These Two Rare Phenomena Cause Persistent Rain in Indonesia

Heavy Rain

Despite the approaching dry season, Indonesia is still being heavily soaked by the rainy season, and experts have identified two climate phenomena as the major cause of this persistent rain.

Erma Yulihastin, a Climate Researcher at the Climate and Atmosphere Research Center of the National Research and Innovation Agency (BRIN), explained that the heavy rain hitting most of Indonesia in early March is triggered by two important factors: Cross Equatorial Northly Surges (CENS) and Borneo Vortices or storms.

CENS is a strengthening of north winds with an average speed of more than 5 meters/second in the southern part of the South China Sea near the Java Sea.

The CENS index has been active since February 21. This strong north wind has played a role in strengthening the monsoon wind up to 2-3 times its original strength, affecting the strong winds that are currently prevalent.

Borneo Vortices are wind swirls that have rotation radii on a meso scale, ranging from tens to hundreds of kilometers. Both factors interact continuously at the same location, making them stronger and larger.

If there is a continuous formation of CENS or cold surges and they interact with the Borneo vortex, which continuously rotates at the same location, and lasts for more than 72 hours or four days, then a tropical cyclone is formed.

Erma referred to a study conducted by Chang et al. from the Department of Meteorology, Naval Postgraduate School, Monterey, California, USA (2003) on the formation of Typhoon Vamei in the equator near Singapore-Batam on December 27, 2001.

She said that this event is very rare, and the probability of it happening again is about 100-400 years, as not all requirements may be fulfilled. in conclusion, those two rare phenomena caused persistent rain in Indonesia.

Meanwhile, the Meteorology, Climatology, and Geophysics Agency (BMKG) has warned that several regions of Indonesia have the potential to experience heavy rainfall on 1-2 March.

Sumatra is generally predicted to experience light rain, while Lampung, Bengkulu, South Sumatra, Jambi, West Sumatra, Riau, Riau Islands, and Aceh have the potential for heavy rain.

Java is generally predicted to experience light rain, with Banten potentially experiencing moderate rain, and East Java, Central Java, and West Java potentially experiencing heavy rain.

The Bali region, NTB, and NTT have the potential to experience light to heavy rain. Kalimantan is generally predicted to be cloudy, with Central Kalimantan and West Kalimantan potentially experiencing heavy rain.

Most of Sulawesi is expected to be cloudy, but South Sulawesi, Southeast Sulawesi, West Sulawesi, and Central Sulawesi have the potential for heavy rain, and the Maluku and Papua regions have the potential for light to heavy rain.

BMKG also mentioned that the wind speed in several regions affected by rain reaches 20 to 30 km/h from the West.