Indonesia: Adverse weather forecast nationwide through at least June 23 /update 1

Event

Thunderstorms, heavy rains, strong winds, and flooding are forecast across much of Indonesia through at least June 23. As of June 17, the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG) has issued orange (middle level on a three-tier scale) flood warnings across South and Southeast Sulawesi provinces. Yellow thunderstorm, strong wind, flood, and heavy rain warnings are in place across much of Indonesia through June 19. The BMKG has also warned that coastal flooding is possible in many coastal areas of the country through at least June 23 due to dangerous tides associated with the ongoing Super Full Moon phenomenon. Authorities will likely issue new alerts or update/rescind existing advisories as weather conditions change over the coming days.

Severe weather events have caused disruptions across many parts of Indonesia in recent days. Coastal abrasion in South Minahasa Regency in North Sulawesi Province has led to the evacuation of 266 residents as of June 16. At least 15 houses have collapsed and damage has been caused to bridges, roads, and other homes and infrastructure in the area. A tornado caused damage to 86 homes, affecting around 430 people, in Lahat Regency in South Sulawesi Province June 16. Flooding caused by the overflowing Moko River in Poso Regency, Central Sulawesi Province, June 15 has affected around 750 people. Heavy rainfall also triggered flooding in South Tapanuli Regency in North Sumatra Province June 15, affecting around 835 people. Tidal flooding in Bima Regency in West Nusa Tenggara Province June 14 submerged around 50 homes and affected nearly 2,000 people. Heavy rainfall in Musi Banyuasin Regency in South Sumatra Province June 14 caused the Sake River to overflow, triggering flooding that affected over 1,500 people.

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 regional airports. 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