BMKG Reveals Triggers for Heavy Rain Haunting Jabodetabek Ahead of Dry Season Entry
Weather forecaster from BMKG, Wahyu Argo, stated that the recent rains do not immediately signal a change in the dry season timeline. He explained that the onset of the dry season occurs gradually and not simultaneously across all regions.
Based on BMKG’s predictions, parts of Indonesia, including portions of Jakarta, Banten, West Java, Central Java, Yogyakarta, and East Java, are forecasted to begin entering the dry season during the period of May II-III 2026.
“Meanwhile, rainfall from May to October 2026 is generally predicted to be in the low to moderate category,” said Wahyu to reporters on Tuesday (5/5/2026).
Nevertheless, Wahyu clarified that during the transition to the dry season or its early phase, local rain remains possible. In particular, he added, if daily atmospheric conditions still support the development of rain clouds.
“Heavy rain with moderate to intense intensity still occurring in Indonesian regions, including Jabodetabek, is influenced by a combination of global, regional, and local atmospheric factors,” he stated.
He mentioned that in recent days, atmospheric disturbances such as the Madden-Julian Oscillation (MJO) in phase 2 have been observed, supporting increased rain cloud formation in western Indonesia. Additionally, Wahyu said, the activity of other atmospheric waves like Equatorial Rossby, Kelvin, and Mixed Rossby-Gravity can modulate convective processes in parts of Indonesia, including Java.
“These conditions are reinforced by sufficiently high air humidity and local atmospheric lability, allowing convective clouds to grow rapidly and produce rain with moderate to heavy intensity, even though some areas have begun entering the early dry season period,” he explained.
Wahyu noted that the weather pattern changing rapidly from intense heat during the day followed by heavy rain in the afternoon to evening is still common during the seasonal transition period. He said strong solar heating from morning to midday can trigger evaporation and increase local cloud formation.
“If at the same time the atmosphere is still sufficiently moist and unstable, and supported by atmospheric disturbances, moderate to heavy rain can occur in a relatively short duration. This condition is not always uniform across all areas and its timing can vary, depending on daily atmospheric dynamics,” said Wahyu.