Luzon Strait: Tropical Depression Choi-Wan tracking northeastward in the Luzon Strait, late June 4 /update 9

Event

Tropical Depression Choi-Wan (known in the Philippines as Dante) is tracking northeastward in the Luzon Strait, late June 4. As of 20:00 CST, the storm's center of circulation was approximately 346 km (215 miles) south of Taipei, Taiwan. Choi-Wan is forecast to maintain strength as a tropical depression through at least June 6. The system is tracking close to southern Taiwan and is forecast to bring impacts to the island through at least early June 5. Choi-Wan is forecast to continue tracking northeastward in the East China Sea near Japan's Ryukyu Islands, June 5. The system is forecast to weaken as it tracks into the northwestern Philippine Sea, June 6. Some uncertainty remains in the track and intensity forecast, and changes could occur over the coming days.

Government Advisories
As of 20:00 CST, Taiwan's Central Weather Bureau has issued the following warnings:

• Orange Extremely Heavy Rain: (third-highest level on a five-tier scale) Chiayi, Nantou, Yunlin, and Pintung Counties and Chiayi, Tainan, and Kaohsiung Cities

• Yellow Heavy Rain: Hsinchu, Miaoli, Changhua, and Yilan Counties and Keelung, Taipei, New Taipei, Taoyuan, and Taichung Cities

Authorities will likely issue new warnings or 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
Tropical Depression Choi-Wan is forecast to bring heavy rainfall, strong winds, and rough seas to coastal areas of Taiwan and southern Japan 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. Flooding could isolate some communities for several days. Rain-induced landslides are possible in steeply sloped terrains. Prolonged swells and storm surge generated by the system will likely result in coastal flooding as the system tracks close to land. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments.

In addition to the heavy rain, flooding, and storm surge, damaging wind gusts will persist. Widespread and prolonged power outages due to uprooted trees and toppled utility lines are possible.

Transport
In addition to the immediate threat to personal safety, inclement weather associated with the storm could trigger localized business, transport, and utility disruptions through at least June 6. Floodwaters and debris flows may render some bridges, rail networks, 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 airports.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after conditions improve. 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 low-income or underdeveloped areas of major urban centers due to 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 storm conditions. Heed all evacuation orders. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the high 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 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. Keep any necessary medications in a waterproof container.

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
Central Weather Bureau (Taiwan)