Western Pacific: Tropical Storm Mirinae tracking northeastward in the western North Pacific Ocean away from the Izu Islands as of Aug. 8 /update 7

Event

Tropical Storm Mirinae is tracking northeastward in the western North Pacific Ocean away from the Izu Islands as of Aug. 8. As of 18:00 JST, the storm's center of circulation was approximately 219km (136 miles) east of Yokosuka, Kanagawa Prefecture. Forecast models indicate the system will continue northeastward, likely bringing tropical-storm-force winds to Kanto Region, potentially including the Greater Tokyo Area, through Aug. 8 before progressively turning further eastward as it weakens, dissipating in the North Pacific Ocean by Aug. 10. Some uncertainty remains in the system's track and intensity forecast, and changes may occur over the coming days.

Government Advisories
As of Aug. 8, the Japan Meteorological Agency has issued orange warnings (i.e., the second-highest level on a three-tier scale) for heavy rain, landslides, and flooding for parts of Chiba Prefecture. Additionally, yellow advisories (i.e., the lowest level on a three-tier scale) for heavy rain, landslides, inundation, flooding, storm gales, high waves, storm surge, and thunderstorms are in effect for the rest of the affected area.

Wave heights of up to 6 m (20 feet) are forecast for Kanto and Koshin regions through late Aug. 8, with lesser totals of up to 4 m (13 feet) possible in the Tohoku Region over the same period.

Authorities could 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. Localized evacuations are possible if weather conditions prove particularly hazardous.

Hazardous Conditions
The storm could bring heavy rainfall, strong winds, and rough seas to coastal parts of Japan 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
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, 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 could 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

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)
Japan Meteorological Agency