Philippine Sea: Tropical Storm Nesat tracks westward in Philippine Sea late Oct. 15 /update 1

Event

Tropical Storm Nesat (named Neneng in the Philippines) was tracking westward over the Philippine Sea late Oct. 15. As of 20:00 PHST, the system's center of circulation was approximately 513 km (319 miles) north-northeast of Manila, Philippines.

Forecast models indicate that the system will pass over the Philippines' Babuyan Islands into early Oct. 16, with landfalls likely over Camiguin Island and Dalupiri Island. The system is then likely to strengthen into a typhoon as it tracks west-northwestward into the South China Sea Oct. 16-early Oct. 17. Nesat is subsequently forecast to continue to strengthen as it takes a turn to track southwestward Oct. 17-18. The storm is likely to weaken slightly as it turns to track west-southwestward late Oct. 18 and makes a close approach to the Paracel Islands Oct. 19. The system is then forecast to weaken further as it turns to track northwestward and makes a close approach to Hainan Island, China, Oct. 20. Some uncertainty remains in the track and intensity forecast, and changes could occur over the next few days.

As of early Oct. 16, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) had issued a Tropical Cyclone Wind Signal (TCWS) No. 2 alert (second-lowest level on a five-tier scale) for Batanes, Cagayan (including the Babuyan Islands), Apayao, northern Abra, and Ilocos Norte provinces. A TCWS No. 1 alert has been issued for parts of northern and central Isabela, Kalinga, the rest of Abra, Mountain Province, northern Ifugao, and northern and central Ilocos Sur provinces.

PAGASA has warned of heavy-to-intense rainfall in Batanes, Apayao, Ilocos Norte, and Cagayan, including the Babuyan Islands, as well as moderate-to-heavy rainfall over Abra, Kalinga, Mountain Province, and the northern parts of Ilocos Sur and Isabela over the coming hours. Light-to-moderate with at times heavy rainfall is also forecast over the rest of Isabela, Ilocos Sur, and the Cordillera Administrative Region over the coming hours. Moderate-to-heavy rainfall, with intense rainfall at times, is forecast over Ilocos Norte, northern Ilocos Sur, and Abra through the rest of Oct. 16. Light-to-moderate rainfall, at times including heavy rainfall, is also forecast for Batanes, the Babuyan Islands, Apayao, Kalinga, Mountain Province, and the rest of Ilocos Sur through the rest of Oct. 16. The heavy downpours could trigger flooding and landslides in parts of the affected areas.

The China Meteorological Administration has issued a blue typhoon warning (the lowest level on a four-tier scale), advising that the storm will bring rough seas to southern coastal waters. Nesat is also forecast to bring heavy rainfall to parts of Taiwan. 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, the rest of Taipei City, New Taipei City, mountainous areas of Hsinchu County, and mountainous areas of Taichung City, as well as heavy rain advisories for Taoyuan City, the rest of Hsinchu County, the rest of Yilan County, and Hualien County,

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

Authorities in Cagayan Province had preemptively evacuated residents in parts of Baggao Municipality ahead of the storm's approach. More than 1,000 people across parts of northern Luzon are still being accommodated in evacuation centers following the passing of Tropical Depression Maymay, which moved over the region Oct. 12-13.

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