South China Sea: Typhoon Rai tracking west-northwestwards across the South China Sea early Dec. 18 /update 9

Event

Typhoon Rai (known locally in the Philippines as Odette) is tracking west-northwestward across the South China Sea as of early Dec. 18 after transiting the central Philippines Dec. 16-17. Rai made its first landfall in Surigao del Norte Province and made multiple landfalls across the central Philippines Dec. 16-17. As of 05:00 PHT, the storm's center of circulation was approximately 590 km (367 miles) southwest of Manila, Philippines. Forecast models indicate the system will slightly strengthen over the coming hours as it continues in its current trajectory towards Vietnam. Rai will likely gradually turn northwestward as it weakens, making a close approach as a typhoon to Central Vietnam early Dec. 19 before turning to track north and making a close approach to the Paracel Islands early Dec. 20. The storm is subsequently projected to weaken rapidly into a tropical storm as it turns to track northeastwards, passing east of Hainan Province, China, Dec. 20-21 before turning to track east away from the province early Dec. 22. Some uncertainty remains in the track and intensity forecast, and changes could occur over the next few days.

Authorities in the Philippines evacuated at least 334,000 people across the Caraga, Central Visayas, Eastern Visayas, Northern Mindanao, Western Visayas, and Zamboanga Peninsula regions. Officials evacuated most of them ahead of the storm. Hundreds of schools and offices have been temporarily closed in the affected areas.

As of early Dec. 18, at least 12 fatalities have occurred across the central Philippines due to the storm's impact, about four of which occurred in Negros Occidental province, with the others reported in Surigao del Norte, Iloilo, Guimaras, and Bukidnon provinces. The casualty numbers will likely rise. Substantial infrastructure damage has occurred in Surigao City in northern Mindanao; reports indicate landslides, fallen trees, and power lines have cut off roads to the city. Flooding has also been reported in parts of Cagayan de Oro, Bohol, and Kabankalan, among other locations.

Authorities are working to restore power in many regions; however, as of early Dec. 18 outages are ongoing in Biliran, Bohol, Eastern Samar, Leyte, Northern Samar, Samar, Southern Leyte, and Surigao del Norte provinces, with partial outages in Agusan del Norte, Agusan del Sur, Antique, Cebu, Davao Oriental, Iloilo, Lanao del Norte, Misamis Occidental, Negros Oriental, and Surigao del Sur. Around 95 percent of Metro Cebu is without power; the Governor of Cebu Province has declared a state of calamity. Additional details on the situation will likely emerge in the coming days as authorities conduct thorough damage assessments.

Government Advisories
As of early Dec. 18, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) has rescinded most warnings but is maintaining a Tropical Cyclone Wind Signal (TCWS) 3 for the Kalayaan Islands in Palawan Province, a TCWS 2 for central Palawan, and a TCWS 1 for the rest of Palawan (including Calamian islands). Authorities have warned of heavy-to-torrential rainfall over the Kalayaan Islands through Dec. 18, while moderate-to-heavy rainfall is likely across Aurora, mainland Palawan, and northern Quezon (including Polillo Islands). There is still a moderate-to-high risk of storm surge in the areas under TCWS 3, which may cause flooding in low-lying coastal areas. Coastal flooding is possible in areas under TCWS 2 and TCWS 1 due to hazardous surf conditions.

Vietnamese officials have warned of heavy rain Thua Thien Hue to Khanh Hoa provinces from late Dec. 18-19. There is a high risk of flash floods, landslides in mountainous areas, and flooding in low-lying and riverside areas.

The China Meteorological Administration has issued a blue (lowest level on a four-tier scale) typhoon warning, warning of heavy rain over Nansha, Huangyan, and Zhongsha islands with the heaviest rain of 12-26 cm (4.5-10 inches) over northern Nansha Islands.

Authorities will probably 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. Officials may announce additional evacuations if weather conditions prove particularly hazardous.

Hazardous Conditions
Typhoon Rai will likely continue to bring heavy rainfall, strong winds, and rough seas to western parts of the Philippines in the coming hours. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, and rivers, as well as in urban areas with easily overwhelmed 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 sea swells and storm surge generated by the system could 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.

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

Transport
Inclement weather associated with the storm could trigger localized business, transport, and utility disruptions. 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 regional airports. Tugdan Airport (TBH) in Romblon Province was closed Dec. 15, and operations remain suspended at Mactan-Cebu International Airport (CEB) and Puerto Princesa International Airport (PPS) as of early Dec. 18. The terminal at Sayak Airport (IAO) in Siargao has sustained damages. The runway is cleared of debris, and planes carrying relief goods can land. Around 100 domestic flights were canceled Dec. 16 and dozens more Dec. 17-18. At least 73 seaports are also closed.

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.

Advice

Activate contingency plans in areas where officials forecast tropical storm or typhoon 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 and any 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
Philippine Atmospheric, Geophysical and Astronomical Services Administration
China Meteorological Administration
Vietnam National Center for Hydrometeorological Forecasting (Vietnamese)