Japan: Tropical Depression Chanthu tracks eastward in Philippine Sea after landfall in Wakayama Prefecture early Sept. 18 /update 8

Event

Tropical Depression Chanthu has weakened while tracking eastward in Philippine Sea after landfall in Wakayama Prefecture early Sept. 18. As of 09:00 JST, the storm's center of circulation was approximately 313 km (194 miles) west-southwest of Yokosuka, Japan. Chanthu is forecast to continue tracking eastward, making a close approach to the northern Izu Islands, Tokyo Prefecture, late Sept. 18, passing between Kozu-shima and Shikine Island. It will likely continue tracking east, eventually dissipating over the North Pacific Ocean early Sept. 20. The storm's track and intensity forecast remain uncertain, and the system may change accordingly over the coming days.

Japanese officials have ordered evacuations in parts of Kanagawa, Miyazaki, and Shizuoka prefectures. Additional evacuations are possible. Authorities have reported at least five people injured in Fukuoka, Saga, and Nagasaki prefectures as Chanthu passed through the area. As of late Sept. 17, at least 2,240 households are without power across Fukuoka, Kumamoto, Miyazaki, Oita, and Saga prefectures.

Government Advisories
As of early Sept. 18, the Japan Meteorological Agency has issued the following warnings:

• Red (middle level on a three-tier scale) warnings for severe weather are in place in parts of far northwestern Chiba, Kanagawa, southern Saitama, northeastern Shizuoka, and Tokyo prefectures.

• Yellow advisories for potentially hazardous winds, landslides, heavy rain, and thunderstorms are in place for the rest of the affected area throughout central and southern Japan.

Heavy rain and strong winds are forecast over parts of Japan with rainfall of up to 25 cm (10 inches) over the Tokai Region, 18 cm (7 inches) over the Kanto and Koshin regions, and 8 cm (3 inches) over the Kinki Region through the morning of Sept. 19.

Authorities will likely issue new warnings or update existing advisories throughout the system's progression in the coming days. Weather warnings could remain active even after the system's immediate threat has diminished, as some areas may still be highly susceptible to rain-induced hazards. The possibility of localized evacuations cannot be discounted if weather conditions prove particularly hazardous.

Hazardous Conditions
The storm may bring heavy rainfall, strong winds, and rough seas over the coming days to most of central and southern Japan. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, rivers, and urban areas with easily overwhelmed or a lack of stormwater drainage systems.

Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall. Rain-induced landslides are possible in steeply sloped terrains. Flooding could isolate some communities for several days. Prolonged swells and storm surge generated by the system will likely result in coastal flooding. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments.

Transport
Inclement weather associated with the storm could trigger localized business, transport, and utility disruptions. Floodwaters and debris flows could render some bridges or roadways impassable, impacting overland travel in and around affected areas. Areal flooding in urban locations could also result in severe traffic congestion, while strong winds will pose a hazard to high-profile vehicles. Heavy rain and low visibility may trigger flight disruptions at regional airports.

Officials at JR West in Japan have suspended multiple passenger train services in western Japan while the Odakyu Electric Railway has suspended the Limited Express Romancecar connecting Shinjuku and Hakone. Officials will likely update information on train services as the conditions change. Ferry services connecting Kurihama, Kanagawa Prefecture, and Kanaya, Chiba Prefecture, have suspended operations as a precaution. At least 316 flights were canceled Sept. 17 but some have since resumed, while at least another 49 flights have been canceled Sept. 18. Additional flight, train, and passenger ferry cancelations or delays are likely in affected areas of southern and central Japan.

Disruptions triggered by inclement weather and resultant hazards, such as flooding could persist well after weather conditions have improved. If there is severe damage to infrastructure, repair or reconstruction efforts may exacerbate residual disruptions.

Health
Stagnant pools of water during and after flooding increase the incidence of insect- and waterborne diseases, such as dengue fever, cholera, and malaria. The threat of these disease outbreaks is usually elevated in the low-income or underdeveloped areas of major urban centers due to the presence of incomplete or open sewer lines. The latent threat of waterborne contaminants from inundated industrial sites cannot be discounted; exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.

Advice

Activate contingency plans in areas where officials forecast tropical storm conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the potential for severe flooding and storm surge. Stockpile water, batteries, and other essentials in advance. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents and necessary medications in waterproof containers. Observe strict food and water precautions, as municipalities could issue boil-water advisories following flooding events. Take precautions against insect- and waterborne diseases in the coming weeks.

Plan accordingly for protracted commercial, transport, and logistics disruptions in areas in the path of the storm, especially if vital infrastructure is damaged. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred. Confirm flights before checking out of hotels or driving to the airport; clearing passenger backlogs may take several days in some locations.

Resources

Joint Typhoon Warning Center
Japan Meteorological Agency (Japanese)
Korea Meteorological Administration (Korean)