South China Sea: Tropical Storm Kompasu tracking westward over South China Sea as of Oct. 12; landfall forecast in Hainan Province Oct. 13 /update 3

Event

Tropical Storm (TS) Kompasu (also known as Maring in the Philippines) is tracking westward over the South China Sea Oct. 12. As of 11:00 PHT, the storm's center of circulation was approximately 504 km (313 miles) north-northwest of Manila, Philippines, bringing strong winds to the Batanes and Babuyan Islands north of Luzon. Forecast models indicate the system will maintain its current intensity as it tracks westward; the storm will slightly weaken before making landfall in Hainan Province, China, late Oct. 13. Kompasu is then forecast to weaken further into a tropical storm as it continues westward into the Gulf of Tonkin Oct. 14. The system will likely make another landfall in Vietnam's Nghe An Province early Oct. 15 before dissipating over far northeastern Loei Province, Thailand, by early Oct. 17. The storm's track and intensity forecast remain somewhat uncertain, and the system may change accordingly over the coming days.

Emergency crews have reportedly evacuated at least 1,563 people from Cagayan Valley Region in the Philippines; at least one person died due to the storm. Reports also indicate power outages in 20 cities across Ilocos, Cagayan Valley, and Mimaropa regions. Authorities have restored power to at least 10 of the affected cities as of Oct. 12.

Government Advisories
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) has issued tropical cyclone wind signals (TCWS) in connection with TS Kompasu. TCWS 2, indicating damaging gale-to-storm-force winds are prevailing or forecast within 24 hours, is in effect for the provinces of Abra; Apayao; Batanes; Cagayan (including the Babuyan Islands); Ilocos Norte; Ilocos Sur; 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); Kalinga; and Mountain Province.

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 Aurora, Benguet, Bulacan, Ifugao, La Union, Nueva Ecija, Nueva Vizcaya, Pampanga, Pangasinan, Quirino, Tarlac, and Zambales.

Philippine authorities have also warned that Kompasu will bring significant rainfall to parts of the country through at least Oct. 13. Heavy-to-intense rain is forecast for the Ilocos Region and Abra, Benguet, Ifugao, and Mountain Province in the Cordillera Administrative Region. Moderate-to-heavy rain will probably affect the rest of the Cordillera Administrative Region and Bataan, Tarlac, and Zambales provinces; light-to-moderate rainfall is likely over the rest of Cagayan Valley and the rest of Central Luzon regions as well as Metro Manila. A red (second-highest level on a four-tier scale) flood advisory is in place for rivers and their tributaries in Cagayan and Isabela provinces in the Cagayan Valley Region, while orange flood advisories are in effect for rivers and their tributaries in Abra, Apayao, Benguet, Ifugao, Mountain Province, and Kalinga provinces in the Cordillera Administrative Regions as well as Ilocos Norte, Ilocos Sur, La Union, and Pangasinan provinces in Ilocos region.

Officials in Taiwan have issued related rain advisories from late Oct. 12 through early Oct. 13. Torrential Rain advisories (second-highest level on a four-tier scale) are in place for Hualien, western Taitung, and southern Yilan counties. Extremely Heavy Rain advisories (second-lowest level on a four-tier scale) have been issued for northeastern Pingtung, the rest of Taitung, and the rest of Yilan counties and southern New Taipei and eastern Taichung cities. Heavy Rain advisories (lowest level on a four-tier scale) are in effect for the rest of eastern Taiwan.

The China Meteorological Administration has issued a yellow typhoon warning due to the storm, forecasting that strong winds will affect coastal areas in Fujian, Guangdong, Guangxi, Hainan, and Zhejiang provinces until at least early Oct. 13. Heavy rainfall is forecast for northeastern Fujian, eastern and southern Guangdong, central and eastern Hainan Island, and central and eastern Zhejiang provinces over the same period, with the heaviest rainfall of 10-20 cm (4-8 inches) forecast over southeastern Guangdong and southeastern Zhejiang provinces.

Vietnamese officials have warned of heavy rain across Northern Vietnam Region and Quang Tri Province Oct. 13-14. Very heavy rain is forecast from Thanh Hoa to Quang Binh provinces 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)