Philippine Sea: Tropical Depression 16W tracking westward near Guam Aug. 17 /update 4

Event

Tropical Depression 16W is tracking westward in the Philippine Sea Aug. 17. As of 13:00 ChST, the storm's center of circulation was approximately 56 km (35 miles) east-southeast of Navsta, Guam. Forecast models indicate that the system will make landfall over Guam as a tropical depression the afternoon of Aug. 17. Following its passage over Guam, 16W is forecast to strengthen rapidly into a typhoon in the Philippines Sea through Aug. 22 as it approaches Taiwan. Some uncertainty remains in the track and intensity forecast, and significant changes could occur in the coming days.

Government Advisories
As of 13:00 ChST Aug. 17, no warnings and watches are in effect. Officials could issue new warnings and/or watches in response to the developing system in the coming days.

Hazardous Conditions
The storm may bring heavy rainfall and rough seas to coastal areas of Guam 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. Torrential precipitation could trigger flash floods and mudslides.

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
In addition to the immediate threat to personal safety, 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. 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 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 adverse weather 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 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 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 (JTWC)
National Weather Service
Taiwan Central Weather Bureau