Indonesia: Further adverse weather forecast across much of the country through at least Oct. 24 /update 6

Event

Thunderstorms, heavy rains, strong winds, and possible flooding are forecast across much of Indonesia through at least Oct. 24. As of Oct. 21, the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG) has issued orange flood warnings (the middle level on a three-tier scale) for West and Central Java Oct. 21-23 and for East Java Oct. 21-22. Yellow heavy rainfall, strong winds, and thunderstorm warnings have been issued across much of the rest of Indonesia over the coming days. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Heavy rainfall in Trenggalek Regency in East Java Province Oct. 18 caused the Tawing River to overflow and the resultant flooding caused one fatality and affected thousands of people. Around 49 homes were also affected by landslides triggered by the heavy rainfall. Flash floods in Jembrana Regency, Bali, Oct. 16-17 killed two people and left one other missing. Thousands of people have also been affected by flooding in several other parts of the country in recent days, including Malang Regency in East Java Province, Luwu Regency in South Sulawesi Province, Central Majumu Regency in West Sulawesi Province, and Penukal Abab Lematang Ilir, Banyuasin, and Musi Banyuasin regencies in South Sumatra Province. Around 1,350 were also affected by a tornado in North Lombok Regency in West Nusa Tenggara Province Oct. 18.

Hazardous Conditions
Sustained heavy rainfall could trigger further flooding in low-lying communities near rivers, streams, and creeks. Coastal flooding is also possible during high tides. 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. Power outages could occur throughout the affected area.

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 also cause hazardous driving conditions on regional highways. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

The disruptive weather may cause delays and cancellations at airports across the affected area. Authorities may temporarily suspend port operations if strong winds trigger hazardous sea conditions, impacting freight and passenger maritime traffic. Flooding could block regional rail lines; freight and passenger train delays and cancellations are possible in areas with heavy rainfall and track blockages.

Disruptions triggered by inclement weather and resultant hazards, such as flooding, could persist well after conditions have improved - it could take days before any floodwaters recede and/or officials clear debris. If there is severe damage to infrastructure, repair or reconstruction efforts may result in residual disruptions.

Advice

Seek updated information on weather and related disruptions, including road conditions, before driving or routing shipments through areas where severe weather is forecast. Plan accordingly for potential freight delivery delays if routing shipments by truck through the affected area. Do not attempt to drive through flooded areas. Charge battery-powered devices if prolonged electricity outages occur.

Resources

Indonesian Agency for Meteorology, Climatology, and Geophysics
Indonesian Agency for Meteorology, Climatology, and Geophysics (Twitter)
Indonesian National Board for Disaster Management