South China Sea: Typhoon Nesat tracking west-southwestward as of Oct. 17 /update 3

Event

Typhoon Nesat (named Neneng in the Philippines) is tracking west-southwestward over the eastern South China Sea Oct. 17, having passed over the Babuyan Islands, Philippines, early Oct. 16. As of 14:00 CST the system's center of circulation was approximately 413 km (257 miles) southeast of Hong Kong.

Forecast models indicate that the system will weaken slightly as it continues to track west-southwestward across the South China Sea Oct. 17-18 and makes a close approach to the north of the Paracel Islands late Oct. 18-early Oct. 19. The system is forecast to weaken further and become a tropical storm as it turns to track westward and then west-northwestward Oct. 19-20, making a close approach to Hainan Island, China. Nesat is then likely to weaken into a tropical depression before making landfall over north-central Vietnam Oct. 21 and is expected to dissipate over central Laos Oct. 22. Some uncertainty remains in the track and intensity forecast, and changes could occur over the next few days.

As of Oct. 17, the China Meteorological Administration has issued a yellow typhoon warning (the second lowest level on a four-tier scale), advising that the storm will bring strong winds and rough seas to southern coastal waters and heavy rainfall along the central coast of Guangdong Province Oct. 17-18. The Honk Kong Observatory has issued Typhoon Warning No. 3 (level 3 of 10) due to the passing of the storm to the south. Nesat is also forecast to continue to bring heavy rainfall to parts of Taiwan through the remainder of Oct. 17. The Taiwan Central Weather Bureau has issued an extremely torrential rain advisory (the highest level on a four-tier scale) for mountainous areas of Taipei City and a torrential rain advisory for mountainous areas of Yilan County. Extremely heavy rain advisories have been issued for Keelung North Coast, New Taipei City, and the rest of Yilan County and heavy rain advisories have been issued for the rest of Taipei City, mountainous areas of Taoyuan City, mountainous areas of Hsinchu County, mountainous areas of Pingtung County, the Hengchun Peninsula, Hualien County, Taitung County, and Lanyu and Ludao Islands,

Officials could update and possibly extend the coverage of weather alerts over the coming days.

Disruptions are ongoing across parts of northern Luzon in the Philippines following the passing of the storm late Oct.15-16. Widespread flooding is ongoing and more than 27,000 people across parts of Cagayan Valley, Ilocos Region, and Cordillera Administrative Region have been affected by the storm. More than 700 people remain in evacuation shelters across the affected areas as of Oct. 17 and nearly 300 more are sheltering with friends or family. A state of calamity has been declared for the municipalities of Allacapan and Santa Ana in Cagayan province due to severe flooding. Dozens of roads across the region have been made impassable by floodwaters and damage assessments to reveal the full extent of damage caused by the storm are ongoing.

Hazardous Conditions
Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides are possible in hilly or mountainous areas, especially where heavy rainfall has saturated the soil.

Authorities could issue mandatory evacuation orders for flood-prone communities over the coming days. Disruptions to electricity and telecommunications services are possible where significant flooding or landslides impact utility networks.

Transport
Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Ponding on road surfaces could cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters. Flooding could block regional rail lines; freight and passenger train delays and cancellations are likely in areas that see heavy rainfall and track inundation.

Localized business disruptions may occur in low-lying areas; some businesses might not operate at full capacity because of flood damage to facilities, evacuations, and some employees' inability to reach work sites.

Advice

Monitor local media for weather updates and related advisories. Confirm all transport reservations and business appointments before travel. Make allowances for localized travel delays and potential supply chain disruptions where flooding has been forecast. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.

Resources

Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA)
China Meteorological Administration
Taiwan Central Weather Bureau
Hong Kong Observatory
Vietnam National Center for Hydro-Meteorological Forecasting (NCHMF)