East China Sea: Typhoon Chanthu tracking north-northeastwards off the coast of Zhejiang Province, China, early Sept. 13 /update 9

Event

Typhoon Chanthu is tracking north-northeastward in the East China Sea, off the coast of Zhejiang Province, mainland China, as of early Sept. 13. As of 11:00 CST, the storm's center of circulation was approximately 504 km (313 miles) northwest of Kadena Air Base, Okinawa Prefecture, Japan.

Chanthu is forecast to weaken into a tropical storm as it tracks north alongside the eastern coasts of Zhejiang Province then Shanghai Municipality through Sept. 14. The storm is then forecast to turn sharply to track northeastward, towards South Korea. Chanthu is likely to continue weakening and make landfall as a tropical storm over Jeju Province, South Korea, on the afternoon of Sept. 16 and another landfall over far southern South Gyeongsang Province, South Korea, later that day. Following landfall, Chanthu is forecast to strengthen slightly while continuing to tracking northeast towards Ishikawa Prefecture, Japan, through early Sept. 18. The storm's track and intensity forecast remain uncertain, and the system may change accordingly over the coming days.

Government Advisories
As of early Sept. 13, the China Meteorological Administration has issued an orange typhoon warning due to Chanthu, warning that heavy rain is forecast in southeastern Jiangsu and northern Zhejiang provinces as well as Shanghai through at least Sept. 14. Rainfall totals of 25-28 cm (10-11 inches) are possible in some areas.

The Japan Meteorological Agency has issued the following advisories for thunderstorms, large waves, and storm surge, which are in place through Sept. 13:

• Yellow (lowest level on a four-tier scale): Kagoshima, Kumamoto, Nagasaki, and Okinawa prefectures

The Korean Meteorological Administration issued a windstorm advisory early Sept. 13 for the waters off the country's southwestern and western coasts, including off Jeju Island. A heavy rain advisory is in effect for southern and eastern Jeju Province as well as the mountainous areas of Jeju Province.

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 will likely bring heavy rainfall, strong winds, and rough seas to eastern mainland China, far southern Japan, and South Korea over the coming days. 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. 13, all flights at Shanghai Pudong International Airport (PVG) and Shanghai Hongqiao International Airport (SHA) are canceled from 11:00 CST Sept. 13 and 15:00 CST Sept. 13 respectively. Both airports are scheduled to be closed through at least Sept. 14. Some subway services in southern Shanghai are also suspended. All trains on the High-speed Rail on the Hangzhou-Ningbo, Beijing-Shanghai, Shanghai-Kunming, and Ningbo-Taiwan-Wenzhou routes have been canceled through at least Sept. 14. Authorities also suspended some port operations at the Shanghai and Zhejiang ports.

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 or typhoon 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
Taiwan Central Weather Bureau
China Meteorological Administration (Mandarin)
Japan Meteorological Agency (Japanese)
Korea Meteorological Administration (Korean)