Extreme Weather Threatens Jakarta And West Java, Government Performs Controlled Rain Operations

Proses pengangkutan bahan semai NaCl ke dalam badan pesawat Caravan di Lanud Halim Perdanakusuma, Jakarta, Kamis (10/7/2025) (dok BNPB)

JAKARTA The Weather Modification Operation (OMC) held by the National Disaster Management Agency (BNPB) has entered its fourth day on Thursday, July 10, 2025. During this period, as many as 16 tons of material Semai had been deployed into the atmosphere through 18 flight sorties to reduce the impact of extreme weather that hit West Java and Jakarta.

Of the total material in semai, 12.4 tons are Sodium Choride (NaCl), while the other 3.6 tons are Calium Oksida (CaO). Two Caravan aircraft with registration numbers PK-DPI and PK-SNL were alerted at Halim Perdanakusuma Air Base, Jakarta, and were used alternately in the air operation.

Head of the BNPB Disaster Data, Information and Communication Center, Abdul Muhari, explained that the seeding was carried out for 24 hours periodically in the North and South Coast areas of West Java. The main focus is in the waters north of Karawang, Bekasi, Indramayu, and the upstream area of the river which leads to flood-prone areas in Jabodetabek.

"This operation is to anticipate and reduce the intensity of extreme rain by diverting rain to the sea, before the clouds move to the mainland," said Abdul Muhari, Friday, July 11.

Technically, NaCl is used to trigger cloud condensation and accelerate the formation of rain, while the Oxide Calcium is used to increase the intensity of rainfall at certain points, as part of a directed rain redistribution effort.

This OMC was carried out as an emergency step by the government in response to the wet dry season which triggered extreme weather in a number of Javanese areas. The operation was carried out by BNPB with the support of the Meteorology, Climatology and Geophysics Agency (BMKG) and the Indonesian Air Force.

The operation is planned to last for five days, from Monday to Friday, July 7, 2025, in a quick response to high-intensity rain that flushed most of the western region of Java on Sunday, July 6, 2025, causing flooding in various locations.

With this modification of the weather, the government hopes that the potential for heavy rain that is still expected to occur in the first basis of July can be suppressed, so that the risk of flooding in densely populated areas and disaster-prone areas can be minimized.