MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (SAOLA) WARNING NR 33// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 27W (SAOLA), LOCATED APPROXIMATELY 151 NM SOUTH OF KADENA, AB, OKINAWA, JAPAN, HAS TRACKED NORTHWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM HAS MOSTLY MAINTAINED DEEP CONVECTIVE BANDS FEEDING INTO A BROAD AND RAGGED LOW LEVEL CIRCULATION. ADDITIONALLY, THE EIR LOOP INDICATES NORTHERLY LOW LEVEL DRY AIR ENTRAINMENT ALONG THE WESTERN SEMI-CIRCLE. THE INITIAL POSITION IS BASED ON A WARM NOTCH FEATURE IN THE EIR LOOP THAT LINES UP WITH A WELL-DEFINED CIRCULATION FEATURE IN THE 271304Z ASCAT BULLSEYE PASS. THE ASCAT IMAGE WAS ALSO USED TO ADJUST THE TAU 00 34-KNOT WIND RADIUS. THE INITIAL INTENSITY OF 55 KNOTS IS BASED ON THE PGTW DVORAK ESTIMATE OF T3.5 AND REFLECTS THE SUSTAINED CONVECTIVE SIGNATURE OF TS 27W. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF LOW TO MODERATE (10-15 KNOT) VERTICAL WIND SHEAR (VWS) AND STRONG POLEWARD AND EQUATORWARD OUTFLOW. HOWEVER, THERE IS STRONG SUBSIDENCE ALONG THE WESTERN SEMI-CIRCLE CAUSED BY THE LEADING EDGE OF A MID-LATITUDE TROUGH DIGGING IN FROM CHINA. SSTS REMAIN RELATIVELY WARM NEAR 28 CELSIUS. THE CYCLONE IS TRACKING ALONG THE WESTERN BOUNDARY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS SAOLA WILL CONTINUE TRACKING NORTHWARD AS IT ROUNDS THE WESTERN EDGE OF THE STR OVER THE NEXT 24 HOURS, PASSING DIRECTLY OVER OKINAWA. AFTERWARD, IT WILL RECURVE AND ACCELERATE NORTHEASTWARD AS IT GETS EMBEDDED IN THE MID-LATITUDE WESTERLIES AND SKIRTS THE SOUTHERN COAST OF MAINLAND JAPAN. THE INITIAL EXPOSURE INTO THE STRONG WESTERLIES WILL ENHANCE POLEWARD OUTFLOW AND INTENSIFY 27W TO A PEAK OF 65 KNOTS BETWEEN TAU 12-24. AFTER TAU 24, THE STRONG WINDS WILL TRANSLATE TO STRONG VWS; ADDITIONALLY, COOL DRY AIR ADVECTION AND COOLING SSTS, CONCURRENT WITH EXTRA-TROPICAL TRANSITION (ETT) BY TAU 36, WILL STEADILY ERODE THE SYSTEM. BY TAU 48, THE SYSTEM WILL BECOME A STORM-FORCE COLD CORE LOW WITH A RAPIDLY EXPANDING WIND FIELD. BY TAU 72, SAOLA, WILL BE DEEPLY ABSORBED IN THE BAROCLINIC ZONE SOUTH OF KAMCHATKA. THE DYNAMIC MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT WITH THE FORECAST TRACK. HOWEVER, AS TYPICAL WITH RECURVE SCENARIOS, THERE IS SIGNIFICANT DIFFERENCES IN THE LATERAL SPEED AMONG THE TRACK MEMBERS. THE TRACK SPEEDS DIFFER EVEN GREATER AT THE ETT PHASE. IN VIEW OF THIS, THERE IS FAIR CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 36, THEN LOW CONFIDENCE AFTERWARD.// NNNN NNNN