North Pacific Ocean: Tropical Storm Rai tracking west-northwestward in the North Pacific Ocean early Dec. 14; close approach to Palau likely late Dec. 14 /update 1

Event

Tropical Storm Rai is tracking west-northwestward in the North Pacific Ocean early Dec. 14. As of 12:00 PWT, the storm's center of circulation was approximately 276 km (171 miles) east of Koror, Palau. Forecast models indicate the system will track westward in the North Pacific Ocean and make a close approach to northern Babeldaob Island, Palau, late Dec. 14. The system is forecast to further strengthen into a typhoon as it continues westward, making landfall over Dinagat Islands Province in the Philippines the afternoon of Dec. 16, with subsequent landfalls over the Visayas Dec. 17 and Palawan Province early Dec. 18. Some uncertainty remains in the track and intensity forecast, and changes could occur over the next few days.

Government Advisories
As of Dec. 14, the Palau National Weather Service has issued a typhoon warning for the Republic of Palau. Heavy rain of 10-20 cm (4-8 inches) and tropical storm to typhoon strength winds of 65-280 kph (39-150 mph) are likely through Dec. 14. A marine advisory small craft warning (red) flag is in place; boat travel is prohibited due to large waves of 3-4.5 meters (10-15 feet). Authorities have advised residents to either shelter-in-place or move to the closest evacuation shelter. All schools and nonessential government offices are closed. 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 cannot be discounted if weather conditions prove particularly hazardous.

Hazardous Conditions
Tropical Storm Rai is likely to bring heavy rainfall, strong winds, and rough seas to coastal areas of Palau over the coming days. 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 as the system approaches land. Persistent onshore flow could make it difficult for surge to recede and for water levels to decrease in coastal river catchments.

In addition to the heavy rain, flooding, and storm surge, the storm could produce damaging wind gusts. Tropical storm-force gusts in excess of 50 knots (90 kph, 60 mph) cannot be ruled out. 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 Dec. 19. 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.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after 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 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
Palau National Weather Service Facebook
Philippine Atmospheric Geophysical and Astronomical Services Administration