MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (MALAKAS) WARNING NR 26// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 18W (MALAKAS), LOCATED APPROXIMATELY 231 NM WEST OF KADENA AB, HAS TRACKED NORTHEASTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS FURTHER WARMING OF CONVECTIVE CLOUD-TOPS, WHILE THE SYSTEM CONTINUES TO ELONGATE, INDICATING SLIGHT WEAKENING HAS OCCURRED. A 172205Z CORIOLIS 37 GHZ IMAGE REVEALS A DETERIORATION OF DEEP CONVECTION ALONG THE WESTERN SEMICIRCLE WHERE DRY, CONTINENTAL AIR IS IMPINGING ON THE SYSTEM. THE CURRENT BEST TRACK POSITION IS SUPPORTED BY THE AFOREMENTIONED IMAGERY WITH GOOD CONFIDENCE. THE INITIAL INTENSITY OF 80 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE DVORAK ESTIMATES AND REFLECTS THE WEAKENED STATE. UPPER- LEVEL ANALYSIS INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH GOOD OUTFLOW OFFSET BY MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR (VWS). SEA SURFACE TEMPERATURES REMAIN FAVORABLE (AROUND 28C), HOWEVER OCEAN HEAT CONTENT VALUES REMAINS UNFAVORABLE FOR DEVELOPMENT. THE CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 18W WILL CONTINUE TRACKING ON A NORTHEASTWARD TRAJECTORY AND ACCELERATING, AS IT ROUNDS THE WESTERN PERIPHERY OF THE STR, AND BECOMES EMBEDDED WITHIN THE STRONG MID-LATITUDE WESTERLIES. THIS SYSTEM IS FORECAST TO WEAKEN GRADUALLY THROUGH THE FIRST 48 HOURS AS VWS SLOWLY INCREASES. THE SYSTEM WILL MAKE LANDFALL OVER KYUSHU, JAPAN, BETWEEN TAU 36 AND 48. C. BEYOND TAU 72, TY MALAKAS WILL CONTINUE ACCELERATING NORTHEASTWARD ALONG COASTAL JAPAN WITHIN THE WESTERLIES. VWS WILL BECOME INCREASINGLY UNFAVORABLE, RESULTING IN RAPID WEAKENING OF THE SYSTEM. TC 18W IS FORECAST TO FULLY DISSIPATE BY TAU 96, JUST OFFSHORE OF TOKYO. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE FORECAST TRACK, HOWEVER THERE ARE SOME DIFFERENCES IN THE SPEED OF MOVEMENT OF TY MALAKAS. THEREFORE, THERE IS FAIR OVERALL CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN