WDPN31 PGTW 241500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 23// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 15W (TEMBIN), LOCATED APPROXIMATELY 180 NM SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) SHOWS THE ORGANIZATION HAS BEEN ABLE TO CONSOLIDATE OVER THE PAST SIX HOURS, WITH CONVECTION BEGINNING TO WRAP INTO THE LOW LEVEL CIRCULATION CENTER (LLCC) AS THE LLCC HAS BEEN MOVING AWAY FROM TAIWAN. RADAR IMAGERY FROM TAIWAN HAS BEEN HELPFUL IN TRACKING OF TY 15W AND SUPPORTS THE DEVELOPMENT OF THE EYE OBSERVED IN EIR. THE CURRENT INTENSITY OF 75 KNOTS IS BASED ON DVORAK ESTIMATES FROM PGTW AND RJTD WHICH SUPPORT THE RECENT DEVELOPMENT NOTED PREVIOUS. UPPER LEVEL ANALYSIS INDICATES A WEAK POINT SOURCE ANTICYCLONE CONTINUES TO PROVIDE A RADIAL VENTING MECHANISM ALLOWING FOR THE RECENT INTENSIFICATION AND LOW VERTICAL WIND SHEAR ENVIRONMENT (05 TO 10 KNOTS). TY 15W IS TRACKING ALONG THE SOUTHERN EXTENSION OF A DEEP- LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AND APPEARS TO BE TRACKING INTO A WEAK STEERING ENVIRONMENT, BUT HAS NOT YET STARTED THE PREVIOUSLY FORECASTED COUNTER-CLOCKWISE LOOP UNDER THE SHIFTING STEERING INFLUENCES OF A NEAR EQUATORIAL RIDGE (NER), LOCATED TO THE SOUTHEAST OF TY 15W. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 15W WILL CONTINUE TO STEER IN A GENERAL WESTWARD DIRECTION WITHIN THE TAIWAN STRAIT FOR THE NEXT 24 HOURS, SLOWLY INTENSIFYING IN A FAVORABLE SURFACE ENVIRONMENT WITH THE POINT SOURCE ANTICYCLONE PROVIDING GOOD EQUATORWARD VENTING THROUGH TAU 48. AS THE STR CURRENTLY STEERING TY 15W BEGINS TO WEAKEN UNDER THE INFLUENCE OF TY 16W (BOLAVEN), THE NER TO THE SOUTHEAST IS EXPECTED TO BUILD BRINGING TY 15W EASTWARD. THE NER WILL MODIFY SLIGHTLY WITH THE PASSAGE OF TY 16W TO THE NORTHWEST, CAUSING TY 15W TO TURN TO THE EAST-NORTHEAST BETWEEN TAU 48 AND 72. C. AFTER TAU 72, TY 15W IS EXPECTED TO ACCELERATE NORTH- NORTHEASTWARD AS THE NER AMPLIFIES AND EVENTUALLY TRANSITIONS TO THE STR AS IT RE-BUILDS WHEN TY 16W MOVES INTO THE YELLOW SEA. THERE ARE SOME INDICATIONS THAT TY 16W WILL HAVE SOME BINARY INTERACTIONS WITH TY 15W IN THE LATER TAUS AS TY 16W PASSES TO THE NORTH OF TY 15W. AS TY 16W MOVES TO THE NORTHEAST OF TY 15W, THE OUTFLOW OF TY 16W IS EXPECTED TO HAMPER THE OUTFLOW FROM TY 15W, CAUSING THE SYSTEM TO SLOWLY WEAKEN AS IT TRACKS INTO THE YELLOW SEA BEYOND TAU 72. DYNAMIC MODEL GUIDANCE REMAINS IN FAIR AGREEMENT (ALL INDICATING A LOOPING TRACK WITH THE EXCEPTION OF GFDN) WITHIN 72 HOURS. HOWEVER, THERE IS A LARGE VARIATION IN THE FORECAST GUIDANCE BEYOND TAU 72 DUE TO THE POSSIBILITY OF INTERACTION WITH TY 16W AND THE VARIATION IN STR ORIENTATION. AS SUCH, THERE REMAINS LOW CONFIDENCE IN THE EXTENDED FORECAST TRACK.// NNNN