WDPN32 PGTW 171500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (USAGI) WARNING NR 04// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 17W (USAGI), LOCATED APPROXIMATELY 559 NM SOUTH- SOUTHEAST OF KADENA AB, HAS TRACKED WESTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS A CONSOLIDATING AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) THAT HAS BECOME TIGHTER WRAPPED AS A CENTRAL DENSE OVERCAST FEATURE HAS STARTED TO BUILD ALONG THE SOUTHERN EDGE OF THE LLCC. A 171050Z PARTIAL TRMM MICROWAVE IMAGE SHOWS THE LLCC HAS CONTINUED TO CONSOLIDATE AND WRAP TIGHTER WHILE THE CONVECTION HAS CONTINUED TO DEEPEN. THE CURRENT INTENSITY HAS BEEN INCREASED TO 40 KNOTS WHICH IS SLIGHTLY HIGHER THAN DVORAK INTENSITY ESTIMATES OF 35 KNOTS FROM PGTW AND RJTD DUE TO THE IMPROVING ORGANIZATION OF THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES A POINT-SOURCE ANTICYCLONE HAS MOVED OVER THE LLCC WHILE A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL IS LOCATED TO THE NORTHEAST HAS STARTED TO FILL AND DISSIPATE. THIS IS OVERALL PROVIDING FAVORABLE EQUATORWARD OUTFLOW AND LOW TO MODERATE (05-15 KNOTS) VERTICAL WIND SHEAR. TS 17W IS SLOWLY TRACKING WESTWARD ALONG THE EXTREME SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE NORTH OF THE SYSTEM. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 17W IS WILL SLOWLY TRACK WESTWARD AS THE STR IS EXPECTED TO BECOME MORE ESTABLISHED TO THE NORTH OF THE SYSTEM THROUGH THE NEXT 36 HOURS. AFTER TAU 36, A MID-LATITUDE TROUGH IS EXPECTED TO DIG IN ACROSS NORTHEASTERN CHINA, WHICH WILL SLIGHTLY MODIFY THE STR ALLOWING FOR TS 17W TO TAKE A MORE NORTHWESTWARD TRACK TOWARDS SOUTHERN TAIWAN. AN OVERALL FAVORABLE ENVIRONMENT WILL CONTINUE TO ENHANCE THE DEVELOPMENT OF THE SYSTEM THROUGH TAU 72 ALLOWING FOR A PEAK INTENSITY OF 95 KNOTS. C. IN THE EXTENDED TAUS, TS 17W WILL CONTINUE TO TRACK ALONG THE SOUTHWESTERN PERIPHERY OF THE STR. LAND INTERACTION WITH TAIWAN WILL CAUSE SLOW WEAKENING AS THE SYSTEM APPROACHES THE SOUTHEASTERN COAST NEAR TAU 96. NUMERIC MODEL GUIDANCE IS IN FAIR AGREEMENT WITH THE GENERAL WESTWARD TO NORTHWESTWARD TRACK THROUGH TAU 72, BUT THERE CONTINUES TO BE VARIATIONS IN THE ORIENTATION OF STR AS TS 17W APPROACHES TAIWAN. THE CURRENT FORECAST TRACK IS LAID CLOSE TO MULTI- MODEL CONSENSUS WITH LOW, BUT IMPROVING CONFIDENCE AS THE MODELS CONTINUE TO MOVE INTO BETTER AGREEMENT WITH THE FORECAST TRACK.// NNNN