20 Sep 2023 | 09:51 AM UTC
Japan: Adverse weather forecast across much of the country regions through at least Sept. 22 /update 1
Severe weather forecast across much of Japan through at least Sept. 22. Flooding, landslides, and associated disruptions likely.
Event
Severe weather is forecast across much of Japan through at least Sept. 22. As of Sept. 20, the Japan Meteorological Agency (JMA) has issued a severe weather bulletin warning of unstable weather conditions from western to northern Japan. Heavy rainfall and thunderstorms are expected in many areas during the night Sept. 21-22. Strong wind gusts, lightning, hail, and possible tornadoes may accompany storms. The JMA reported tornado-like gusts in Kaetsu, Niigata Prefecture, during the afternoon Sept. 20. Rainfall totals of around 12 cm (4.7 inches) in northern Kyuhsu, 10 cm (3.9 inches) in Chugoku, Hokuriku, Shikoku, and Tokai, and 8 cm (3.1 inches) in Kanto-Koshin, Kinki, and Tohoku regions are expected late Sept. 20-21. Heavy downpours could trigger flooding in low-lying areas and landslides on unstable slopes. Strong winds may cause property damage and power outages.
As of Sept. 20, the JMA has issued the following weather warnings across the affected area:
Red heavy rain/inundation warnings (the second lowest level on a four-tier scale): Parts of Chiba, Ibaraki, Saitama, and Tokyo prefectures in Kanto-Koshin Region, Kyoto Prefecture in Kinki Region,
Red flood warnings: Parts of Chiba and Tokyo prefectures in Kanto-Koshin Region.
Yellow heavy rain/inundation warning: Parts of Chiba and Tochigi prefectures in Kanto-Koshin Region, Kyoto Prefecture in Kinki Region, and Okayama Prefecture in Chugoku Region.
Yellow heavy rain/landslide warnings: Parts of Akita and Yamagata prefectures in Tohoku Region, Gunma Prefecture in Kanto-Koshin Region, and Niigata Prefecture in Hokuriku Region.
Yellow flood warnings: Parts of Chiba, Gunma, Saitama, and Tokyo prefectures in Kanto-Koshin Region, Niigata Prefecture in Hokuriku Region, and Okayama Prefecture in Chugoku Region.
Yellow storm/gale warnings: Abashiri, Mombetsu, and Nemuro regions in Hokkaido Prefecture, parts of Hyogo and Wakayama prefectures in Kinki Region, Ehime Prefecture in Shikoku Region, and across much of northern Kyushu Region.
Yellow high wave warnings: Abashiri, Nemuro, and Soya regions in Hokkaido Prefecture, parts of Hyogo Prefecture in Kinki Region, Ehime Prefecture in Shikoku Region, and Fukuoka, Nagasaki, and Saga prefectures in northern Kyushu Region.
Yellow storm surge warnings: Nemuro and Soya regions in Hokkaido Prefecture, parts of Aomori, Fukushima, and Iwate prefectures in Tohoku Region, Fukui, Ishikawa, and Toyama prefectures in Hokuriku Region, Hyogo and Kyoto prefectures in Kinki Region, Shimane Prefecture in Chugoku Region, and Nagasaki Prefecture in northern Kyushu Region.
Yellow thunderstorm warnings: Across Kanto-Koshin, Tokai, Hokuriku, Kinki, Shikoku, and northern Kyushu regions, much of Chugoku and southern Kyushu regions, and parts of Okinawa Prefecture.
Yellow dense fog warnings: Abashiri, Kamikawa, Kitami, Mombetsu, Rumoi, and Soya regions in Hokkaido Prefecture and across Gunma and Tochigi prefectures in Kanto-Koshin Region.
Officials will likely issue new alerts or update/rescind existing advisories as weather conditions develop over the coming days.
Sustained heavy rainfall will likely trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also probable in developed areas with easily overwhelmed stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are likely in hilly or mountainous areas, especially where heavy rainfall has saturated the soil.
Authorities could issue additional evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are likely where significant flooding or landslides impact utility networks.
Floodwaters and debris flows will likely render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.
Severe weather could also trigger flight delays and cancellations at airports in the affected areas. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas with heavy rainfall and potential track inundation.
Localized business disruptions will likely occur in low-lying areas; some businesses might not operate at full capacity because of flood damage to facilities, evacuations, and some employees' inability to reach work sites.
Advice
Monitor local media for weather updates and related advisories. Confirm all transport reservations and business appointments before travel. Make allowances for localized travel delays and potential supply chain disruptions where flooding has been forecast. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.
