MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (LAN) WARNING NR 20// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 25W (LAN), LOCATED APPROXIMATELY 427 NM SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS EXPANSIVE AND DEEP CONVECTIVE BANDS TIGHTLY WRAPPING INTO A LARGE (55 NM) RAGGED, ALBEIT SYMMETRICAL EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED THE EYE FEATURE. THE INITIAL INTENSITY OF 90 KNOTS IS BASED ON CONGRUENT AND CLOSELY-CLUSTERED DVORAK FIXES OF T5.0 FROM PGTW AND RJTD. UPPER LEVEL ANALYSIS INDICATES THAT THE SYSTEM IS IN AN AREA OF LOW (5-10 KNOT) VERTICAL WIND SHEAR (VWS) AND EXCELLENT DUAL CHANNEL OUTFLOW. ADDITIONALLY, ALONG-TRACK SEA SURFACE TEMPERATURES (SSTS) ARE VERY WARM (30 TO 31 CELSIUS). TY 25W IS TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO THE EAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 25W WILL BEGIN TO TRACK NORTH-NORTHEASTWARD OVER THE NEXT 48 HOURS UNDER THE INFLUENCE OF THE STR. AFTERWARD, THE SYSTEM WILL ACCELERATE AS IT RECURVES NORTHEASTWARD ON THE POLEWARD SIDE OF THE STR AXIS, CROSSING THE KANTO PLAIN OF HONSHU, JAPAN, BEFORE EXITING BACK INTO THE PACIFIC OCEAN BY TAU 72. FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST AND POLEWARD OUTFLOW WILL INCREASE AS THE SYSTEM APPROACHES THE MID-LATITUDE WESTERLIES. THIS INITIAL EXPOSURE TO THE WESTERLIES WILL ENHANCE OUTFLOW AND ALLOW FOR A PERIOD OF RAPID INTENSIFICATION, REACHING A PEAK OF 115 KNOTS AROUND TAU 24. AFTERWARD, THE SYSTEM WILL BEGIN TO GRADUALLY WEAKEN AS IT BEGINS TO INTERACT WITH A PASSING MID-LATITUDE TROUGH AND BECOMES EMBEDDED IN THE MID-LATITUDE WESTERLIES, STRONG VWS, COOLER SSTS, AND RUGGED TERRAIN OF HONSHU. BY TAU 48, TY 25W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AND BECOME A COLD CORE LOW WITH A VERY WIDE WIND FIELD BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. C. AFTER TAU 72, TY LAN WILL CONTINUE TO ACCELERATE NORTHEASTWARD DEEPER INTO THE BAROCLINIC ZONE. INCREASING VWS, COOLER SSTS, AND DRY AIR ENTRAINMENT WILL RAPIDLY ERODE THE COLD-CORE SYSTEM DOWN TO 45 KNOTS WITH STILL A RELATIVELY WIDE WIND FIELD. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT FOR THE TRACK DIRECTION, HOWEVER, VARIATIONS IN THE TRACK SPEED AFTER TAU 48 LEAD TO A SIGNIFICANT SPREAD IN THE GUIDANCE BY TAU 96. DUE TO THE UNCERTAINTY IN STORM SPEED IN THE LATER TAUS, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN