MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 017// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 93 NM WEST- NORTHWEST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTH- NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED A RAGGED PINHOLE EYE, NOW SHRUNK TO A 06-NM DIAMETER. SPIRAL BANDS ALSO REMAIN TIGHTLY WRAPPED INTO A COMPACT CENTRAL CONVECTION. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE, ADJUSTED FOR A SLIGHT WESTWARD TILT. THE INITIAL INTENSITY OF 115 KTS IS BASED THE DVORAK ESTIMATES OF T6.0/115KTS FROM RJTD AND PGTW. UPPER LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH A ROBUST RADIAL OUTFLOW AND LOW (10-15KT) VERTICAL WIND SHEAR (VWS). HOWEVER, HIGHER VWS VALUES ARE IMMINENTLY DOWNSTREAM. SEA SURFACE TEMPERATURES (SST) ARE STILL WARM AT 29-30C AND OCEAN HEAT CONTENT (OHC) VALUES ARE STILL HIGH. TY 10W IS TRACKING UNDER THE COMBINED STEERING INFLUENCE OF TWO SUBTROPICAL RIDGES (STR): ONE TO THE NNE AND ANOTHER TO THE ESE. 3. FORECAST REASONING. A. THIS FORECAST HIGHLIGHTS ANEW THE TRANSITION TO AN EXTRA- TROPICAL SYSTEM BY TAU 48, OTHERWISE, THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY MAYSAK WILL BEGIN TO TURN ON A MORE POLEWARD TRAJECTORY AS THE STR TO THE ESE RECEDES EQUATORWARD AND THE STR TO THE NNE ADJUSTS EASTWARD, BUILDS, AND BECOMES THE PRIMARY STEERING MECHANISM. INCREASING VWS, DECREASING OHC VALUES, AND COOLING SSTS WILL GRADUALLY WEAKEN THE SYSTEM TO 90 KTS BY TAU 36 JUST BEFORE LANDFALL INTO SOUTH KOREA. AFTER LANDFALL, LAND INTERACTION OVER THE RUGGED MOUNTAIN RANGES OF THE KOREAN PENINSULA, AND STRONG VWS WILL RAPIDLY ERODE TY 10W DOWN TO 60 KTS AS IT MOMENTARILY SPLASHES INTO THE SEA OF JAPAN AROUND TAU 48, THEN DOWN TO 30 KTS AFTER TAU 72 AFTER IT CROSSES INTO MANCHURIA. CONCURRENTLY AT TAU 36, THE SYSTEM WILL COMMENCE EXTRATROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE MIDLATITUDE TROUGH APPROACHING FROM THE NORTHWEST, COMPLETING ETT BY TAU 48, BECOMING AN INTENSE COLD CORE LOW. THERE IS A DISTINCT POSSIBILITY OF DISSIPATION OVER THE RUGGED TAEBAEK MOUNTAIN RANGES PRIOR TO TAU 72. THE NUMERICAL MODELS REMAIN IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK THAT IS LAID SLIGHTLY LEFT OF THE MULTI-MODEL CONSENSUS TO OFFSET AFUM, THE EXTREME RIGHT-OF-TRACK OUTLIER THAT IS UNREALISTICALLY DRIVING THE VORTEX INTO THE STR.// NNNN NNNN