Why it rains despite drought and strong El Niño

Indonesia is experiencing a paradoxical weather situation, with heavy rainfall occurring in some regions despite a prevailing dry season and a strengthening El Niño. Between July 27 and 29, several areas recorded significant precipitation, including West Sumatra (126 mm/day), Riau Islands (97 mm/day), Aceh (83.5 mm/day), West Java (53.4 mm/day), and North Sumatra (52.6 mm/day).

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Negative anomalies in Outgoing Longwave Radiation (OLR) during the same period also indicate an increase in cloud cover that supports the potential for rain cloud formation in these areas.

The Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG) explained that these localized rains are supported by the activity of Kelvin and Rossby Equatorial waves, which influenced western and central parts of the archipelago. Negative anomalies in Outgoing Longwave Radiation (OLR) also indicated increased cloud cover conducive to rain formation in these areas.

However, the agency cautioned that global climate developments suggest dry conditions will continue to dominate most of Indonesia in early August. The El Niño phenomenon remains strong, with the Nino 3.4 index at +2.26 degrees Celsius, and is expected to intensify further. This condition typically suppresses cloud formation and reduces rainfall across the country.

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The climate development in the period of July 31 – August 6, 2026, still shows conditions that support the continuation of dry weather in Indonesia.

According to the BMKG's forecast for the first ten days of August, low rainfall categories are predicted for approximately 91.43% of Indonesia, with only 8.57% expected to experience moderate rainfall. No regions are predicted to have high or very high rainfall.

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This phenomenon has the potential to reduce the formation of rain clouds and suppress rainfall in various regions.

Despite the overall dry outlook, the agency noted that the influence of the Rossby and Kelvin Equatorial waves, along with the potential impact of a tropical cyclone 'seed' (94W) in the Pacific Ocean north of West Papua, could still lead to localized rain. These atmospheric phenomena can create conditions for air mass convergence, potentially resulting in light to heavy showers in affected areas.

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Light to heavy rain is still possible locally, especially in areas affected by atmospheric waves, tropical cyclone seeds, as well as convergence and confluence areas.