WDPN32 PGTW 080300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 080000Z TO 130000Z SEP 2005.
   A. TROPICAL STORM (TS) 15W (KHANUN), LOCATED APPROXIMATELY 700 NM
SOUTH-SOUTHEAST OF OKINAWA, HAS TRACKED NORTHWESTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS.
   B. TS 15W IS BEING STEERED BY A SOUTHWARD EXTENSION OF THE LARGE
SUBTROPICAL RIDGE CENTERED EAST OF JAPAN. THE STORM IS FORECAST TO
REMAIN ON THE WESTERN PERIPHERY OF THIS STEERING RIDGE EXTENSION AND
TRACK NORTHWESTWARD THROUGH TAU 24. BETWEEN TAU 24 AND 36 THE STEERING
MECHANISM SHIFTS TO THE SECTION OF THE RIDGE THAT EXTENDS WESTWARD
INTO CHINA CAUSING THE SYSTEM TO TRACK IN A WESTWARD DIRECTION. ONCE
TS 15W SHIFTS TO THE WESTERN PORTION OF THE RIDGE, IT WILL ACCELERATE
AND IS EXPECTED TO MAKE LANDFALL OVER TAIWAN NEAR TAU 72. THE DYNAMIC
AIDS CONSISTING OF COAMPS, EGRR, GFDN, GFS, JGSM, JTYM, MM5, NOGAPS,
TCLAPS, AND WBAR ARE IN FAIR AGREEMENT THROUGH TAU 48 AND POOR AGREE-
MENT AFTER TAU 48. THIS FORECAST IS BASED ON A CONSENSUS OF ALL
AVAILABLE DYNAMIC AIDS, WITH LESS EMPHASIS PLACED ON THE EQUATORWARD
GFS OUTLIER.
   C. TS 15W IS FORECAST TO INTENSIFY AT A LESS THAN CLIMATOLOGICAL
RATE THROUGH TAU 24. WHILE THE SYSTEM IS FORECAST TO REMAIN IN A
LOW TO MODERATE VERTICAL WIND SHEAR ENVIRONMENT, UPPER LEVEL CON-
VERGENCE ASSOCIATED WITH TUTT CELLS LOCATED TO THE NORTHEAST AND
WEST OF THE STORM WILL CONTINUE TO INHIBIT STORM OUTFLOW IN THE
SHORT TERM. A GREATER RATE OF INTENSIFICATION IS FORECAST AFTER
TAU 24 AS THE INFLUENCE OF THESE TUTT CELLS DIMINISHES AND STORM
OUTFLOW IMPROVES. DEVELOPMENT OF AN EASTWARD OUTFLOW CHANNEL IS
POSSIBLE BETWEEN 36 AND 72 HOURS AS A LARGE TUTT CELL NOW WEST OF
WAKE ISLAND CONTINUES TO MOVE TOWARD THE SOUTHWEST. THIS SCENARIO
MUST BE MONITORED AS A MECHANISNM TO ENHANCE STORM INTENSIFICATION
RATES IN THE MIDDLE PERIODS.    
   D. CURRENT WIND RADII ARE BASED ON A 072032Z QUIKSCAT PASS AND
A 072216Z SSM/I PASS. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY
FOR AN AVERAGE-SIZED SYSTEM.
   E. IN THE EXTENDED PERIOD, TS 15W SHOULD CONTINUE ON A WEST-
NORTHWEST TRACK ACROSS TAIWAN AND INTO SOUTHEASTERN CHINA UNDER THE
INFLUENCE OF THE ZONAL SUBTROPICAL RIDGE AXIS. THE STORM WILL WEAKEN
INITIALLY DUE TO LANDFALL WITH TAIWAN AND AS DRIER CONTINENTAL AIR
ADVECTS INTO THE SYSTEM. A SECOND LANDFALL IN CHINA WILL FURTHER 
DISRUPT SURFACE INFLOW AND THE SYSTEM WILL RAPIDLY WEAKEN. THE STORM
WILL BE DISSIPATING OVER LAND BY TAU 120.
3. FORECAST TEAM: DELTA//
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