MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 41// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 12W (LIONROCK), LOCATED APPROXIMATELY 265 NM WEST- NORTHWEST OF IWO TO, HAS TRACKED NORTHEASTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS IMPROVED BANDING STRUCTURE IN THE LAST SIX HOURS WRAPPING INTO A TIGHTLY WOUND 15 NM EYE. SATELLITE IMAGERY ALSO SHOWS SLIGHTLY WEAKENED CONVECTION ON THE WESTERN PERIPHERY DUE TO SUBSIDENCE PROVIDED BY WEAK RIDGING BETWEEN TY 12W AND THE APPROACHING TROUGH MOVING OVER SOUTHERN JAPAN. THE INITIAL POSITION IS BASED ON SATELLITE EYE FIXES FROM PGTW AND RJTD WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 110 KNOTS AND IS BASED ON DVORAK ESTIMATES FROM RJTD REPORTING T5.5 (102 KNOTS) AND PGTW REPORTING T6.0 (115 KNOTS). UPPER-LEVEL ANALYSIS SHOWS STEADY RADIAL OUTFLOW WITH A VERY STRONG EQUATORWARD CHANNEL AND VERY LOW VERTICAL WIND SHEAR. SEA SURFACE TEMPERATURES REMAIN FAVORABLE AROUND 30 CELSIUS. CURRENTLY TY 12W IS TRACKING NORTHEAST ALONG THE PERIPHERY OF THE NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. IN THE NEAR-TERM FORECAST TY 12W WILL CONTINUE TRACKING NORTHEAST ALONG THE NER. ENVIRONMENTAL CONDITIONS WILL REMAIN FAVORABLE FOR THE NEXT 24 HOURS MAINTAINING THE INTENSITY AROUND 105 KNOTS WITH GRADUAL OSCILLATIONS. BEYOND TAU 24 STEADY WEAKENING IS EXPECTED AS THE ENVIRONMENT STARTS TO DETERIORATE. BEGINNING AROUND TAU 48 THE TRACK WILL BEGIN TO SHIFT NORTHWEST AS STEERING TRANSITIONS FROM THE NER TO A NORTHERN RIDGE POSITIONED SOUTH OF KAMCHATKA. C. IN THE EXTENDED FORECAST THE NORTHERN RIDGE WILL STEER TY 12W ALONG A NORTHWESTERN TRACK INTO A NEGATIVELY TILTED TROUGH OVER JAPAN. LANDFALL OVER NORTHERN HONSHU IS EXPECTED AROUND TAU 60. SOMEWHERE AROUND TAU 72 TY 12W WILL START TRANSITIONING INTO AN EXTRATROPICAL SYSTEM BECOMING FULLY EXTRATROPICAL BY TAU 96. DYNAMIC MODEL GUIDANCE IS SHOWING TWO DIFFERENT SCENARIOS. NAVGEM AND MESOSCALE SOLUTIONS, COAMPS-TC AND GFDN (BOTH INITIALIZED BY NAVGEM), ARE SHOWING A WEAKENED NER, RESULTING IN A TRACK MORE SOUTHWARD IN THE NEAR TERM AND A TRAJECTORY SUFFICIENTLY SOUTH TO AVOID THE STEERING TRANSITION; ULTIMATELY ENDING IN A QUASI- STATIONARY SCENARIO NEAR 150 DEGREES EAST. THIS IS AN UNLIKELY SOLUTION AS THE NER HAS ALREADY SHOWN SIGNIFICANT BUILDING, EVIDENCED BY THE EXPANDING SOUTHERN WIND FIELD. ALL OTHER SOLUTIONS IN THE MULTI-MODEL CONSENSUS ARE SHOWING TIGHT GROUPING THROUGH TAU 48 AND A TRANSITION TO THE NORTHWEST ENTERING THE TROUGH. HOWEVER DIFFERENCES ARE STILL EVIDENT IN THE POSITION AND TIMING OF THE WESTWARD TURN BEYOND TAU 48. THE FORECAST TRACK IS CLOSELY POSITIONED TO THE GFS AND ECMWF SOLUTIONS SHOWING A REALISTIC TURN TO THE NORTHWEST AND EVENTUAL CAPTURE BY THE TROUGH. THE JGSM AND HWRF SOLUTIONS SHIFTED RECENTLY SHOWING BETTER AGREEMENT WITH GFS AND ECMWF. NUMERICAL MODELS ARE STARTING TO COME INTO BETTER AGREEMENT BUT UNCERTAINTY IS STILL HIGH AS TY 12W MAKES THE TRANSITION TO THE NORTHWEST AND TRACKS INTO THE TROUGH LENDING LOW CONFIDENCE TO THE FORECAST TRACK.// NNNN NNNN