SHIFTS TO THE WESTERN PERIPHERY OF THE RIDGE, THE SYSTEM
IS FORECAST TO TRACK WEST-NORTHWESTWARD. THIS MOTION WILL CONTINUE
THROUGH THE REMAINDER OF THE FORECAST PERIOD. INITIAL LANDFALL IS
FORECAST TO OCCUR OVER NORTHERN TAIWAN AROUND TAU 48, FOLLOWED BY A
SECOND LANDFALL IN SOUTHEASTERN CHINA BY TAU 72. THE DYNAMIC AIDS
CONSISTING OF COAMPS, EGRR, GFDN, GFS, JGSM, JTYM, MM5, NOGAPS,
TCLAPS, AND WBAR ARE IN GOOD AGREEMENT THROUGH 24 HOURS AND FAIR
AGREEMENT THEREAFTER.
   C. THE SYSTEM HAS MAINTAINED ITS INTENSITY OVER THE LAST 12 HOURS.
OUTFLOW ALONG THE NORTHERN PERIPHERY OF TY 15W CONTINUES TO IMPROVE,
BUT A SMALL UPPER LEVEL LOW JUST WEST OF THE SYSTEM IS LIMITING STORM
OUTFLOW IN THE SOUTHWESTERN QUADRANT. AS A RESULT, THE STORM IS FORE-
CAST TO STRENGTHEN AT A LESS THAN CLIMATOLOGICAL RATE THROUGH TAU 36.
THE SYSTEM WILL BEGIN TO WEAKEN BY TAU 48 AS SURFACE INFLOW IS DIS-
RUPTED AS THE STORM APPROACHES TAIWAN. FURTHER WEAKENING IS FORECAST
BY TAU 72 AS THE STORM MAKES A SECOND LANDFALL AND ENTRAINS CONTI-
NENTAL AIR AND BEGINS TO DISSIPATE.
   D. CURRENT WIND RADII ARE BASED ON A 082201Z SSM/I PASS. FORE-
CAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE-SIZED SYS-
TEM.
   E. TY 15W WILL TRACK INLAND OVER SOUTHEAST CHINA AND DISSIPATE BY 
TAU 96. 
3. FORECAST TEAM: DELTA//
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