South China Sea: Severe Tropical Storm Kompasu tracking westward into South China Sea as of early Oct. 12; landfall forecast in Hainan Province Oct. 13 /update 2

Event

Severe Tropical Storm Kompasu (also known as Maring) is tracking westward into the South China Sea early Oct. 12. As of 20:00 PHT Oct. 11, the storm's center of circulation was approximately 482 km (299 miles) north of Manila, Philippines, bringing strong winds to the Philippines' Batanes and Babuyan Islands north of Luzon. Forecast models indicate the system will track westward over the coming days, largely maintaining its current strength before making landfall in Hainan Province, China, by late Oct. 13. Kompasu is then forecast to weaken to tropical-storm strength as it continues to track westward, transiting the Gulf of Tonkin Oct. 14; the storm will likely make another landfall in Vietnam's Ha Tinh Province by late Oct. 14 before dissipating near Vientiane, Laos, by late Oct. 16. The storm's track and intensity forecast remain somewhat uncertain, and the system may change accordingly over the coming days.

Government Advisories
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) has issued tropical cyclone wind signals (TCWS) in connection with Severe Tropical Storm Kompasu. TCWS 2, indicating damaging gale-to-storm-force winds are prevailing or forecast within 24 hours, is in effect for the provinces of Batanes; Cagayan (including the Babuyan Islands); the northern portion of Isabela (i.e., Palanan, Divilacan, Maconacon, Ilagan City, Tumauini, Cabagan, San Pablo, Santa Maria, Santo Tomas, Delfin Albano, Quirino, Gamu, Roxas, Mallig, and Quezon); Apayao; Kalinga; Mountain; Abra; Ilocos Norte; and Ilocos Sur.

TCWS 1, indicating strong winds are prevailing or forecast within 36 hours, is in effect for the rest of Isabela Province; the northern portion of Bataan Province (i.e., Samal, Morong, Dinalupihan, Abucay, Orani, and Hermosa); the northern portion of Quezon Province (i.e., General Nakar and Infanta) and the Polillo Islands; as well as the provinces of Nueva Vizcaya, Quirino, Ifugao, Benguet, La Union, Pangasinan, Aurora, Nueva Ecija, Tarlac, Zambales, Pampanga, and Bulacan.

Philippine authorities have also warned that Kompasu will bring significant rainfall to parts of the country through at least Oct. 12. Heavy-to-torrential rain is forecast for Batanes; the northern portion of Cagayan Province, including the Babuyan Islands; Cordillera Administrative Region; and Ilocos Region. Moderate-to-heavy rain is likely to affect the provinces of Zambales; Bataan; Tarlac; and the rest of Cagayan. Light-to-moderate rainfall is likely in Metro Manila; the rest of Cagayan Valley; and Central Luzon.

Officials in Taiwan have issued related rain advisories in effect from late Oct. 12 through early Oct. 13. Extremely Torrential Rain advisories (highest level on a four-tier scale) have been issued for Taichung City and Yilan County. Torrential Rain advisories (second-highest level on a four-tier scale) have been issued for New Taipei City and Hualien County. Extremely Heavy Rain advisories (second-lowest level on a four-tier scale) have been issued for Taipei City; Taoyuan City; Hsinchu County; Nantou County; Pingtung County; and Taitung County. Heavy Rain advisories (lowest level on a four-tier scale) have been issued for Keelung City and Kaohsiung City.

The China Meteorological Administration has issued a yellow typhoon warning in connection with the storm, forecasting that strong winds will affect coastal areas in the provinces of Hainan, Zhejiang, Fujian, and Guangdong until at least late Oct. 12; heavy rainfall is forecast for central and southern Zhejiang Province, northeastern Fujian Province, and and southeastern Guangdong Province over the same period.

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 remains possible if weather conditions prove particularly hazardous.

Hazardous Conditions
The storm may bring heavy rainfall, strong winds, and rough seas to coastal areas of the northern Philippines, far southern China, and central and northern Vietnam over the coming days. Sustained heavy rainfall in the northern Philippines, Taiwan, far southern China, most of Vietnam, Laos, northern Thailand, and northern Cambodia could trigger flooding in low-lying communities near streams, creeks, rivers, and urban areas with inadequate 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.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after weather 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 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
Cambodia Department of Meteorology
China Meteorological Administration
Philippine Atmospheric, Geophysical and Astronomical Services Administration
Taiwan Central Weather Bureau
Thai Meteorological Department
Vietnam National Centre for Hydro-Meteorological Forecasting (Vietnamese)