page_title: Typhoon Dujuan (2015)
section_title: Meteorological history
hierarchical_section_title: Typhoon Dujuan (2015) / Meteorological history
caption_attribution_description: English: Tropical Storm Dujuan with multiple vortices (including that fully-exposed low-level circulation center) on September 23, 2015.
context_page_description: Typhoon Dujuan, known in the Philippines as Typhoon Jenny, was the second most intense tropical cyclone of the Northwest Pacific Ocean in 2015 in terms of ten-minute maximum sustained winds, tied with Noul. The twenty-first named storm and the thirteenth typhoon of the 2015 Pacific typhoon season, Dujuan brought extremely powerful winds throughout the Yaeyama Islands and Taiwan in late September, causing 3 deaths in Taiwan. The typhoon also caused over ¥2.5 billion damage in East China.
  Dujuan originated as a monsoon depression, developing into a tropical storm on September 22. After slowly consolidating under an improving environment, the system intensified into a typhoon on September 25, and it started to present a large eye two days later. Dujuan reached its peak intensity on September 27 and made landfall over Taiwan on the next day. Interaction with the mountainous terrain of Taiwan significantly weakened the typhoon. Dujuan then made its second landfall over Fujian on September 29.
context_section_description: The origin of Typhoon Dujuan can be traced back to a tropical disturbance that formed over the Maloelap Atoll late on September 14. Convection remained very fragmented until September 20, when the Japan Meteorological Agency (JMA) upgraded the low-pressure area to a tropical depression east-northeast of Guam early on that day. Moreover, the Joint Typhoon Warning Center (JTWC) started to issue a Tropical Cyclone Formation Alert at the same time and indicated a monsoon depression, although the low-level circulation center (LLCC) was exposed and located east of the deep convective banding. In the afternoon on September 21, the JMA began to issue tropical cyclone warnings to the system, shortly before the JTWC also upgraded it to a tropical depression and designated it as 21W, based on the convective structure and a RapidSCAT image. On September 22, although the structure remained asymmetric with a fully exposed LLCC under easterly moderate vertical wind shear, the system still intensified into a tropical storm late on the same day and received the name Dujuan from the JMA.
  Many meteorological agencies initially forecasted a recurving track south of Japan to Dujuan, but those agencies changed it to a west-northwest track pointing to Taiwan after 24 hours. Dujuan developed smaller vortices rotating around a larger circulation centroid with deep convection along the western periphery on September 23; however, right after the storm entered the Philippine Area of Responsibility and was named Jenny by PAGASA, there was only one partially exposed LLCC within the consolidating structure in the afternoon, leading more model guidances to show a stairstep track vice a recurve scenario. When moving and organizing slowly on September 24, Dujuan was upgraded to a severe tropical storm early on that day, with an apparent eye revealed by a microwave imagery. Based on a ragged eye under decreasing vertical wind shear, both of the JTWC and then the JMA upgraded Dujuan to a typhoon early on September 25, as the system started to track northwestward along the southwestern periphery of a deep-layered subtropical ridge.
  Good divergent outflow as well as low vertical wind shear allowed Dujuan to intensify stably on September 26, yet dry air and subsidence were impacting the system at the same time, causing the western eyewall to break down. Due to decreasing dry air, Dujuan improved its overall structure significantly late on the same day when starting to track west-northwestward. Due to sea surface temperatures of 29 °C and improved radial outflow enhanced by a microscale anticyclone aloft, the JTWC indicated that the typhoon with an enlarged 80 km (50 miles) eye embedded in the highly deep and symmetric core had one-minute maximum sustained winds at 230 km/h (145 mph) early on September 27, equivalent to Category 4 of the Saffir–Simpson hurricane wind scale. This was increased to 240 km/h (150 mph) in post-season reanalysis, making Dujuan a super typhoon. Right after record-breaking winds were observed in Yonaguni of Okinawa, Japan around 16:00 JST (07:00 UTC) on September 28, the JMA raised Dujuan's estimated intensity of ten-minute maximum sustained winds to 205 km/h (125 mph) immediately, although the deep convective banding had begun to loosen with unraveling along the western side.
  Soon, the eye shrunk quickly and became cloud-filled when the eyewall was interacting with the terrain of Taiwan, indicating a weakening trend from both the JMA and the JTWC. The Central Weather Bureau (CWB) announced that Typhoon Dujuan had made landfall over Nan'ao, Yilan at 17:40 TST (09:40 UTC); at around 01:00 TST on September 29 (17:00 UTC on September 28), Dujuan emerged into the Taiwan Strait from Fangyuan, Changhua. Severely eroded by the Central Mountain Range and the Xueshan Range in Taiwan, the system rapidly weakened and was downgraded to a severe tropical storm by the JMA at 00:00 UTC on September 29. Dujuan made its second landfall over Xiuyu District, Putian of Fujian, China at around 08:50 CST (00:50 UTC) on September 29, shortly before the JTWC
caption: Tropical Storm Dujuan with a fully exposed LLCC on September 23
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