MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (KOPPU) WARNING NR 17// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 24W (KOPPU), LOCATED APPROXIMATELY 202 NM EAST- NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM HAS DEVELOPED A 13-NM EYE AS DEEP CONVECTIVE BANDS WRAPPED TIGHTER INTO THE EYE. THE INITIAL POSITION IS BASED ON THE EYE FEATURE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 105 KNOTS IS BASED ON DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD AND REFLECTS THE INTENSIFIED STATE OF THE TYPHOON. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM REMAINS IN A HIGHLY FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR AND STRONG DUAL OUTFLOW. THE POLEWARD OUTFLOW SURGED OVER THE LAST SIX HOURS, AS EVIDENT ON ANIMATED WATER VAPOR IMAGERY. ADDITIONALLY, SEA SURFACE TEMPERATURES (SSTS) AT OVER 31 DEGREES CELSIUS IN THE PHILIPPINE SEA ARE HIGHLY CONDUCIVE FOR FURTHER DEVELOPMENT. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EXTENSION OF THE DEEP-LAYERED SUBTROPICAL 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 CONTINUE TO TRACK WESTWARD THROUGH TAU 24 ALONG THE SOUTHERN PERIPHERY OF THE STEERING STR EXTENSION. UPPER-LEVEL DYNAMICS AND SSTS WILL REMAIN FAVORABLE LEADING TO A PEAK INTENSITY OF 120 KNOTS AT TAU 12. THE CYCLONE WILL MAKE LANDFALL AROUND TAU 24 NEAR CASIGURAN THEN RAPIDLY DECAY AS IT DRAGS THROUGH THE RUGGED MOUNTAIN RANGES OF NORTHERN LUZON. AFTER TAU 24, TY 24W WILL TURN POLEWARD AS THE STR EXTENSION RETREATS AND AN INDUCED RIDGE FORMS BETWEEN TY 25W AND TY 24W AND ACTS AS THE WEAK PRIMARY STEERING MECHANISM FOR THE REMAINDER OF THE FORECAST. C. IN THE EXTENDED FORECAST, TY KOPPU WILL EXIT INTO THE LUZON STRAIT AT TROPICAL STORM STRENGTH AND CONTINUE TO TRACK NORTHWARD. MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH TAU 24, BUT SIGNIFICANTLY SPREADS AFTERWARDS. IN VIEW OF THIS, THE JTWC TRACK FORECAST CONFIDENCE LEVEL IS LOW.// NNNN NNNN