Jakarta, CNN Indonesia —
Rain still flushed parts of Indonesia, including in Jakarta and its surroundings, even though it is now entering the month August which should be included in the peak phase of the dry season. What caused it?
The Meteorology, Climatology and Geophysics Agency (BMKG) records in the last three days, heavy rain to extreme occurred in Maluku (205.3 mm/day), West Kalimantan (89.5 mm/day), Central Java (83 mm/day), and Jabodetabek (121.8 mm/day).
Guswanto, Deputy for BMKG Meteorology, revealed that rain in the dry season is still within normal limits, and is known as wet drought.
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“This is not an extreme anomaly, but the result of complex atmospheric dynamics,” Guswanto said when contacted CNNIndonesia.comWednesday (6/8).
He explained that one of the causes of rain in the dry season is Indian Ocean Dipole (IOD), or climate phenomena that occur in the Indian Ocean, are at a negative level (-0.6) and warm sea temperatures cause water vapor supply to increase. Therefore, he stressed that the rain that fell during the dry season was not influenced by La Nina's phenomenon.
In addition, the rain that occurred in a number of areas in early August was caused by a combination of several atmospheric factors.
FirstMadden-Julian Oscillation (MJO) waves that are active in the Sumatra region to western Java and increase the potential for the formation of rain clouds.
Second90S tropical cyclone seeds in the Southwest Indian Ocean Bengkulu triggered wind convergence along the island of Java, strengthening the growth of rain clouds.
ThirdWarm sea level (SST) in Indonesian waters increases the water vapor content in the atmosphere.
Fourthother atmospheric waves such as Kelvin, Rossby Equator, and Low-Frequency are also active and strengthen the convective process.
Previously, the Head of BMKG Dwikorita Karnawati also mentioned the results of monthly rainfall predictions showed the rainfall anomalies that had occurred since May 2025 will continue, with the above rainfall conditions normal in most of Indonesia until October 2025.
“The weakening of Australian monsoon associated with the dry season also causes sea level temperatures in southern Indonesia to remain warm and this contributes to the occurrence of rainfall anomalies,” Dwikorita said at an online press conference in early July.
Then, the active wave of Kelvin monitored crossed the north coast of Java, accompanied by a slowdown and wind turn in western and southern Java also triggered a buildup of air masses.
In addition, wind convergence and local atmospheric lability are also observed to accelerate the growth of rain clouds.
Based on the global climate, BMKG and several world climate centers predict ENSO (sea level temperature in the Pacific Ocean) and IOD (sea level temperature in the Indian Ocean) will remain in the neutral phase in the second semester of 2025.
That is, it can be ascertained that some parts of Indonesia will experience rainfall above normal than what should have occurred in the dry season or also called wet drought.
Deputy of the Ardhasena Sopaheluwakan Climatology Division confirmed the current weather conditions were still in accordance with the forecasts issued by BMKG last July.
“That's right, it is still according to predictions,” he said.
Expert Climatology of the National Research and Innovation Agency (BRIN) Erma Yulihastin in July also predicts that rainfall will continue to be high until August. According to him, rainfall in August will even be higher than July.
“Later August is twice the current rain. It will occur in the third dasarian. The third dasarian means the 21st to the end of August,” he said in a upload on social media X, Monday (7/7).
According to him, bad weather in the August period is likely to be more evenly distributed. He said Vortex would be closer to the territory of Indonesia and cause an increase in intensity twice as now.
“Therefore the government to prepare and mitigate floods expand in Jabodetabek, which has the potential to cause a loss of Rp2-10 trillion in the event of a flood for a week. The community to be vigilant, especially those who live around the watershed,” he said.
(lom/dmi)
