WDPN32 PGTW 080900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (PODUL) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 20.6N 145.1E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 414 NM NORTH OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 13 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) AND A SMALL REGION OF FLARING CONVECTION POSITIONED JUST TO THE SOUTH OF THE ASSESSED LLCC. THE LLCC WAS PREVIOUSLY FULLY EXPOSED FOR MOST OF THE DAY, HAVING ONLY RECENTLY MADE ANOTHER ATTEMPT TO TUCK UNDER THE FLARING CONVECTION JUST PRIOR TO THE 0600Z HOUR. HOWEVER, JUST LIKE THE EARLIER ATTEMPTS, THE PRESENCE OF PERSISTENT, MODERATE NORTHEASTERLY SHEAR AND SOME DRY MID-LEVEL AIR IN THE NORTHERN FLANK, IS INHIBITING UPSHEAR CONVECTIVE DEVELOPMENT AND HENCE THE VORTEX CANNOT VERTICALLY ALIGN. A 080355Z AMSR2 37GHZ MICROWAVE IMAGE SHOWED SHALLOW BANDING FEATURES TO THE NORTH, WITH MORE ROBUST CONVECTIVE BANDS TO THE SOUTH, WRAPPING INTO A SMALL BUT DEFINED LLCC. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY OBSCURED LLCC IN THE MSI. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN AVERAGING OF THE AVAILABLE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED ABOVE AND PERSISTENCE WITH EARLIER ASCAT DATA. ENVIRONMENTAL CONDITIONS ARE FAVORABLE IN THE AGGREGATE, WITH LOW DEEP-LAYER VWS AND WARM SSTS. ANIMATED WATER VAPOR IMAGERY CONTINUES TO SHOW A WEAK TUTT-CELL POSITIONED ABOUT 450NM WEST OF TS 16W, BUT OUTFLOW REMAINS RELATIVELY WEAK TOWARDS THE EQUATOR AND SOME VERY WEAK WESTWARD OUTFLOW TOWARDS THE TUTT-CELL. INITIAL WIND RADII BASIS: RELATIVELY DRIER MID-LEVEL AIR DRAPED AROSS THE NORTHERN FLANK OF THE SYSTEM. CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 072300ZZ CIMSS ADT: 35 KTS AT 080530Z CIMSS AIDT: 37 KTS AT 080530Z CIMSS D-MINT: 30 KTS AT 080632Z CIMSS D-PRINT: 30 KTS AT 080700Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL STORM (TS) 16W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD ALONG THE SOUTHWEST SIDE OF THE STEERING RIDGE POSITIONED TO THE NORTHEAST FOR THE NEXT 24 HOURS. AFTER TAU 24, THE RIDGE WILL BUILD SOUTHWESTWARD AND MERGE WITH A WEAKER RIDGE CENTER NEAR OKINAWA, CREATING AN EXTENSIVE RIDGING COMPLEX THAT WILL EXTEND FROM COASTAL CHINA TO NEAR THE DATELINE. TS 16W WILL GRADUALLY TURN TO A WESTWARD TRACK TAU 36, TRAVELING WEST ALONG THE SOUTHERN SIDE OF THIS RIDGE PATTERN THROUGH TAU 72. AFTER TAU 48, THE SYSTEM REACHES AN INFLECTION POINT, BEYOND WHICH THE MAIN INFLUENCE ON THE TRACK WILL BE THE INTENSITY OF THE SYSTEM AT THAT POINT IN THE FORECAST. IF THE SYSTEM CAN INTENSIFY MORE RAPIDLY IN THE NEXT 48 HOURS, THEN IT WILL FOLLOW A MORE SOUTHERLY TRACK, SOUTH OF 20N, MOVING WESTWARD UNDER THE DEEP-LAYER RIDGING. IF THE SYSTEM CANNOT INTENSIFY MUCH IN THE NEXT 48 HOURS, THEN IT WILL FOLLOW A MUCH MORE NORTHWESTWARD TRACK, MOVING ALONG THE LOW- TO MID-LEVEL FLOW WHICH IS ALIGNED MORE NORTHWEST-SOUTHEAST THAN THE DEEP-LAYER MEAN FLOW. THERE IS CONSIDERABLE UNCERTAINTY IN GLOBAL MODEL AND ENSEMBLE GUIDANCE, WHICH WILL BE DISCUSSED IN MORE DETAIL IN THE NEXT SECTION. THE SYSTEM IS EXPECTED TO INTENSIFY SLOWLY THROUGH THE NEXT 48 HOURS, UNDER GENERALLY FAVORABLE CONDITIONS. THE MAIN LIMITING FACTOR IN THE NEXT 48 HOURS WILL BE VORTEX MISALIGNMENT AND DRY MID-LEVEL AIR TO THE NORTH. BY TAU 48, THE SYSTEM IS EXPECTED TO ENCOUNTER STRONG NORTHEASTERLY FLOW ALOFT, WHICH WILL INCREASE THE SHEAR DRAMATICALLY. IF IT IS WELL-STRUCTURED AT THAT POINT, IT MAY BE ABLE TO FEND OFF THE WORST OF THE IMPACTS, BUT IF THE SYSTEM IS STILL ASYMMETRIC AND TILTED, THE SHEAR WILL IMPACT IT GREATLY AND THE SYSTEM WILL WEAKEN SIGNIFICANTLY. THE CURRENT FORECAST EXPECTS THE SYSTEM TO BE FAIRLY WELL-ALIGNED BY TAU 48, AND THUS BE ABLE TO FEND OFF THE SHEAR TO A DEGREE, RESULTING IN A FLATLINE INTENSITY TREND THROUGH TAU 72. ASSUMING A MORE SOUTHERLY TRAJECTORY, THE SYSTEM MOVES INTO A MORE FAVORABLE SHEAR ENVIRONMENT AFTER TAU 96, ALLOWING FOR MODEST REINTENSIFICATION THROUGH TAU 120. MODEL DISCUSSION: THE DETERMINISTIC GUIDANCE PACKAGE SHOWS A PRONOUNCED NORTHWARD SHIFT IN THE TRAJECTORY AFTER TAU 48. THE NAVGEM, GALWEM, ECMWF, GFS, GEFS AND THE CONSENSUS MEAN ARE TIGHTLY PACKED ON A NORTHWESTWARD TRACK AFTER TAU 72, TAKING THE SYSTEM JUST SOUTHWEST OF OKINAWA BY TAU 120. THE JGSM, ECENS MEAN, EC-AIFS AND SOME OTHER AI MODELS DEPICT A GENERALLY WESTWARD TRACK BELOW 20N THROUGH TAU 120, LEADING TO A CONSIDERABLE AMOUNT OF CROSS-TRACK UNCERTAINTY EXCEEDING 550NM. BOTH THE GEFS AND ECENS SHOW A SIMILAR POLEWARD SHIFT IN THE ENSEMBLE MEANS, AS WELL AS SHARPLY INCREASED UNCERTAINTY IN THE FORECAST TRAJECTORY. GEFS SHIFTED THE MOST AND EXHIBITS THE MOST UNCERTAINTY, WITH FIVE MEMBERS SHOWING A WESTWARD TRAJECTORY AND THE REMAINDER OF THE MEMBERS TURNING NORTHWEST TO VARYING DEGREES INCLUDING SEVERAL WHICH APPROACH SOUTHERN KYUSHU BY TAU 120. UNCERTAINTY HAS INCREASED WITH THE ECENS AS WELL, BUT TO A LESSER DEGREE, SHOWING APPROXIMATELY 10 MEMBERS SHOWING A WESTWARD TRACK BETWEEN 20N-22N, AND THE REMAINDER OF THE MEMBERS FOLLOWING A MORE NORTHWESTWARD TRACK AND ABOUT SEVEN TRACKING TOWARDS OR NORTH OF OKINAWA. THE JTWC FORECAST IS POSITIONED CLOSE TO THE ECENS MEAN AFTER TAU 72, WITH VERY LOW CONFIDENCE. INTENSITY GUIDANCE IS LIMITED AT THE MOMENT, WITH ONLY ONE (HAFS-A) MESOSCALE MODEL AVAILABLE. THE GUIDANCE OVERALL CONTINUES TO COME DOWN IN REFERENCE TO THE PEAK INTENSITY, AND THE JTWC FORECAST IS POSITIONED NEAR THE DECAY-SHIPS AND CONSENSUS MEAN THROUGH THE FORECAST PERIOD. HAFS-A IS ABOUT 5-10 KNOTS HIGHER THROUGH MOST OF THE FORECAST. OF NOTE, RICN, FRIA AND CTR1 RI AIDS ARE TRIPPED, BUT SEEM VERY UNLIKELY AT THIS TIME. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN