MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (IN-FA) WARNING NR 28// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 27W (IN-FA), LOCATED APPROXIMATELY 685 NM SOUTHWEST OF IWO TO, HAS TRACKED NORTH-NORTHEASTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY CONTINUES TO DEPICT A WELL-ORGANIZED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED BENEATH A LARGE, EXPANDING AREA OF DEEP CONVECTION. A 231756Z SSMI 85GHZ IMAGE SHOWS A MICROWAVE EYE FEATURE WITH THE BULK OF DEEP CONVECTION DISPLACED OVER THE NORTHERN SEMI-CIRCLE. HOWEVER, WITH THE EXCEPTION OF THE SOUTHWEST QUADRANT, THE SYSTEM HAS RETAINED ORGANIZED CORE CONVECTION. OVERALL, THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION BASED ON THE MICROWAVE IMAGERY. ANIMATED WATER VAPOR IMAGERY DEPICTS AN UPPER-LEVEL TROUGH POSITIONED OVER THE WESTERN PERIPHERY OF THE SYSTEM PRODUCING MODERATE SOUTHWESTERLY VERTICAL WIND SHEAR (VWS) AND DIFFLUENT FLOW. THE CURRENT INTENSITY IS MAINTAINED AT 90 KNOTS BASED ON THE CONVECTIVE STRUCTURE AND IS SUPPORTED BY DVORAK INTENSITY ESTIMATES OF T5.0 (90 KNOTS) FROM RJTD AND PGTW. TY 27W HAS ACCELERATED SLIGHTLY AS IT BEGINS TO ROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 27W WILL CONTINUE TO ROUND THE STR AXIS OVER THE NEXT 12 TO 24 HOURS. INCREASING INTERACTION WITH THE APPROACHING MID-LATITUDE TROUGH WILL LEAD TO A NORTHEASTWARD ACCELERATION INTO THE BAROCLINIC ZONE. ENVIRONMENTAL CONDITIONS WILL CONTINUE TO DETERIORATE AS VWS RAPIDLY INCREASES DUE TO THE STRONG WESTERLY WINDS FROM THE APPROACHING TROUGH. TY IN-FA WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 72. C. IN THE EXTENDED FORECAST, TY 27W WILL CONTINUE TO ACCELERATE NORTHEASTWARD ALONG THE NORTHWESTERN PERIPHERY OF THE STEERING STR. TY 27W WILL CONTINUE ETT AS IT EMBEDS DEEPER INTO THE MID-LATITUDE WESTERLY FLOW AND WILL COMPLETE ETT BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT, LEADING TO HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN