WDPN31 PGTW 190300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (CHOI-WAN)/ WARNING NR 29// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. CURRENTLY, THE SYSTEM IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) AND IS BEGINNING TO INTERACT WITH THE APPROACHING MID-LATITUDE TROUGH. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS TY 15W HAS AN ILL-DEFINED EYE WITH A LARGE (120 NM DIAMETER) SECONDARY OUTER EYEWALL WITH A RELATIVELY CLOUD FREE REGION ROTATING AROUND THE REMNANT INNER EYE. THE REMNANT INNER EYEWALL (40-50 NM) OF TY 15W HAS DIMINISHED SIGNIFICANTLY. DUE TO THE LACK OF INNER CORE SYMMETRY, TY 15W HAS LOST SOME INTENSITY DOWN TO 105 KNOTS. STILL, THIS SYSTEM IS A MATURE TROPICAL SYSTEM THAT HAS PASSED NORTH OF THE SUBTROPICAL RIDGE AND IS AHEAD OF A MID-LATITUDE TROUGH CURRENTLY OVER JAPAN. ANIMATED WATER VAPOR IMAGERY SHOWS THAT CONVECTION HAS SLIGHTLY ELONGATED IN A NORTHEAST TO SOUTHWEST ORIENTATION. THE TYPHOON CONTINUES TO EXHIBIT EXCELLENT, MAINLY POLEWARD OUTFLOW DUE TO THE APPROACHING MID-LATITUDE TROUGH. THE CURRENT INTENSITY OF 105 KNOTS IS BASED ON DVORAK SATELLITE INTENSITY FIXES FROM PGTW AND KNES. 3. FORECAST REASONING. A. THE FORECAST PHILOSOPHY HAS NOT CHANGED SINCE THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TYPHOON CHOI-WAN IS EXPECTED TO CONTINUE TRACKING ALONG THE NORTHWESTERN SIDE OF THE STR AND WEAKEN SLIGHTLY OVER THE NEXT 12 HOURS. AS THE SYSTEM APPROACHES THE STRONG WESTERLY WINDS ASSOCIATED WITH THE JET STREAM CROSSING JAPAN, THE CYCLONE WILL WEAKEN AT A FASTER PACE DUE TO INCREASING VERTICAL WIND SHEAR AND DECREASING SEA SURFACE TEMPERATURES. AFTER TAU 24, TY 15W WILL GRADUALLY TRANSITION INTO AN EXTRA-TROPICAL SYSTEM WITH COMPLETE TRANSITION BY TAU 48. DURING THIS PHASE, TY 15W WILL PROGRESSIVELY ACCELERATE TO THE NORTHEAST, STAYING WELL EAST OF MAINLAND JAPAN. THE OBJECTIVE AIDS GUIDANCE IS IN CLOSE AGREEMENT; THIS FORECAST TRACK FAVORS CONSENSUS, BUT ALONG TRACK SPEED IS FASTER THAN CONSENSUS TO CORRECT FOR KNOWN BIASES. FORECAST TEAM: BRAVO.// NNNN