MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (CHOI-WAN) WARNING NR 06// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 23W (CHOI-WAN), LOCATED APPROXIMATELY 238 NM WEST OF WAKE ISLAND, HAS TRACKED WEST-NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY CONTINUES TO SHOW DEEP CONVECTIVE BANDING WRAPPING INTO THE CENTROID. A 031619Z SSMI MICROWAVE IMAGE REVEALS THE BULK OF THE DEEP CONVECTION ARE OVER THE NORTHEAST AND SOUTHWEST QUADRANTS. DUE TO MULTIPLE MESOVORTICES ROTATING CYCLONICALLY ABOUT THE CENTROID, THE CURRENT POSITION IS BASED ON THE EIR LOOP AND SATELLITE FIXES FROM PGTW AND RJTD WITH LOW CONFIDENCE. THE SYSTEM HAS SLOWED DOWN OVER THE PAST SIX HOURS INDICATING POSSIBLE CONSOLIDATION. ALTHOUGH TS 23W IS STILL A VERY LARGE SYSTEM, IT IS GAINING CHARACTERISTICS TYPICAL OF A TROPICAL STORM, I.E., MORE CENTRALIZED DEEP CONVECTION AND A CONTRACTING WIND FIELD. THE INITIAL INTENSITY OF 40 KNOTS IS BASED ON RECENT ASCAT DATA AND CURRENT STRUCTURE. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH GOOD OUTFLOW AND LOW VWS. ADDITIONALLY, WARM SSTS ARE CONDUCIVE FOR DEVELOPMENT. TS 23W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 23W WILL CONTINUE TRACKING WESTWARD UNDER THE INFLUENCE OF THE STR. FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST; HOWEVER, DUE TO THE BROAD NATURE OF THE SYSTEM, TS 23W IS EXPECTED TO GRADUALLY INTENSIFY, LEADING TO A PEAK INTENSITY OF 85 KNOTS BY TAU 72. C. IN THE EXTENDED TAUS, TS CHOI-WAN WILL BEGIN TO ROUND THE STR AND TRACK MORE POLEWARD. AS IT GAINS LATITUDE, VWS WILL INCREASE AND SSTS WILL DECREASE, RESULTING IN GRADUAL THEN RAPID WEAKENING. CONCURRENTLY, TS 23W WILL COMMENCE EXTRA-TROPICAL TRANSITION AS IT ENTERS THE COLD BAROCLINIC ZONE. THE CYCLONE WILL TRANSFORM INTO A COLD CORE LOW BY TAU 120. AVAILABLE MODEL GUIDANCE IS IN GOOD AGREEMENT, HOWEVER, GIVEN THE UNCERTAINTY IN THE CURRENT STORM MOTION AND THE INITIAL PORTION OF THE FORECAST TRACK, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN