Philippine Sea: Typhoon Surigae tracking north-northwestward near the Philippines late April 20 /update 11

Event

Typhoon Surigae (known in the Philippines as Bising) is tracking north-northwestward in the Philippine Sea, as of late April 20. As of 20:00 PHST, the storm's center of circulation was approximately 565 km (351 miles) east of Manila. Forecast models indicate the storm will continue to slowly weaken as it tracks northward off the eastern Philippines coastline through April 22 and then turn eastward through at least April 25 as it begins to transition into an Extratropical Cyclone. Projections do not indicate landfall; the storm will maintain a parallel course off the eastern Philippines through at least April 22. Some uncertainty remains in the track and intensity forecast, and changes could occur in the coming days. At least two people in the Visayas, central Philippines, have died due to the system as of April 20.

Government Advisories
The Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) continues to maintain Tropical Cyclone Wind Signal warnings as of the evening of April 20. The Tropical Cyclone Wind Signal No. 2 is in effect for eastern portions of Cagayan, the eastern portion of Isabela, the northern portion of Aurora, and Catanduanes. Additionally, the Tropical Cyclone Wind Signal No. 1 is in place for Batanes, the rest of Cagayan including Babuyan Islands, the rest of Isabela, Quirino, Apayao, Kalinga, the eastern portion of Mountain Province, the eastern portion of Ifugao, the northeastern portion of Nueva Vizcaya, the central portion of Aurora, the eastern portion of Quezon including Polillo Islands, Camarines Norte, and Camarines Sur. 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.

Surigae has reportedly led to more than 100,000 people evacuating in the Philippines as of April 20. Local authorities in some localities, including Catanduanes Province's Virac Municipality and central and eastern parts of Northern Samar Provinces, have ordered thousands of locals to evacuate. Further localized evacuations may occur 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 in the coming days. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, rivers, and urban areas with easily overwhelmed or a lack of 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 as the system approaches land. 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 heavy rainfall, flooding, and storm surge, Surigae will produce damaging wind gusts as it continues to track towards the eastern Philippines. Power disruptions have affected parts of the Philippines, including Cebu, Eastern Samar, Leyte, and Southern Leyte provinces, as of April 20. Additional 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 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, including Catanduanes Province's Virac Airport (VRC). The system has also led to landslides that block roads in parts of Catanduanes Province. Local officials in the Philippines have reportedly suspended land and sea travel in some eastern areas.

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.

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 the low-income or underdeveloped areas of major urban centers due to incomplete or open sewer lines. The latent threat of waterborne contaminants from inundated industrial sites cannot be discounted; exposure to raw sewerage 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 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
Philippine Atmospheric Geophysical and Astronomical Services Administration
Japan Meteorological Agency