WDPN31 PGTW 251500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 251200Z TO 271200Z SEP 2005.
   A. TYPHOON (TY) 17W (DAMREY) IS LOCATED APPROXIMATELY 135 NM EAST
OF HAINAN, CHINA AND HAS TRACKED WESTWARD AT 06 KNOTS OVER THE PAST
SIX HOURS.
   B. TY 17W IS TRACKING TOWARD THE WEST ALONG THE SOUTHERN PERIPHERY
OF A MIDLATITUDE STEERING RIDGE CENTERED EAST OF TAIWAN. THIS RIDGE
WILL BUILD WESTWARD THROUGH TAU 72, THEREBY MAINTAINING A WEST TO
WEST-NORTHWEST TRACK THROUGH THE FORECAST PERIOD. THE STORM WILL MAKE
AN INITIAL LANDFALL ON HAINAN ISLAND WITHIN 12 HOURS AND EMERGE IN
THE GULF OF TONKIN BY TAU 24. A SECOND LANDFALL WILL OCCUR IN
NORTHERN VIETNAM AFTER TAU 36. THE DYNAMIC AIDS CONSISTING OF NOGAPS,
EGRR, WBAR, NCEP GFS, GFDN, JTYM, JGSM, COAMPS, TCLAPS AND AFWA MM5
ARE IN FAIR AGREEMENT WITH THIS SCENARIO. THIS FORECAST IS BASED ON A
CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS WITH LESS EMPHASIS PLACED ON
WBAR, THE POLEWARD OUTLIER.
   C. THE STORM WILL WEAKEN THROUGHOUT THE FORECAST PERIOD AS THE
LOW-LEVEL INFLOW BECOMES DISRUPTED BY HAINAN ISLAND AND AS CONTIN-
ENTAL AIR IS DRAWN INTO THE SYSTEM. FINAL DISSIPATION WILL OCCUR OVER
LAOS BY TAU 72.
   D. CURRENT WIND RADII ARE BASED ON 251200Z SYNOPTIC OBSERVATIONS
AND A 251040Z AMSU-B SATELLITE PASS. FORECAST WIND RADII ARE BASED ON
CLIMATOLOGY FOR AN AVERAGE-SIZED SYSTEM.
3. FORECAST TEAM: BRAVO//
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