MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 39// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 698 NM SOUTH- SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A 26-NM EYE DESPITE A SLIGHT WEAKENING TREND WITH EYEWALL CONVECTION ERODING OVER THE NORTHWEST QUADRANT. A 271232Z METOP-B 89GHZ IMAGE SHOWS SLIGHT EROSION OF EYEWALL CONVECTION AS WELL AS WEAKENED, FRAGMENTED BANDING OVER THE NORTHERN SEMI-CIRCLE. ANIMATED WATER VAPOR IMAGERY INDICATES NEAR-RADIAL OUTFLOW ENHANCED BY AN UPPER LOW NEAR 33N 150E. THE CURRENT INTENSITY IS ASSESSED AT 105 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF 5.5 (102 KNOTS). TY 12W IS TRACKING EAST-NORTHEASTWARD ALONG THE NORTHERN PERIPHERY OF THE NEAR-EQUATORIAL RIDGE (NER). THE 500MB ANALYSIS INDICATES BROAD TROUGHING TO THE NORTH, WHICH HAS WEAKENED THE SUBTROPICAL RIDGE (STR), AND ALLOWED THE NER TO REMAIN THE DOMINANT STEERING INFLUENCE. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 12W WILL CONTINUE TO TRACK ALONG THE NORTHERN PERIPHERY OF THE NER THROUGH TAU 48. TY LIONROCK IS FORECAST TO MAINTAIN INTENSITY NEAR 105 KNOTS THROUGH THIS PERIOD DUE TO FAVORABLE ENVIRONMENTAL CONDITIONS. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PHASE OF THE JTWC FORECAST TRACK. AFTER TAU 48, THE DYNAMIC MODEL TRACKERS DIVERGE WITH MAJOR DIFFERENCES IN TRACK DESPITE CONSISTENT DEPICTION OF THE MAJOR SYNOPTIC FEATURES (MAJOR SHORTWAVE TROUGH AND THE POSITION OF THE STRONG RIDGE NORTHEAST OF JAPAN). C. AFTER TAU 72, TY 12W IS FORECAST TO RE-CURVE OVER NORTHERN JAPAN AND TO WEAKEN AS IT ENCOUNTERS INCREASING VERTICAL WIND SHEAR (VWS) AND COOLER SST. FURTHER WEAKENING IS EXPECTED AS THE SYSTEM CROSSES NORTHERN HONSHU AND ENCOUNTERS STRONGER VWS. THE DYNAMIC MODEL TRACKERS ARE IN POOR AGREEMENT WITH TWO DISTINCT CLUSTERS OF TRACKERS. THE FIRST CLUSTER DEPICTS A RAPID RE-CURVE TRACK OVER CENTRAL TO NORTHERN JAPAN AND THEN INTO NORTHEAST ASIA, AND INCLUDES THE JENS, JGSM, ECMWF, NAVGEM AND UKMET TRACKERS. JENS AND JGSM CONTINUE TO DEPICT AN UNLIKELY TRACK DIRECTLY INTO THE SHORTWAVE TROUGH WHILE ECMWF, NAVGEM AND UKMET HAVE SHIFTED NORTH TO A MORE REALISTIC RE-CURVE POINT BUT STILL SHOW A CYCLONIC TRACK INTO THE OCCLUDED LOW. THE SECOND CLUSTER OF TRACKERS INDICATES A NORTHEAST TO EAST-NORTHEAST TRACK AND QUASI-STATIONARY TRACK MOTION WELL TO THE SOUTHEAST OF NORTHERN JAPAN AND INCLUDES GFDN, GFS, COMAPS-TC AND HWRF. AEMN INDICATES A QUASI-STATIONARY TRACK JUST EAST OF TOKYO. THESE MODELS APPEAR TO STALL THE SYSTEM AS IT ENTERS A WEAK STEERING ENVIRONMENT BETWEEN THE MAJOR TROUGH OVER JAPAN AND ANOTHER DEEP TROUGH TO THE NORTHEAST. THE JTWC TRACK PHILOSOPHY FAVORS THE FIRST CLUSTER OF MODEL TRACKERS, WHICH PRESENT A REALISTIC SCENARIO, BUT WITH SLOWER TRACK SPEEDS. ERRATIC PERFORMANCE OF SEVERAL MODELS IS ALSO CREATING MUCH UNCERTAINTY IN THE TRACK FORECAST. DUE TO THE HIGH DEGREE OF UNCERTAINTY, BEYOND TAU 48, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN