MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 21W (NEOGURI) WARNING NR 012// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 21W (NEOGURI), LOCATED APPROXIMATELY 295 NM SOUTH OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A COMPACT SYSTEM WITH A RAGGED, FORMATIVE 5NM EYE. A 190447Z AMSR2 89GHZ MICROWAVE IMAGE INDICATES A 30NM DIAMETER CORE WITH A SMALL MICROWAVE EYE FEATURE, WHICH SUPPORTS THE CURRENT POSITION WITH GOOD CONFIDENCE. THE CURRENT INTENSITY IS ASSESSED AT 65 KNOTS BASED ON A PGTW DVORAK INTENSITY ESTIMATE OF T4.0 (65 KNOTS), CONSISTENT WITH THE VISIBLE EYE STRUCTURE. UPPER-LEVEL ANALYSIS INDICATES LOW TO MODERATE (10-20 KNOTS) VERTICAL WIND SHEAR OFFSET BY ROBUST POLEWARD OUTFLOW INTO A DEEP UPPER-LEVEL TROUGH TO THE NORTH. SST VALUES OF 27-28C REMAIN CONDUCIVE FOR FURTHER DEVELOPMENT. THE SYSTEM IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 21W IS FORECAST TO TURN NORTHWARD TO NORTH-NORTHEASTWARD WITHIN THE NEXT 12-24 HOURS AS IT BEGINS TO RECURVE ALONG THE WESTERN PERIPHERY OF THE STR. BY TAU 36, THE SYSTEM WILL BEGIN TO INTERACT WITH A DEEP MIDLATITUDE SHORTWAVE TROUGH POSITIONED OVER THE EAST CHINA SEA AND RYUKYU ISLANDS, AND BEGIN EXTRA-TROPICAL TRANSITION (ETT). THE SYSTEM IS EXPECTED TO INTENSIFY SLIGHTLY TO A PEAK INTENSITY OF 75 KNOTS BY TAU 12, HOWEVER, VWS IS EXPECTED TO INCREASE SIGNIFICANTLY BY TAU 24 (35 KNOTS), WHICH WILL SERVE TO WEAKEN THE SYSTEM. AFTER TAU 24, TY 21W WILL ENCOUNTER INCREASING VWS (45-75 KNOTS) AS IT BECOMES EMBEDDED WITHIN THE MIDLATITUDE WESTERLIES AND SHOULD COMPLETE ETT BY TAU 72. DUE TO THE COMPLEX SYNOPTIC ENVIRONMENT, LARGE SPREAD IN MODEL SOLUTIONS AND EXTRA- TROPICAL NATURE OF THE SYSTEM, THERE IS HIGH UNCERTAINTY IN THE EXACT POSITION OF THE CENTER AS THE SYSTEM APPROACHES CENTRAL HONSHU. THE GLOBAL MODELS CONSISTENTLY FORECAST A STRONG JET TO REMAIN ENTRENCHED OVER JAPAN AND JUST TO THE SOUTH OF HONSHU, WHICH SHOULD SUPPORT A STRONG BAROCLINIC, COLD-CORE LOW AFTER TAU 60. HOWEVER, EXTREMELY STRONG VWS WILL SHRED THE DEEP CONVECTION OVER THE SYSTEM. C. BEYOND TAU 72, TY 21W IS EXPECTED TO ACCELERATE NORTHEASTWARD AS IT TRACKS UNDER A SOUTHWESTERLY JET. THIS EXTRA-TROPICAL SYSTEM IS EXPECTED TO MAINTAIN GALE-FORCE WINDS AS IT TRACKS EAST OF HONSHU. DUE TO THE LARGE SPREAD IN MODEL SOLUTIONS, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN