It Shouldn't Have Formed, BMKG-UNAND Investigates Stray Cyclone That Caused Days of Rain in Sumatra

PADANG – Andalas University (UNAND) is conducting special research on the unusual movement of tropical cyclones that have triggered hydrometeorological disasters in several areas of West Sumatra.

The Head of the UNAND Research and Community Service Institute (LPPM), Prof. Marzuki, said that his institution is collaborating with researchers from Poland, Brunei Darussalam, and the Meteorology, Climatology, and Geophysics Agency (BMKG) as data providers to investigate this unusual cyclone phenomenon.

Theoretically, he said, cyclones rarely form in areas near the equator, including West and North Sumatra. This is because several conditions for cyclone formation are not met, one of which is the Coriolis force, the force generated by the Earth's rotation.

"The further from the equator, the greater the Coriolis force. Meanwhile, at the equator, the Coriolis force is zero, so cyclones and other fluid rotation phenomena are very rare," he explained, as quoted by Antara, Monday, December 1.

However, the current phenomenon shows a different pattern. The cyclone actually formed in the relatively narrow Strait of Malacca, rather than over vast bodies of water like oceans, as tropical cyclones typically form.

Another difference highlighted was the formation of the cyclone at latitudes less than five degrees, whereas cyclones typically form at higher latitudes when the Coriolis force is strong enough.

"What's even more unusual is that this cyclone is moving closer to the equator. Most tropical cyclones actually move away from the equator," he said.

Although its intensity is weaker than large cyclones like those that typically hit the Philippines, its impact in Sumatra is significant. The cyclone's slow or almost stationary movement causes continuous rain to fall over the same area for several days.

Prof. Marzuki said this condition is one of the main questions in their research. "Why is the cyclone moving closer to the equator, even though it goes against its natural behavior? This research is expected to provide new insights into the world of atmosphere and climatology," he said.