South China Sea: Typhoon Rai tracking westwards across the South China Sea Dec. 18 /update 10

Event

Typhoon Rai (known locally in the Philippines as Odette) is tracking westward across the South China Sea as of 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 16:00 ICT, the storm's center of circulation was approximately 881 km (548 miles) southeast of Da Nang, Vietnam. Forecast models indicate the system will weaken slightly as it turns to track northwest towards Vietnam, making a close approach as a typhoon to Central Vietnam the afternoon of 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 passes west of the Paracel Islands early Dec. 20 and turns to track northeastward while weakening further into a tropical depression, passing southeast of Hainan Province, China, the afternoon of Dec. 20 to early Dec. 21. Rai is then forecast to turn to track east away from the province the afternoon of Dec. 21. No further landfalls are forecast. 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 364,000 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 Dec. 18, at least 21 fatalities have occurred across Surigao del Norte, Iloilo, Guimaras, Negros Occidental, and Bukidnon provinces due to the storm's impact. 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 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. Bohol and Cebu provinces have 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 Dec. 18, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) has rescinded most warnings but maintains a Tropical Cyclone Wind Signal (TCWS) 3 for the Kalayaan Islands in Palawan Province. Authorities have warned of heavy-to-torrential rainfall over the Kalayaan Islands through Dec. 18, while moderate-to-heavy rainfall is likely across the northern and eastern Cagayan Region and Apayao, Aurora, eastern Isabela, and northern Quezon (including Polillo Islands) provinces. 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.

Vietnamese officials have warned of heavy rain in Thua Thien Hue to Khanh Hoa provinces from late Dec. 18-19. Strong winds of 39-61 kph (25-38 mph) are forecasted across Quang Ngai, Binh Dinh, and Phu Yen provinces, while weaker winds of 29-49 kph (19-31 mph) are likely over Thua Thien Hue, Da Nang, Quang Nam, and Khanh Hoa provinces. The rivers in Quang Nam to Khanh Hoa provinces are in danger of flooding, especially the Song Ky Lo and Ba rivers in Phu Yen Province and the rivers in Quang Ngai, Binh Dinh, Khanh Hoa, and Quang Nam provinces. 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, rivers, and 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 the 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) through at least Dec. 19 and at Puerto Princesa International Airport (PPS). 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)