msgid/genadmin/navpacmetoccen Pearl Harbor hi/jtwc// subj/prognostic reasoning for typhoon 09w warning nr12// rmks/ 1. For meteorologists. 2. 12 hour summary and analysis. A. Super typhoon 09w (Sepat) has intensified to super typhoon intensity over the past 12 hours. The system has tracked slightly south of west as the deep steering ridge to the north continues to build westward. B. The latest enhanced infrared images indicate a small 12-nm diameter cloud filled eye within a central convective shield that measures approximately 130 nm across. A 142255z SSMI 85ghz image also depicts this eye feature. Although poleward outflow has decreased, the system maintains very strong equatorial outflow and continues to intensify over 29c to 30c sea surface temperatures. Upper level ridging has continued to amplify ahead of the deep longwave trough over China, and TY 09w is now approaching a region of strong north- easterly (confluent) flow aloft. Current satellite-derived intensity estimates are clustered at 127 knots. 3. Forecast reasoning. A. The overall forecast philosophy has not changed since the last prognostic reasoning. B. TY 09w will transition to a poleward track within the next 24 hours as peripheral ridging combines with the deep layer (850 mb to 300 mb) subtropical ridging to the north. Once this occurs, the steering pattern will Orient southeast to northwest, promoting a northwestward track through 72 hours. The track forecast is consistent with the previous warning and closely follows the JGSM, NOGAPS, GFDN, and ECMWF solutions. Although poleward outflow will be restricted, the system is forecast to continue intensification, reaching maximum intensity near tau 36. C. The orientation of the steering flow is expected to remain southeast to northwest in the extended range. This trajectory takes TY 09w over southern Taiwan near tau 72 and into southeastern china near tau 96. TY 09w is expected to weaken as it approaches/interacts with Taiwan, encounters lower ocean heat content, and makes landfall in China. Forecast team: Charlie//