BMKG: Australian Monsoon Strengthens Again in Recent Days

Indonesia's Meteorology, Climatology, and Geophysics Agency (BMKG) has observed a recent strengthening of the Australian Monsoon. This eastward monsoon wind typically carries dry air masses into parts of Indonesia, marking the transition to the dry season. The agency's latest analysis, as of June 1, 2026, indicates that this monsoon surge has reduced cloud formation, particularly from morning to afternoon, leading to more optimal sunlight penetration to the surface.

During the period of May 29-31, 2026, maximum air temperatures exceeding 35.0 to 36.4 degrees Celsius were recorded in several regions, including North Sumatra, Riau, South Papua, Banten, and Central Sulawesi. However, BMKG notes that even with the recent strengthening, the Australian Monsoon remains weaker than its normal intensity. This weaker state allows for continued rainfall in certain areas, primarily in western and eastern Indonesia.

Notable rainfall amounts were recorded, with Maluku receiving the highest at 102.5 mm/day, followed by Central Sulawesi at 70.5 mm/day. Jakarta also experienced significant rainfall, recording 70.4 mm/day on Saturday, May 30, 2026, which is classified as heavy rain. Besides the weaker-than-normal monsoon, these significant rain events are also influenced by atmospheric dynamics that support the growth of rain clouds.

Specifically, the Equatorial Rossby Waves and Kelvin Waves are actively observed across parts of Sumatra, Kalimantan, Sulawesi, North Maluku, Maluku, and Papua. Additionally, Tropical Cyclone Jangmi, which developed from Tropical Depression 99W near the Philippines north of Papua, is indirectly affecting weather in eastern Indonesia. This cyclonic system influences surrounding air currents and contributes to increased potential for rain cloud development in adjacent areas.

Looking ahead to the next week, BMKG's analysis of global climate indicators points to El Niño conditions in the Pacific Ocean. These conditions are generally expected to decrease rainfall potential across most of Indonesia. Nevertheless, regional atmospheric dynamics may still foster rain cloud development in some areas, particularly in northern and eastern Indonesia. The Madden-Julian Oscillation (MJO) is predicted to be in phases 7 (Western Pacific) and 8 (Western Hemisphere and Africa), which have less influence on Indonesia. However, the Kelvin Wave is expected to remain active in several regions, including northern Sumatra, the southern coast of Java, Bali, West Nusa Tenggara, East Nusa Tenggara, West Kalimantan, northern and central Sulawesi, North Maluku, and Southwest Papua, potentially supporting rain cloud growth.