MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 40// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 12W (LIONROCK), LOCATED APPROXIMATELY 305 NM WEST OF IWO TO, HAS TRACKED NORTHEASTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS FRAGMENTED BANDING WRAPPING INTO A TIGHTLY WOUND WELL-DEFINED 16 NM EYE. SATELLITE IMAGERY ALSO SHOWS THE WEAKENED CONVECTION ON THE NORTHWESTERN PERIPHERY DUE TO SUBSIDENCE PROVIDED BY WEAK RIDGING POSITIONED BETWEEN 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 105 KNOTS AND IS BASED ON RECENT DVORAK ESTIMATES FROM RJTD AND PGTW REPORTING T5.5 (102 KNOTS) HEDGED SLIGHTLY HIGHER FROM KNES ESTIMATE OF T6.0 (115 KNOTS) AT 271500Z. A 271233 METOP-B ASCAT IMAGE SHOWS THE EXTENT OF GALE FORCE WINDS EXPANDING SIGNIFICANTLY TO THE SOUTH DUE TO AN INCREASING PRESSURE GRADIENT FROM THE BUILDING SOUTHERN RIDGE. 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 AND INTENSITY WILL MAINTAIN AROUND 105 KNOTS. GRADUAL OSCILLATIONS IN INTENSITY ARE EXPECTED AS SUBSIDENCE CONTINUES TO DISRUPT THE CONVECTION STRUCTURE ON THE NORTHWEST PERIPHERY. BEYOND TAU 24 STEADY WEAKENING IS EXPECTED AS THE ENVIRONMENT STARTS TO DETERIORATE. BEGINNING AROUND TAU 48 THE TRACK WILL SHIFT NORTHWEST AS STEERING TRANSITIONS FROM THE NER TO A 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 72. SOMEWHERE BETWEEN TAU 72 AND 96 TY 12W WILL START TRANSITIONING INTO AN EXTRATROPICAL SYSTEM BECOMING FULLY EXTRATROPICAL BY TAU 120. 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 INTO THE TROUGH. HWRF IS THE ONLY EXCEPTION SHOWING AN ABRUPT TURN EAST AROUND 40 DEGREES NORTH; ALSO AN UNLIKELY SCENARIO DUE TO THE NORTHERN RIDGE. 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. DUE TO THE DIFFERENCE IN MODEL SOLUTIONS AND VAST UNCERTAINTY THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN