WDPN31 PGTW 190900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SANBA) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.9N 108.4E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 155 NM EAST-SOUTHEAST OF HANOI, VIETNAM MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 13 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 16W (SANBA) HAVING A MOSTLY EXPOSED LOW LEVEL CIRCULATION (LLC) WITH PERSISTENT, CENTRALIZED FLARING CONVENTION OVER THE PAST SIX HOURS. UPPER AND MID-LEVEL CLOUDS HAVE ALMOST ENTIRELY BEEN SHEARED NORTHWARD, SHOWING EVIDENCE THE DEEP-LAYER SOUTHERLY FLOW ON THE WESTERN PERIPHERY OF THE RIDGING TO THE EAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS BEGUN TO GREATLY INFLUENCE THE SYSTEM. THE LLC IS DISCERNABLE ON A 090600Z HIMAWARI-9 VISIBLE 1KM IMAGE, WITH SHEARED CLOUDS OBSCURING THE LLCC AND NORTHERN CARDINAL QUADRANT. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A 090600Z HIMAWARI-9 VISIBLE 1KM IMAGE. THE INITIAL INTENSITY OF 35 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW, AS WELL AS SURFACE OBSERVATIONS REPORTING 30 KNOTS SOUTHEASTERLY WINDS EAST OF THE LLCC AT HAIKOU AND A SHIP OBSERVATION WEST OF THE LLCC REPORTING 39 KNOTS NORTH-NORTHEASTERLY WINDS AT 190600Z. INITIAL WIND RADII BASIS: PERSISTENCE AND SURFACE OBSERVATIONS CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS KNES: T2.5 - 35 KTS DEMS: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 190600Z CIMSS ADT: 45 KTS AT 190600Z CIMSS AIDT: 40 KTS AT 190600Z CIMSS DPRINT: 35 KTS AT 190600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 28-29 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 16W HAS EVIDENTLY ENCOUNTERED THE DEEP SOUTHERLY FLOW OF THE RIDGE TO THE EAST AND LOST MUCH OF THE MID AND UPPER LEVEL SUPPORT IT ONCE HAD, AS DISCUSSED IN THE AFOREMENTIONED. VERTICAL WIND SHEAR IS FORECAST TO STRENGTHEN OVER THE NEXT 48 HOURS AND SSTS ARE EXPECTED TO COOL AS UPWELLING OCCURS DUE TO SLOWER TRACK SPEEDS. AS A SHALLOW-TO-MEDIUM DEPTH SYSTEM, THIS WILL DISSIPATE THE STRUCTURE RATHER RAPIDLY. COMPLETE DISSIPATION IS EXPECTED PRIOR TO TAU 72. MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THAT TS 16W WILL CONTINUE TRACKING NORTH-NORTHEASTWARD THROUGH TAU 12, SLOWING DOWN TRACK SPEED THROUGH TAU 18 AND TURN BACK ON A NEAR RECIPROCAL HEADING BY TAU 24 TO TRACK SOUTH-SOUTHWEST THROUGH TAU 72. UPON SLOWING DOWN, SSTS ARE EXPECTED TO DECREASE AS UPWELLING SETS IN DUE TO REMAINING NEAR QUASI-STATIONARY FROM TAU 12 TO 24. VWS HAS INCREASED SLIGHTLY AND IS PROJECTED TO CONTINUE TO INCREASE THROUGH TAU 48 IN STATISTICAL-DYNAMICAL INTENSITY GUIDANCE. THOUGH THE SAME GENERAL PATTERN IS OBSERVED ACROSS JTWC CONSENSUS MEMBERS, THE ALONG-TRACK SPREAD DIFFERS AMONG THE MEMBERS AND IS GREATEST (307NM) BETWEEN THE GALWEM AND ECMWF SOLUTIONS. OF NOTE, THE MOGREPS SOLUTION IS CONSIDERABLE DIFFERENT FROM OTHER CONSENSUS MEMBERS, TAKING A SIMILAR TRACK AS DESCRIBED ABOVE UNTIL TAU 36 AND THEN PROMPTLY TURNING TO A NORTHWESTWARD TRACK THROUGH TAU 72. THE AMBIGUITY PRESENTED CONTRIBUTES TO AN OVERALL FORECAST CONFIDENCE OF MEDIUM. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN