WDPN32 PGTW 260900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (SHANSHAN) WARNING NR 020// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 27.6N 132.8E INITIAL INTENSITY: 85 KTS GEOGRAPHIC REFERENCE: 275 NM EAST-NORTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 31 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTION INCREASING AROUND A RAGGED, APPROXIMATELY 10 NM DIAMETER EYE THAT BRIEFLY APPEARED AROUND THE 250000Z SYNOPTIC TIME AND HAS BEEN CONSISTENTLY EVIDENT IN A SERIES OF RECENT MICROWAVE SATELLITE IMAGES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A RECENT PGTW SATELLITE EYE FIX AND SUPPORTIVE 250415Z AMSR 37 GHZ IMAGERY. THE INITIAL INTENSITY OF 85 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A CONSENSUS OF RECENT MULTI-AGENCY SUBJECTIVE DVORAK AND AUTOMATED INTENSITY ESTIMATES. INCREASING DEEP CONVECTION AND THE PRESENCE OF AN EYE IN MULTIPLE SOURCES OF SATELLITE IMAGERY HIGHLIGHT ONGOING INTENSIFICATION UNDER THE INFLUENCE OF PASSAGE OVER VERY WARM WATER AND STRONG EQUATORWARD OUTFLOW, WHICH IS SUPPORTED BY A NARROW TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE SOUTH. HOWEVER, UPPER-LEVEL FEATURE TRACK WINDS AND ANIMATED WATER VAPOR IMAGERY ALSO INDICATE THAT PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR AWAITS THE SYSTEM JUST DOWNSTREAM. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS RJTD: T4.0 - 65 KTS RCTP: T4.0 - 65 KTS KNES: T4.5 - 77 KTS CIMSS SATCON: 84 KTS AT 260419Z CIMSS ADT: 82 KTS AT 260530Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 15-20 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK HAS SHIFTED A BIT TO THE WEST OF THE PREVIOUS FORECAST THROUGH TAU 72, WITH LANDFALL IN KYUSHU NOW EXPECTED TO OCCUR FARTHER TO THE NORTH. OTHERWISE, THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 11W WILL PROGRESS WESTWARD AND POLEWARD THROUGH TAU 48 AS IT APPROACHES THE STEERING RIDGE AXIS, THEN TURN EASTWARD TOWARD EVENTUAL LANDFALL IN KYUSHU BY TAU 72. DURING THE EXTENDED FORECAST PERIOD, THE SYSTEM IS EXPECTED TO SLOWLY ACCELERATE POLEWARD AND EASTWARD AHEAD OF A DEVELOPING MID-LATITUDE TROUGH. NEAR-TERM INTENSIFICATION IS EXPECTED AS THE SYSTEM PASSES OVER VERY WARM WATER AND EQUATORWARD OUTFLOW REMAINS FAVORABLE. HOWEVER, NORTHEASTERLY VERTICAL WIND SHEAR IS ON THE INCREASE AND EXPECTED TO LIMIT THE INTENSIFICATION RATE. EQUATORWARD OUTFLOW WILL ALSO BECOME MORE LIMITED AS A TUTT CELL TO THE SOUTH, CURRENTLY SUPPORTING THE SYSTEM, FILLS OVER THE NEXT DAY OR TWO. PASSAGE OVER LAND WILL RESULTING IN STEADY WEAKENING AFTER TAU 72. THE SYSTEM IS STILL EXPECTED TO BEGIN EXTRATROPICAL TRANSITION LATE IN THE FORECAST PERIOD AS IT BEGINS TO MERGE WITH THE AFOREMENTIONED MID-LATITUDE TROUGH AS A MUCH-WEAKENED TROPICAL STORM. MODEL DISCUSSION: THE LATEST MODEL GUIDANCE PACKAGE HAS ONCE AGAIN EXTENDED THE AXIS OF THE SUBTROPICAL STEERING RIDGE FARTHER TO THE WEST, NECESSITATING A COMMENSURATE ADJUSTMENT TO THE FORECAST TRACK. HOWEVER, BOTH DETERMINISTIC AND ENSEMBLE MODEL SOLUTIONS HAVE BEEN CONSISTENT IN THEIR GENERAL DEPICTION OF THE STEERING PATTERN FOR THE PAST THREE CYCLES. NAVGEM AND UKMET-BASED MODELS SUGGEST A WIDER TURN FARTHER THE WEST EARLY ON, BUT MOST CONSENSUS MODEL INDICATE LANDFALL TO THE SOUTH OF SASEBO BY TAU 96 AT THE LATEST. ALSO, THE UKMET AND GFS DETERMINISTIC SOLUTIONS DEPICT DISSIPATION AFTER LANDFALL RATHER THAN EXTRATROPICAL TRANSITION. BUT THE MAJORITY OF THE GUIDANCE, BOTH DETERMINISTIC MODELS AND ENSEMBLE MEMBERS, SUPPORT THE CURRENT FORECAST SCENARIO OF A STEADY TURN AROUND THE RIDGE AXIS FOLLOWED BY SLOW BUT STEADY ACCELERATION OVER LAND AND THE BEGINNING OF EXTRATROPICAL TRANSITION LATE IN THE FORECAST PERIOD. GIVEN THAT MODEL GUIDANCE IS BEGINNING TO SETTLE IN ON THE EXISTING FORECAST SCENARIO, BUT WITH SOME REMAINING DISAGREEMENTS, FORECAST CONFIDENCE IS MEDIUM ACROSS THE BOARD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN