Typhoon Dujuan Floods Eastern Japan as 1.6 Million Flee

Typhoon Dujuan reached eastern Japan on Monday, forcing more than 1.67 million people into evacuation orders as record rainfall flooded roads, pushed rivers over their banks and triggered the country's highest emergency alert across five prefectures.

By Monday evening, authorities in a growing number of communities had activated Level 5 emergency safety alerts, the most severe tier of Japan's warning system, which is used when lives are in immediate danger and evacuation to a designated shelter may no longer be possible. According to Japan's Fire and Disaster Management Agency, more than three-quarters of a million households were under evacuation orders across Ibaraki, Chiba, Tokyo, Kanagawa and Shizuoka prefectures by Monday afternoon. People already trapped in affected areas were instructed to move to an upper floor, stay away from windows, slopes and rivers, and find the safest available position inside their current building.

Records fall on Izu Oshima and the mainland

The heaviest rain fell on Izu Oshima, a volcanic island about 110 kilometres south of Tokyo, where 686.5 millimetres fell in 24 hours by 5:20 pm local time, breaking the island's previous September record. Earlier that morning the island had recorded 387.5 millimetres; the total climbed by hundreds of millimetres within hours as Dujuan's strongest rainbands crossed the island.

The Japan Meteorological Agency issued a Level 5 special landslide warning for Oshima, indicating that a disaster may already have been occurring in vulnerable locations. The town of Oshima then issued its own Level 5 emergency safety alert across the entire municipality, covering roughly 1,900 households and about 3,000 residents.

Records also fell on the mainland. Funabashi in Chiba Prefecture received 331.5 millimetres of rain in 24 hours by early Monday evening, breaking its previous observational record of 285 millimetres set in October 2013. The Sakahata district of Kimitsu recorded more than 300 millimetres as repeated bands of intense rain crossed the prefecture. Sakura authorities issued a Level 5 alert after 80 millimetres of rain fell within a single hour. Sodegaura moved to the highest emergency level after reports of landslide impacts, with about 40,000 residents covered by the warning.

In Ichihara, rising water around the Yoro River system created a separate emergency. Authorities expanded Level 5 emergency safety instructions during the evening as flood-control operations continued at Takadaki Dam, where officials warned that emergency releases could become necessary if inflows kept overwhelming available storage.

Transport halted, flights grounded, UN trip delayed

Transport across eastern Japan suffered widespread disruption. Japan Airlines cancelled around 120 domestic flights and All Nippon Airways cancelled around 140, while international services at Tokyo's Haneda and Narita airports were also affected. East Japan Railway suspended or restricted operations on lines across parts of Chiba, Ibaraki and western Tokyo, and roads became impassable in some locations as drainage systems struggled with the volume of water.

At the Asian Games in central Japan's Aichi Prefecture, organisers postponed the equestrian eventing competition until Tuesday because of the approaching typhoon. Prime Minister Sanae Takaichi's departure for New York to attend the U.N. General Assembly was delayed by four hours, Reuters reported, with the government saying she would leave Tokyo at 11 pm JST.

The Japan Meteorological Agency warned that linear rain bands could form over the Kanto region and central Japan. These narrow bands, which have become a growing concern in Japan in recent years, can dump extraordinary amounts of rain over a small area for several hours and sharply raise the risk of flash floods.

Dujuan's strength on Monday night

At around 10:00 pm local time on Monday, Typhoon Dujuan was positioned roughly 140 kilometres east-southeast of Choshi in Chiba Prefecture. The typhoon carried a central pressure of around 960 hPa, maximum sustained winds of approximately 144 kilometres per hour and gusts around 198 kilometres per hour, and was moving northeast at about 35 kilometres per hour, with parts of Chiba and Ibaraki still inside its storm-force wind field.

Rainfall intensity began easing in some areas hit earlier in the day, but the danger did not end with the rain. Rivers can keep rising after the rain weakens, and slopes that have absorbed hundreds of millimetres of water can fail hours after the heaviest rain has passed. Attention remained focused on Chiba, the Izu Islands and areas farther north, where waterways were still carrying huge volumes of runoff well after Dujuan's strongest rainbands had moved through.

El Nino is driving the Pacific's dangerous season

Dujuan is the latest in a destructive run of Pacific storms driven by a strengthening El Nino, according to a Bloomberg report published Monday. The ocean pattern, which emerged in June and has been strengthening since, is creating conditions that favour tropical cyclones across much of the Pacific. Twelve tropical cyclones formed across the basin and the South China Sea in August, the most in a single month since 1961, according to the Hong Kong Observatory.

"Beyond the number of storms, what is striking is the scale of flooding, displacement, and economic disruption already seen in places including southern China, the Philippines, and the Mariana Islands," said Graeme Riddell, who leads climate and sustainability consulting for Asia-Pacific at Marsh.

The Atlantic has been quiet by comparison, with its calmest start since 1941. Pacific cyclones have caused more than 230 deaths since April, media reports show, while natural disasters including three back-to-back storms caused an estimated $8.5 billion in direct economic losses in China in July alone, according to government statistics.

The disruption has spread beyond the storms' paths. Container shipping giant Maersk issued an advisory this month saying a string of severe typhoons had caused congestion at some of the region's biggest ports, reducing on-time vessel arrivals at a time when supply chains are already strained by war, trade disputes and rising prices.

Jennifer Francis, a senior scientist at the Woodwell Climate Research Center, described the ocean heat wave off Mexico as "rocket fuel" for tropical disturbances, and said about 90 percent of the heat trapped by extra greenhouse gases, produced mainly by burning fossil fuels and destroying forests, goes into heating the ocean. El Nino helps by reducing the vertical wind shear that rips storms apart.

Forecasters expect the busy season to continue. Tropical Storm Polo was rapidly intensifying near southwestern Mexico on Monday, with the U.S. National Hurricane Center forecasting it to become a major hurricane with sustained winds near 260 kilometres per hour by Wednesday morning. James Cosgrove of Moody's said further activity is expected through the rest of September and October, and perhaps into November, as El Nino strengthens toward its forecast peak values.

Sources: Reuters, Above The Norm News, Bloomberg via BusinessWorld.