East China Sea: Typhoon Chanthu tracking northwards off the coast of Fujian Province, China, late Sept. 12 /update 8

Event

Typhoon Chanthu is tracking north-northeastward in the East China Sea, off the coast of Fujian Province, mainland China, as of late Sept. 12. As of 23:00 CST, the storm's center of circulation was approximately 165 km (102 miles) northeast of Taipei, Taiwan.

Chanthu is forecast to continue to weaken slightly as it changes direction and tracks north-northwestward early Sept. 13, and then make landfall as a typhoon over eastern portions of Daishan County, Zhejiang Province, mainland China, late Sept. 13-early Sept. 14. Chanthu will then continue weakening to a tropical storm as it tracks north-northwestwards before making a second landfall over Shanghai Sept. 14. Following landfall, the storm will weaken further and turn northeastward, moving out to sea through Sept. 15. Chanthu will then track parallel to the south coast of South Korea Sept. 17. The storm's track and intensity forecast remain uncertain, and the system may change accordingly over the coming days.

Government Advisories
As of late Sept. 12, the Central Weather Bureau in Taiwan has issued the following heavy rain advisories, which are in place through early Sept. 13:

• Yellow (lowest level on a four-tier scale): Keelung North Coast, Taipei City Mountain Area, New Taipei City Mountain Area, Taoyuan City Mountain Area, Hsinchu County Mountain Area

The China Meteorological Administration has issued a blue typhoon warning due to Chanthu, warning that heavy rain is forecast in northeastern Fujian, southeastern Jiangsu, and Shanghai, provinces as well as northern, eastern, and central Zhejiang Province through at least Sept. 13. Rainfall totals of 10-25 cm (4-10 inches) are possible in some areas.

As of early Sept. 13, 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): Okinawa Prefecture

As of early Sept. 13, the Korean Meteorological Administration has issued a windstorm advisory for the waters off the country's southwestern and western coasts, including off Jeju Island.

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 coastal areas of Taiwan, 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. 12, authorities canceled all domestic flights in Taiwan, while some international flights have also been canceled. At least 46 ferries to Matsu and other outlying islands were canceled. Reports indicate that train services in southeastern Taiwan will be partially disrupted through at least Sept. 13. At least 26,000 households remain without power.

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)