Heavy Rain Warning for Several Regions in Indonesia This Week
Heavy Rain Warning for Several Regions in Indonesia This Week
Reporter
September 30, 2026 | 07:07 pm
TEMPO.CO, Jakarta - Indonesia’s Meteorology, Climatology and Geophysical Agency (BMKG) has issued an early warning for potential heavy to very heavy rain in several parts of the country over the next week.
According to BMKG’s weather forecast for September 29 to October 5, 2026, residents in Aceh, North Sumatra and West Java have been advised to remain alert for heavy to very heavy rain. Bengkulu is also under an alert for September 29 to October 1, while the warning applies to Papua Highlands from October 2 to 5.
Why Is Heavy Rain Expected?
BMKG said weather conditions across much of Indonesia from late September to early October would remain influenced by a very strong El Niño, although regional atmospheric dynamics could increase rain-producing cloud activity in some areas.
From September 27 to October 4, the Madden-Julian Oscillation (MJO) is forecast to move across the western Indian Ocean off Sumatra, affecting West Sumatra, the Mentawai Islands, Riau and South Sumatra.
Meanwhile, Equatorial Rossby and Kelvin waves are expected to be active simultaneously across parts of Sumatra and surrounding waters, including the waters north of Sabang in Aceh and the western Indian Ocean off Aceh.
Areas Affected by Atmospheric Waves
Across Bengkulu, Lampung, Banten, West Java, Jakarta, Central Java and waters off southern Central Java, Equatorial Rossby wave activity is expected to have a stronger influence.
These atmospheric waves can create conditions favorable for the growth of rain clouds in the areas they pass through.
BMKG also forecast slowing and shifting wind patterns in parts of Aceh, the Riau Islands, West Kalimantan, Central Kalimantan, East Kalimantan and West Papua. These patterns could increase the convergence of air masses and strengthen rain-cloud formation.
Local Atmospheric Conditions
At the local level, strong atmospheric instability is also expected in parts of northern and central Sumatra, West Kalimantan, Central Kalimantan, Central Sulawesi and parts of Papua.
Such conditions can intensify the upward movement of air and the development of convective clouds, particularly when sufficient moisture is available.
“Thus, although global climate dynamics generally continue to limit rain-cloud formation across much of Indonesia, regional and local atmospheric influences can still trigger increased rainfall activity in certain areas,” BMKG’s Directorate of Public Meteorology said in a statement released on September 28, 2026.
Read: BMKG Warns of Local Downpours Despite Dry Season
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