Observing the 2025 Wet Drought Phenomenon

Unlike last year's drought, Indonesia will experience a wet drought this year. What will be the impact on several sectors of community life in Indonesia?

The Meteorology, Climatology, and Geophysics Agency (BMKG) predicts that most regions of Indonesia are currently entering the transitional season. BMKG reported that 57.7 percent of the area or 403 seasonal zones (Zom) in Indonesia will enter the dry season during the period from April to June.

The transitional season is the period between the rainy season and the dry season. During this period, the weather can change rapidly, characterized by hot air and weather in the morning to afternoon, followed by rain from afternoon to evening.

The Meteorology, Climatology, and Geophysics Agency (BMKG) in an information update on Monday (5/5/2025) stated that the peak of the dry season is expected to occur in August. It is even predicted to last the same or potentially arrive earlier than usual, dominating the entire region of Indonesia. Compared to the normal period, the duration or period of the dry season this year is predicted to be shorter than usual in 298 zones or 43 percent of the area.

Although the calendar has marked the arrival of the dry season, several regions in Indonesia are still experiencing rainfall. This phenomenon is certainly not without reason. The Meteorology, Climatology, and Geophysics Agency (BMKG) states that Indonesia is currently undergoing a wet dry season.

The unusual characteristics of this year's dry season are reflected in the consistently high rainfall in several regions, even though, according to the calendar, the season has entered the dry period.

The Meteorology, Climatology, and Geophysics Agency (BMKG) stated that this year's wet drought is not influenced by global climate conditions, such as the El Nino-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), which are currently in a neutral phase. This phenomenon is more likely influenced by the warming of Indonesia's sea surface temperatures, which is expected to persist until September.

The current anomaly of the wet dry season does not mean that it is a new phenomenon for Indonesia. Data from BMKG indicates that the wet dry season has occurred several times in the last decade, including in 2010, 2013, 2016, 2020, 2023, and is now indicated to reappear in 2025. The pattern shows a trend of increasing frequency and longer duration.

In 2016, most regions of Indonesia had not entered the dry season until June and still experienced high rainfall. This phenomenon occurred again in 2020, where the dry season was wetter than the previous year.

This year, the Meteorology, Climatology, and Geophysics Agency (BMKG) predicts that the wet drought phenomenon affecting several regions in Indonesia will last until August 2025. This means that the community will still face rainfall even though the calendar has already entered the dry season.

A wet drought is an unusual meteorological condition. According to BMKG, a wet drought is a condition in which the dry season is still characterized by significant rainfall. Typically, the dry season is marked by hot weather and clear skies. However, during a wet drought, humidity remains high, allowing for more frequent rainfall.

The phenomenon of the wet dry season is characterized by high humidity and still significant rainfall during the transitional period until the beginning of the dry season. This has also been noted by the Meteorology, Climatology, and Geophysics Agency (BMKG), particularly for regions with monsoonal rainfall patterns or areas that have a clear distinction between the rainy and dry seasons, such as Java, Bali, and Nusa Tenggara.

The causes of this phenomenon are quite complex and influenced by several atmospheric phenomena in the region of Indonesia. Observations by the Meteorology, Climatology, and Geophysics Agency (BMKG) on Thursday (15/5/2025) revealed that a cyclone circulation is predicted to form in several areas, such as the Indian Ocean southwest of Sumatra, the Makassar Strait, the waters north of North Maluku, Maluku, and the waters north of West Papua. This phenomenon creates a convergence area from the western point of Indonesia to West Papua.

BMKG also noted other atmospheric dynamics. The Madden-Julian Oscillation (MJO) phenomenon, Kelvin waves, Equatorial Rossby waves, and low frequency waves that were actively monitored became a combination of phenomena that have the potential to increase convective activity and cyclonic formation in the region. The impact of these atmospheric dynamics also has an influence on the potential for rain in some parts of Indonesia.

According to the Meteorology, Climatology, and Geophysics Agency (BMKG), the Madden-Julian Oscillation (MJO) is a natural phenomenon that affects weather in tropical regions, particularly in Indonesia, with a period of 30-60 days. The MJO is a wave or oscillation that moves from west to east, from the Indian Ocean to the Central Pacific Ocean, and brings changes in rainfall.

Atmospheric Kelvin waves are a system of tropical precipitation accompanied by characteristic west and east wind patterns. These waves move eastward around the Earth and can encircle tropical regions for a month.

Meanwhile, the Equatorial Rossby wave is a phenomenon that occurs in fluids (atmosphere/ocean) that rotate in pairs and move westward around the equatorial region. Rossby waves are also known as planetary waves.

This phenomenon does not occur uniformly across all regions of Indonesia. The Meteorology, Climatology, and Geophysics Agency (BMKG) noted on Thursday (15/5/2025) that several areas, such as Java, Bali, Nusa Tenggara, Central Sulawesi, Maluku, and Papua, will experience heavy rain and the potential for strong winds from May 16 to 22, 2025. Under normal conditions, these regions typically experience one peak of rainfall and one peak of drought. However, this year, that pattern has been disrupted as rain continues to fall during the dry season.

The Meteorology, Climatology, and Geophysics Agency (BMKG) predicts that the wet drought will cause the community to continue facing rain even though the dry season has begun. BMKG projects that the wet drought phenomenon will last until the end of the dry season in August 2025.

After that, Indonesia will enter the transitional season or the change of seasons between September and November 2025, and the rainy season will return in December 2025 until February 2026.

The phenomenon of the wet drought occurring this year certainly has the potential to impact various sectors of community life, ranging from the environment, agriculture, health, to the daily activities of the populace.

In the environmental sector, although the intensity of rainfall is not as heavy as during the rainy season at the beginning of this year, the potential for disaster remains a threat. High rainfall during the dry season can trigger local flooding or landslides, especially in areas that are vulnerable and unprepared to face this weather anomaly.

Dense urban areas become prone to flooding during prolonged heavy rainfall, especially in regions lacking adequate drainage systems. This is not only applicable during the rainy season; the transitional season and this year's wet dry season also contribute to the increased potential for flooding and inundation disasters.

For example, several areas in Jakarta, Bogor, Depok, Tangerang, and Bekasi (Jabodetabek) were inundated with floods following the rain that poured down from Tuesday night, May 13, to Wednesday, May 14, 2025.

In the agricultural sector, a wet drought can be a double-edged sword. On one hand, high rainfall intensity leads to abundant water reserves during the dry season, which can be utilized by farmers to expand their land and increase rice production. On the other hand, it raises the risk of waterlogging in rice fields or even increases the risk of flooding in river flows that affect the surrounding rice paddies.

The increase in sea surface temperatures during this dry season is likely to have a positive impact on the capture fisheries sector. The cold conditions of the eastern Pacific Ocean will encourage tuna to move into the warmer waters of Eastern Indonesia, thereby increasing the income of fishermen.

Furthermore, in certain plantation sectors, this wet dry season is likely to have adverse effects. High rainfall intensity has the potential to reduce the production yields of several plantation commodities, such as tobacco, sugarcane, and tea, as well as other horticultural crops, which could be detrimental to farmers.

From a health perspective, the wet dry season opens up opportunities for the emergence of diseases that typically spread during the rainy season, ranging from dengue fever to respiratory illnesses, such as acute respiratory infections. Prolonged stagnant water can become a breeding ground for mosquitoes. Additionally, extreme temperature fluctuations between day and night can also affect the body's immune system.

Finally, this phenomenon of wet drought can serve as a reminder that climate change is increasingly felt in Indonesia. Its impacts are varied, ranging from drought to natural disasters. Therefore, it is necessary to enhance awareness and concern for the environment.

In addition, the government also needs to formulate strategies for mitigation and adaptation to climate change and increasingly unpredictable weather patterns.

(Kompas Research and Development)