Typhoon Lan  Typhoon Lan, known in the Philippines as Typhoon Paolo, was the third-most intense tropical cyclone worldwide in 2017. A very large storm, Lan was the twenty-first tropical storm and ninth typhoon of the annual typhoon season. It originated from a tropical disturbance that the United States Naval Research Laboratory had begun tracking near Chuuk on October 11. Slowly consolidating, it developed into a tropical storm on October 15, and intensified into a typhoon on October 17. It expanded in size and turned northward on October 18, although the typhoon struggled to intensify for two days. On October 20, Lan grew into a very large typhoon and rapidly intensified, due to favorable conditions, with a large well-defined eye, reaching peak intensity as a "super typhoon" with 1-minute sustained winds of 250 km/h (155 mph) – a high-end Category 4-equivalent storm – late on the same day. Afterwards, encroaching dry air and shear caused the cyclone to begin weakening and turn extratropical, before it struck Japan on October 23 as a weaker typhoon. Later that day, it became fully extratropical before it was absorbed by a larger storm shortly afterwards. Lan caused significant impacts in Japan, with over 380,000 evacuations occurring in Japan, and the cancellations of several domestic flights. In total, approximately 17 deaths were attributed to the typhoon, mainly due to flooding from its rainbands. Damage totals were estimated to have been at least US$2 billion (2017 USD), making it one of the costliest typhoons to have struck Japan. The United States Naval Research Laboratory (NRL) initially mentioned a tropical disturbance over Chuuk on October 11. After the slow consolidation, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert to the elongated system early on October 14, shortly after the Japan Meteorological Agency (JMA) started to monitor it as a low-pressure area. The agency upgraded it to a tropical depression almost one day later and began to issue tropical cyclone warnings since 06:00 UTC on October 15. In the afternoon, the JTWC also upgraded it to a tropical depression assigning the designation "25W", which formative but shallow convective bands had become more organized, and symmetrically wrapped into a defined low-level circulation center. About three hours later, the JMA upgraded it to the twenty-first Northwest Pacific tropical storm in 2017 and assigned the international name "Lan", when it was located approximately 310 km (190 mi) to the northeast of Palau.