Jakarta. Recent floods and landslides in Sumatra are a sign that Indonesia can no longer claim to be beyond the reach of tropical cyclones, a climate expert has warned, citing shifting storm patterns in Southeast Asia.

Erma Yulihastin, senior climate researcher at the National Research and Innovation Agency (BRIN), said changes in storm behavior now make tropical cyclones capable of making landfall and causing destructive impact in Indonesia — something long believed to be geographically impossible.

“For years we assumed Indonesia was safe because it lies on the equator, where storm rotation weakens naturally,” Erma said in a recent interview. “That’s not the case anymore. Indonesia is no longer free from tropical cyclones.”

She pointed to Cyclone Seroja (2021), which devastated areas of East Nusa Tenggara, and Cyclone Senyar (2025), which caused severe fatalities in Sumatra, as evidence that landfalling cyclones are now a real threat.

Erma said early warning signs must be taken seriously, particularly in high-risk areas such as the western coast of Sumatra and Nusa Tenggara. Persistent heavy rain lasting several days can serve as a precursor before a cyclone forms. She urged stronger storm literacy and investment in science-based prediction systems to better prepare communities.

Meanwhile, the Meteorology, Climatology, and Geophysics Agency (BMKG) confirmed that the tropical cyclone behind recent extreme weather has moved away from Indonesia. However, the agency warned that other atmospheric dynamics could still trigger intense rainfall.

Indonesia is now entering the monsoon phase, marked by increased moisture flow from the Indian Ocean, said BMKG Deputy for Meteorology Guswanto.

“The cyclone has moved away, but we must remain alert as the monsoon becomes stronger in mid-December,” he said.

BMKG is also monitoring the Madden-Julian Oscillation (MJO), a global atmospheric wave that can enhance raincloud development. MJO activity is expected to strengthen between the second and third week of December, increasing the chance of moderate to heavy rainfall in many regions.

With unstable atmospheric conditions, BMKG urged regional governments and the public to heighten preparedness, particularly in flood- and landslide-prone areas. The public is advised to monitor official forecasts and early warnings issued by the agency.