Philippine Sea: Tropical Storm Omais tracking northwestward in the Philippine Sea as of early Aug. 22 /update 9

Event

Tropical Storm Omais is tracking northwestward in the Philippine Sea early Aug. 22. As of 06:00 JST, the storm's center of circulation was approximately 354 km (219 miles) south-southwest of Kadena Air Base, Okinawa Prefecture, Japan. Forecast models indicate that Omais will slightly strengthen as it continues northwest and makes a close approach to Miyako Island, Okinawa Prefecture, Japan, the afternoon of Aug. 22. The system is forecast to weaken slightly as it turns northeastward over the East China Sea toward South Korea, making landfall as a tropical storm over Jeju Province late Aug. 23. Omais will likely continue to track northeast and make another landfall over far southeastern South Jeolla Province early Aug. 24. After landfall, the storm will weaken as it tracks northeastward across South Gyeongsang and North Gyeongsang provinces and exit into the Sea of Japan the afternoon of Aug. 24. Omais is forecast to transition into a post-tropical cyclone with tropical storm strength winds as it tracks northeast over the Sea of Japan by early Aug. 25. Some uncertainty remains in the track and intensity forecast, and changes may occur in the coming days.

Government Advisories
As of early Aug. 22, the Japan Meteorological Agency has issued orange (the second-highest level on a three-tier scale) storm and large wave warnings for the Miyako Island Region, Okinawa Prefecture through at least Aug. 22. 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 far southern Japan and far eastern 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. Torrential precipitation could trigger flash floods and mudslides. Forecasts indicate that 10 cm (4 inches) of rainfall can be expected for the Okinawa Region through early Aug. 23.

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. Wave heights of up to 6 m (19.5 feet) can be expected for the Okinawa Region through Aug. 22.

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 major urban centers' low-income or underdeveloped areas 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

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. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred.

Resources

Joint Typhoon Warning Center (JTWC)
Japan Meteorological Agency (Japanese)
Korea Meteorological Administration (Korean)
China Meteorological Administration (Mandarin)