MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (NAMTHEUN) WARNING NR 15// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 15W (NAMTHEUN), LOCATED APPROXIMATELY 96 NM SOUTH OF SASEBO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED IR AND VISIBLE SATELLITE IMAGERY SHOW THE SYSTEM HAS MAINTAINED CENTRAL CONVECTIVE SIGNATURE EVEN AS STRONG NORTHWARD VERTICAL WIND SHEAR (VWS) INUNDATE THE CYCLONE, PARTLY EXPOSING THE LOW LEVEL CIRCULATION THAT REMAINS TIGHTLY WOUND. THE INITIAL POSITION IS BASED ON A COMPOSITE RADAR LOOP FROM JMA AND PLACED WITHIN A TIGHT CLUSTER OF SATELLITE FIXES. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF HIGH (30-35 KNOT) VWS AND INCREASING LAND INTERACTION. HOWEVER, A STRONG POLEWARD OUTFLOW, AS EVIDENT ON ANIMATED WATER VAPOR IMAGERY IS SUSTAINING THE DISPLACED CENTRAL CONVECTION. THE CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY NAMTHEUN IS FORECAST TO CONTINUE TRACKING NORTHWARD ALONG THE WESTERN PERIPHERY OF THE STR AND WEAKEN AS IT GAINS LATITUDE DUE TO INCREASING VWS AND LAND INTERACTION. TY 15W WILL MAKE LANDFALL ALONG THE WESTERN COAST OF KYUSHU, JUST SOUTH OF SASEBO, NEAR TAU 12. AFTERWARDS THE SYSTEM WILL ROUND THE STR AXIS AND ACCELERATE NORTHEASTWARD WITH THE MID-LATITUDE WESTERLY FLOW. RAPID DECAY WILL BEGIN ONCE THE SYSTEM MOVES OVER COLD WATER (LESS THAN 25C) IN THE SEA OF JAPAN (SOJ). TY 15W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 24 AND COMPLETE ETT AS A WEAK COLD-CORE LOW BY TAU 48. THERE IS A DISTINCT POSSIBILITY THAT THE SYSTEM WILL DISSIPATE IN THE SOJ DURING ETT. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK; HOWEVER, ANY EASTWARD WOBBLE IN THE STORM MOTION WILL RESULT IN A MUCH WEAKER SYSTEM MAKING LANDFALL DUE TO INCREASED LAND INTERACTION WITH HIGHER TERRAIN.// NNNN NNNN