05 May 2023 | 10:25 AM UTC
Japan: Adverse weather forecast across much of the country through at least May 8
Heavy rainfall forecast across much of Japan through at least May 8. Possible flooding and transport, business, and utility disruptions.
Event
Heavy rainfall is forecast across much of Japan through at least May 8. A low-pressure system is forecast to develop in the Sea of Japan and will pass over northern Japan on May 6. A weather front extending from the system is expected to move south from northern to western Japan May 6-7, generating heavy rainfall across much of the country. Rainfall totals of 15 cm (6 inches) are expected in northern Kyushu Region and 8 cm (3 inches) in Hokuriku Region May 6. Heavy downpours could trigger flooding in low-lying areas and landslides on unstable slopes in affected areas across Japan. As of late May 5, the Japan Meteorological Agency has not issued any weather warnings above the lowest advisory level across Japan; however, authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.
Hazardous Conditions
Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible 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 possible in hilly or mountainous areas, especially where the soil has become saturated by heavy rainfall.
Authorities could issue mandatory evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are possible where significant flooding or landslides impact utility networks.
Transport
Floodwaters and debris flows may 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 that see heavy rainfall and potential track inundation.
Localized business disruptions may occur in low-lying areas; some businesses might not operate at full capacity because of flood damage to facilities, possible 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.
