Andrew Tito, Jakarta – The Meteorology, Climatology, and Geophysics Agency (BMKG) has warned that significant weather events are likely to continue across the country in the coming days, following heavy to extreme rainfall that hit regions including Jakarta, Banten, West Java, and South Sumatra in the last four days.
BMKG urged the public to stay vigilant and take precautionary measures to reduce the risk of hydrometeorological disasters, such as floods, flash floods, water pooling, and landslides. "Residents are advised to protect themselves, their families, and their communities," the agency said via its official Instagram account.
According to BMKG, the extreme rainfall last week and the forecast for the coming week are influenced by several global and regional atmospheric factors. A primary driver is the El Nino – Southern Oscillation (ENSO), currently in a negative phase, known as La Nina, which is characterized by cooler-than-normal sea surface temperatures in the central and eastern Pacific Ocean. While classified as weak, the current La Nina increases atmospheric moisture, contributing to heavier cloud formation and rainfall, particularly in eastern Indonesia.
The Asian Monsoon is also active and expected to persist until early February 2026. This monsoon flows from the Asian continent toward Indonesia, bringing humid air masses that increase the likelihood of intense rainfall, especially in Jakarta and surrounding areas.
Another contributing factor is the Cross Equatorial Northerly Surge (CENS), where winds from the South China Sea cross the equator and strengthen moisture supply over the archipelago. Low-pressure systems in regions such as the Indian Ocean south of Banten, the Gulf of Carpentaria, and northwestern Australia further slow wind speeds over southern Indonesia, enhancing conditions for moderate to heavy rainfall.
Meanwhile, the weakening Tropical Cyclone Luana has transitioned into a low-pressure system, continuing to support the formation of elongated cloud patterns that exacerbate rainfall. High atmospheric moisture and strong atmospheric instability – conditions that favor rapid cloud convection – have intensified the potential for heavy rain across southern Indonesia.
Forecast for the coming week
BMKG forecasts very heavy to extreme rainfall in parts of West Java, Sumatra, East Java, Nusa Tenggara Timur, Kalimantan Barat, Sulawesi Selatan, and the Papuan highlands. Moderate rainfall is expected in many other provinces, including Jakarta and surrounding areas. Strong winds are forecast in parts of Bali, Nusa Tenggara, Kalimantan, Sulawesi, Maluku, and southwestern Papua.
For the Greater Jakarta Aera, heavy rainfall is predicted in central, west, east, and north Jakarta, as well as parts of Bekasi, Bogor, Tangerang, and Tangerang Selatan at various points through Feb. 2. Residents are advised to monitor local forecasts daily.
BMKG emphasized that the convergence of atmospheric phenomena – including La Nina, the Asian Monsoon, CENS, and low-pressure systems – has amplified moisture and instability, driving extreme rainfall events. The agency warned that these conditions could continue to trigger hydrometeorological hazards such as floods, landslides, and flash floods.