BMKG Warns of El Nino Impact as Heavy Rain Persists

TEMPO.CO, Jakarta - The Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG) stated that weather conditions in Indonesia are still exhibiting typical transitional dynamics over the past few days. Reduced cloud cover from morning to afternoon in several areas has intensified surface heating, resulting in warmer daytime temperatures.

Hot daytime temperatures can support the formation of rain clouds, especially in the afternoon and evening. This opportunity is generally greater in areas with sufficient air humidity, as atmospheric conditions favor the growth of convective clouds.

This is confirmed by the continued heavy to extreme rainfall recorded in several areas. For example, the BMKG recorded extreme daily rainfall in Bogor, West Java, reaching 184.5 mm throughout last Friday, May 15, 2026.

The increased chance of rain is influenced by a combination of several active atmospheric dynamics, including the Madden-Julian Oscillation (MJO), Equatorial Rossby Waves, Kelvin Waves, and Mixed Rossby-Gravity (MRG). Furthermore, there is the presence of cyclonic circulation in several areas.

El Nino Conditions Ahead

For the week ahead, May 19 to 25, 2026, the Meteorology, Climatology, and Geophysics Agency (BMKG) has revealed that Indonesia is already in the El Nino condition category. The Nino index is +0.52, meaning sea surface temperatures in the central-eastern equatorial Pacific Ocean have warmed by 0.52 degrees Celsius compared to normal.

"This value indicates a potential decrease in rain cloud formation activity in Indonesia, especially in the eastern part," read a statement issued by the BMKG's Directorate of Public Meteorology on Monday, May 18, 2026.

However, according to the same statement, Madden-Julian Oscillation (MJO) activity is predicted to remain in phase 3 in the Indian Ocean, resulting in an active spatial filter over most of Indonesia. This means there is still potential for increased convective cloud formation in several regions of Indonesia despite the El Nino conditions.

Over the next week, atmospheric conditions in Indonesia are also predicted to be influenced by several tropical wave activities and cyclonic circulation. "The combination of tropical wave activity, circulation patterns, wind deflection and deceleration, and convective activity, supported by sufficient humidity, has the potential to support rain cloud growth in affected areas."

Several regions remain on Alert status for the next week. They still have the potential to experience heavy to very heavy rainfall between May 19-25. These include West Java and several areas in Sulawesi.

Separately, in the Atmospheric Dynamics Analysis for the First Decade of May 2026, the Meteorology, Climatology, and Geophysics Agency (BMKG) issued an early warning of meteorological drought in the second decade of May, with a Warning level. This area covers several regencies/cities in the provinces of West Sumatra and South Sumatra.

The Indian Ocean Dipole index remains neutral. As predicted, a super-intense El Nino will occur this year. The effects of the drought in Indonesia will be further amplified by a positive IOD, which has similar effects to El Nino, only originating from the Indian Ocean.

Read: El Nino Could Trigger Extreme Fires Worldwide in 2026

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