MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KOPPU) WARNING NR 22// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 24W (KOPPU), LOCATED APPROXIMATELY 100 NM NORTH- NORTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A DEEP CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC). AN 180632Z SSMI 85GHZ MICROWAVE IMAGE CONTINUES TO SHOW A MICROWAVE EYE FEATURE THAT SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE AND PROVIDES EVIDENCE THAT THE LLCC REMAINS OVER LAND. THE CURRENT INTENSITY HAS BEEN DECREASED TO 85 KNOTS BASED ON THE DETERIORATING STRUCTURE OF THE SYSTEM DUE TO LAND INTERACTION AS THE SYSTEM TRACKS THROUGH CENTRAL LUZON. UPPER LEVEL ANALYSIS INDICATES THAT THE SYSTEM REMAINS IN AN AREA OF LOW VERTICAL WIND SHEAR (VWS) AND EXCELLENT DUAL OUTFLOW CHANNELS. HOWEVER, FRICTIONAL EFFECTS CAUSED BY THE RUGGED TERRAIN ARE CAUSING THE RAPID WEAKENING OF THE SYSTEM. TY 24W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EXTENSION OF THE DEEP-LAYERED SUB-TROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 24W WILL TRACK ALONG THE SOUTHWESTERN PERIPHERY OF THE STR OVER THE NEXT 12 HOURS PRIOR TO TURNING POLEWARD. THE CYCLONE WILL TRACK POLEWARD AT A VERY SLOW PACE DUE TO A COMPETING STEERING MECHANISM FROM A SECONDARY STR TO THE WEST. TY KOPPU WILL CONTINUE TO WEAKEN DUE TO LAND INTERACTION AS IT MOVES ALONG THE WESTERN COAST OF LUZON. JUST BEFORE TAU 72, TY KOPPU WILL RE-EMERGE OVER WATER IN THE LUZON STRAIT AT TROPICAL STORM INTENSITY. C. IN THE EXTENDED TAUS, TY KOPPU WILL TRACK NORTHWARD AT A SLIGHTLY FASTER PACE AS AN EXTENSION OF THE STR BUILDS IN NORTHEAST OF THE SYSTEM. THE TYPHOON WILL BEGIN TO RE-INTENSIFY AS LOW VWS, GOOD OUTFLOW, AND WARM SSTS PREVAIL, REACHING 60 KNOTS BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE SHOWS A BIFURCATION DUE TO THE EXTENT OF THE STEERING STR WITH GFS, COAMPS-TC, AND HWRF TRACKING THE SYSTEM WESTWARD TOWARDS HONG KONG AND THE BULK OF THE GUIDANCE TRACKING THE SYSTEM NORTH TOWARDS TAIWAN. DUE TO THE CONTINUED SPREAD IN MODEL SOLUTIONS AND THE CHALLENGING STEERING ENVIRONMENT, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS.// NNNN NNNN