East China Sea: Tropical Storm Chanthu tracks northeastward in East China Sea early Sept. 17 /update 6

Event

Tropical Storm Chanthu has weakened slightly while tracking northeastward in the East China Sea early Sept. 17. As of 09:00 JST, the storm's center of circulation was approximately 206 km (125 miles) west of Sasebo, Japan. Chanthu is forecast to move in an east-northeasterly course, making multiple landfalls over western and southern Japan as a tropical storm Sept. 17-19. Chanthu is likely to make landfall in far northern Nagasaki, far northern Saga, then southern Yamaguchi prefectures, Sept. 17. The storm is then forecast to track east-northeastwards across the northern coast of Shikoku, making landfall over Ehime, Kagawa, Hyogo, and Osaka prefectures, early Sept. 18 while weakening gradually. Additional landfalls are forecast over southern Aichi Prefecture late Sept. 18 and southeastern Shizuoka Prefecture as well as Oshima Island, Tokyo Prefecture, early Sept. 19 before turning to track east-southeast across the Philippine Sea as it weakens into a tropical depression through early Sept. 20. The storm's track and intensity forecast remain uncertain, and the system may change accordingly over the coming days.

Reports indicate that authorities evacuated at least 196 people from landslide-prone areas across South Jeolla Province, 5,280 people from Nakatosa Town, and 4516 from Kuroshio Town and the entire Shimanto Town in Kochi Prefecture as of morning Sept. 17. Evacuations are also ongoing in parts of Nagasaki and Kumamoto prefectures.

Government Advisories
As of early Sept. 17, the Japan Meteorological Agency has issued the following warnings:

• Purple (second-highest level on a four-tier scale) landslide advisories due to heavy rain for western Kochi Prefecture.

• Red (the second-lowest level) warnings for severe weather are in place in parts of western Ehime, Fukuoka, Kagawa, western Kagoshima, central Kochi, Kumamoto, eastern Miyazaki, Nagasaki, southern Okayama, Saga, and Yamaguchi prefectures.

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

Heavy rain and strong winds are forecast over parts of Japan with rainfall of up to 30 cm (12 inches) over the Shikoku Region, 25 cm (10 inches) over the Tokai Region, 20 cm (8 inches) over the Kinki and Kanto regions, 18 cm (7 inches) over the Chugoku Region, 15 cm (6 inches) over the Kyushu, Tohoku, and Hokkaido regions, and 12 cm (4.5 inches) over the Hokuriku Region through the morning of Sept. 18.

The Korea Meteorological Administration has maintained a typhoon warning for the waters off the country's southeastern and southern coasts while a typhoon advisory is in effect for the southwestern coasts. Officials have also issued a heavy rain advisory for far southwestern North Gyeongsang and far southern North Chungcheong provinces.

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 parts of southern South Korea and nearly all of Japan outside of central and northern Hokkaido. 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. As of early Sept. 17, all ferries in Jeju Province and at least 89 passenger ships on 54 routes in South Jeolla Province remain suspended. Authorities canceled at least 23 flights at Jeju International Airport (CJU) while dozens of other flights were delayed. Officials at JR West in Japan have suspended trains on the Sanyo Shinkansen between Hiroshima and Hakata stations from the afternoon of Sept. 17 through at least late Sept. 17. Multiple regional trains and railways remain suspended due to the storm. Officials are likely to update information on train services as the conditions change. The ferries connecting Yawatahama, Ehime Prefecture with Oita, Matsuyama with Yanai in Yamaguchi Prefecture, and Hakata Port with Iki and Tsushima, have been canceled through at least Sept. 17. At least 18 flights from Osaka International Airport (ITM), two flights from Kansai International Airport (KIX), and all flights from Matsuyama Airport (MYJ) have been canceled. Japan Airlines and All Nippon Airways have canceled at least 73 and 77 flights, respectively, mainly from Kyushu.

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)