Philippine Sea: Typhoon Chanthu tracking northward southeast of Taiwan as of late Sept. 11 /update 6

Event

Typhoon Chanthu is tracking in a northerly direction in the Philippines Sea late Sept. 11. As of 23:00 CST Sept. 11, the storm's center of circulation was approximately 369 km (229 miles) south of Taipei. Forecast models indicate the system will continue to track northwards, making a close approach to eastern Taiwan through early Sept. 12. 11. The storm is forecast to weaken slightly as it passes east of Taiwan, before exiting into the far southern East China Sea late Sept. 12.

Chanthu is forecast to continue to lose strength as it tracks northward, making landfall east of Ningbo, Zhejiang Province, mainland China, late Sept. 13. It is forecast to continue tracking northwards through Sept. 14, before turning northeastward at the northern end of Hangzhou Bay late Sept. 14. Chanthu will then begin tacking east-northeastward through early Sept. 16 in the East China Sea, as it weakens to a tropical storm. The storm's track and intensity forecast remain uncertain, and the system may change accordingly over the coming days.

Government Advisories
Philippine officials forecast heavy-to-intense rainfall over the Babuyan Islands and Batanes, while moderate-to-heavy rain is forecast for Cagayan, Ilocos Norte, Ilocos Sur, Abra, Apayao, and Kalinga through early Sept. 12. Chanthu is likely to enhance the southwest monsoon, bringing monsoon rain over Metro Manila, the rest of Ilocos Region, the rest of Cordillera Administrative Region, and the western parts of Central Luzon and Southern Luzon through early Sept. 12.

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) has issued the following advisories associated with Chanthu:

• Tropical Cyclone Wind Signal (TCWS) 1*: Babuyan Islands

• Tropical Cyclone Wind Signal (TCWS) 2**: Batanes Province

*TCWS 1 means that strong winds are prevailing or expected within 36 hours.
**TCWS 2 means that damaging gale-force winds are prevailing or expected within 24 hours.

As of late Sept. 11, the Central Weather Bureau in Taiwan has issued the following advisories, which are in place through late Sept. 12:

• Yellow - Heavy Rain: Keeling North Coast, Taipei City, New Taipei City

• Orange - Extremely Heavy Rain: Henchung Peninsula, Yilan County, Hualien County, Lanyu and Ludao Islands

A Yellow advisory is the lowest level and an Orange advisory is the second-lowest level on a four-tier scale.

The China Meteorological Administration has warned that heavy rain is forecast in northeastern Fujian Province and eastern Zhejiang Province through at least late Sept. 12. Rainfall totals of over 20 cm (8 inches) are possible in some areas. 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
The storm will likely bring heavy rainfall, strong winds, and rough seas to coastal areas of the far northern Philippines, Taiwan, and eastern mainland China over 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. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments.

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.

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.

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 the presence of incomplete or open sewer lines. The latent threat of waterborne contaminants from inundated industrial sites cannot be discounted; exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.

Advice

Activate contingency plans in areas where officials forecast tropical storm or typhoon conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the 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 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
Taiwan Central Weather Bureau
China Meteorological Administration (Mandarin)
Japan Meteorological Agency (Japanese)