Rain in Various Regions Impact of Transition Pattern to Dry Season

JAKARTA, KOMPAS – In recent days, rain with light to heavy intensity has frequently occurred in various regions in Indonesia, including the areas of Jakarta, Bogor, Depok, Tangerang, and Bekasi, collectively known as Jabodetabek. The weather dynamics in most parts of Indonesia still indicate a transition pattern from the rainy season to the dry season.

The Director of Public Meteorology at the Meteorology, Climatology, and Geophysics Agency (BMKG), Andri Ramdhani, stated that based on the latest climatological analysis for the second dekad of May 2025, only 11 percent of the seasonal zones in Indonesia have entered the dry season. Meanwhile, 73 percent of the seasonal zones are still in the rainy season.

"This indicates that almost the majority of regions in Indonesia are still in the transition period from the rainy season to the dry season," he stated in an official statement on Friday (23/5/2025).

The weather dynamics in most regions of Indonesia indicate a transition pattern from the rainy season to the dry season, commonly known as the transitional period. During this period, the weather tends to be clear in the morning until early afternoon, then changes to rain accompanied by thunderstorms in the afternoon to evening.

This rain is not only caused by local convective mechanisms that often occur during transitional periods, but is also influenced by broader atmospheric dynamics. These atmospheric dynamics include the activity of the Madden-Julian Oscillation (MJO), the active presence of equatorial Rossby and Kelvin waves, as well as tropical disturbances in the southwest of Bengkulu.

From the analysis of BMKG, the MJO is currently observed to be spatially active in the southern region of Indonesia and is predicted to remain consistently in that area for the next few days. The Kelvin and Equatorial Rossby waves are also likely to persist in some regions of Indonesia for the upcoming week.

These phenomena have the potential to have a significant influence in triggering increased growth of rain clouds, especially in the southern and central parts of Indonesia.

Almost all of Indonesia is still in the transition period from the rainy season to the dry season.

Meanwhile, the circulation of the Cyclonic system is predicted to be located in the waters west of Lampung, the Java Sea, the Sulawesi Sea, and the Seram Sea, forming a converging area extending in the Indian Ocean west of Lampung. This condition also has the potential to cause an increase in rainfall as one of the indicators of extreme weather events.

On the other hand, the movement of dry air masses from the Australian continent continues to indicate a decrease in rainfall in several areas as the dry season sets in. This triggers an increase in wind speed in the southern regions of Indonesia, as well as a rise in wave height in the Indian Ocean from the southwest of Lampung to the south of East Nusa Tenggara.

Regarding the weather prospects for the upcoming week, the Meteorology, Climatology, and Geophysics Agency (BMKG) predicts that the weather in Indonesia during the period of May 23-29, 2025, will generally be dominated by overcast conditions with light rain. However, it is also necessary to be vigilant about the potential increase in moderate rainfall occurring in several regions.

In addition, several regions still have the potential to experience heavy to extreme rainfall, which may be accompanied by lightning or thunder and strong winds. These regions include, among others, North Sumatra, Lampung, Central Java, West Java, Yogyakarta, East Java, East Kalimantan, North Kalimantan, Maluku, and South Papua.

Previously, the Head of BMKG, Dwikorita Karnawati, stated that the beginning of the dry season in 2025 started in April and will occur gradually in various regions of Indonesia. However, the dry season in 2025 is predicted to be shorter than usual in most parts of Indonesia.

"The beginning of the dry season in Indonesia is predicted not to occur simultaneously. In April 2025, a total of 115 seasonal zones will enter the dry season. This number will increase in May and June, as the affected areas expand, including most of Java, Bali, Nusa Tenggara, Kalimantan, and Papua," he stated.

Global climate phenomena such as the El Nino-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are currently in a neutral phase. This indicates the absence of significant climate disturbances from the Pacific Ocean or the Indian Ocean until the second semester of 2025.

Nevertheless, sea surface temperatures in the Indonesian region tend to be warmer than normal. This condition is expected to persist until September, which may affect local weather in Indonesia.

The Meteorology, Climatology, and Geophysics Agency (BMKG) predicts that the peak of the dry season will occur from June to August 2025. Several regions, such as Central to Eastern Java, Kalimantan, Sulawesi, Bali, Nusa Tenggara, and Maluku, are expected to experience peak drought conditions in August.

Regarding the characteristics of the 2025 dry season, approximately 60 percent of the area is predicted to experience a normal dry season, 26 percent of the area will experience a wetter than normal dry season, and 14 percent of the remaining areas will be drier than usual.

"The duration of the dry season is predicted to be shorter than usual in most regions, although there are 26 percent of areas that will experience a longer dry season, particularly in parts of Sumatra and Kalimantan. Regions experiencing a wetter dry season could present opportunities to expand planting areas and increase production," said Dwikorita.