WDPN31 PGTW 130300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W WARNING NR 03//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 130000Z TO 180000Z AUG 2006.
   A. TROPICAL STORM (TS) 11W (NONAME), LOCATED APPROXIMATELY 130 NM
WEST-NORTHWEST OF IWO JIMA, HAS TRACKED NORTHWESTWARD AT 15 KTS OVER
THE PAST SIX HOURS.
   B. TS 11W CONTINUES TO TRACK NORTHWESTWARD TOWARD A MID-LEVEL
TROUGH CREATING A BREAK IN THE SUBTROPICAL RIDGE. IT HAS CONTINUED TO
MAINTAIN ITS TRANSIT SPEED OVER THE LAST 12 HOURS AND IS EXPECTED
TO MAINTAIN SPEED AND DIRECTION OVER THE NEXT 24 HOURS. BEYOND TAU 24
THE SYSTEM WILL CONTINUE TO TRACK TOWARD SHIKOKU AND WILL SLOW AS IT
TRACKS INTO A WEAKER STEERING ENVIRONMENT. AS TS 11W TRANSITS OVER
SHIKOKU AND THE SOUTHERN TIP OF HONSHU, FURTHER REDUCTION IN SPEED IS
EXPECTED. THE INFLUENCE OF A LONGWAVE TROUGH CURRENTLY LOCATED OVER
MONGOLIA, EXTENDING INTO WESTERN CHINA, IS EXPECTED TO CAUSE TS 11W TO
TURN NORTHWARD INTO THE SEA OF JAPAN AROUND TAU 48 AND BEGIN TO TRACK
NORTHEASTWARD AT TAU 72. THE AVAILABLE DYNAMIC AIDS CONSISTING OF NCEP
GFS, GFDN, JTYM, NGPS, WBAR, EGRR, AND ECMWF ARE IN FAIR AGREEMENT
WITH A NORTH-WESTWARD TRACK THROUGH TAU 72, HOWEVER THEY HAVE BEEN
CONSISTENTLY SLOW WITH TRACK SPEED OVER THE PAST 12 HOURS. JGSM IS THE
OUTLIER WITH A STRONG TURN TO THE NORTHEAST BY TAU 12 AND A
RECURVATURE TO THE NORTHWEST AT TAU 48. THE CURRENT FORECAST IS BASED
ON A CONSENSUS OF THE AVAILABLE AIDS, WITH GREATER EMPHASIS PLACED ON
PERSISTENCE OF TRACK SPEED, AND LESS EMPHASIS ON THE JGSM TRACKER FOR
DIRECTION. 
   C. THE SYSTEM IS FORECAST TO INTENSIFY THROUGH TAU 36AT A CLIMA-
TOLOGICAL RATE DUE TO DEVELOPING FAVORABLE POLEWARD AND EQUATORWARD
OUTFLOW. VERTICAL WIND SHEAR IS EXPECTED TO REMAIN LOW AS IT AP-
PROACHES JAPAN, BUT WILL INCREASE AS TS 11W CROSSES JAPAN INTO THE
SEA OF JAPAN AROUND TAU 48. BEYOND TAU 48 TS 11W IS EXPECTED TO 
DECREASE IN INTENSITY DUE TO LAND INFLUENCES WITH JAPAN AND UNFAVOR-
ABLE SEA SURFACE TEMPERATURES (SSTS).
   D. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE
SIZED SYSTEM.
   E. IN THE EXTENDED FORECAST, THE SYSTEM WILL CONTINUE TO MOVE INTO
THE SEA OF JAPAN AND RAPIDLY WEAKEN AS IT MOVES INTO AN AREA OF HIGHER
VERTICAL WIND SHEAR AND UNFAVORABLE SSTS.
FORECAST TEAM: BRAVO//
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