Tropical cyclones almost never form over the Strait of Malacca. The narrow waterway separating the Malaysian peninsula from the Indonesian island of Sumatra is located so close to the equator that Coriolis effect usually too weak to allow storms to rotate enough to become cyclones. But on November 25, 2025, meteorologists watched as a tropical depression intensified into Cyclone Senyar—only the second documented instance of a tropical cyclone forming in the Strait.
Surrounded by land on both sides, Senyar made landfall on Sumatra later that day. made a U-turn and headed east towards Malaysia. As the slow-moving storm passed over Sumatra's mountainous terrain, many areas received nearly 400 millimeters (16 inches) of rain, the agency said. satellite estimates from NASA's Global Precipitation Measurement (GPM) mission. (Due to averaging of satellite data, local precipitation amounts may differ when measured from the ground.)
The flow caused widespread flash floods and landslides across Sumatra's rugged terrain. Streams and rivers quickly overflowed with muddy and debris that swept through villages, towns and cities. News reports say the damage has gotten worse earthquake struck on November 27, and an abundance loose piles of wood in a region that became a destructive battering ram in flood conditions. As of December 4, Indonesian authorities reported several hundred deaths and more than 700,000 displaced.
VAS-2 (Operational Land Imager-2) on Landsat 9 took this photo of flooding in Aceh and North Sumatra provinces on November 30, 2025. The dirty water, filled with sediment, appears to have inundated much of Lhoksukhon, a town of 40,000 people, and several surrounding villages.
Other tropical cyclones and monsoon rains that hit Sri Lanka, Thailand, Malaysia and Vietnam around the same time also caused widespread destruction in the wider region. According to one score The floods affected more than 10.8 million people in the region and displaced more than 1.2 million, according to the UN Office for the Coordination of Humanitarian Affairs.
NASA image taken by Lauren Dauphin of the Earth Observatory using Landsat data. US Geological Survey. Story by Adam Voyland.
- BNPB (2025) News index. As of December 4, 2025
- India Today (December 2, 2025) What made Cyclone Senyar a once-in-a-century weather event in the Strait of Malacca?. As of December 4, 2025
- Malaysian Nature Reserve (2025, December 3) Death toll from floods and landslides in Indonesia rises to 811. As of December 4, 2025
- NASA Earth Data (2025) Tropical cyclones. As of December 4, 2025
- New York Times (2025, December 3) Where flood waters turned piles of wood into floating battering rams. As of December 4, 2025
- ReliefWeb (December 3, 2025) Asia-Pacific: Humanitarian Review of Cyclones and Floods in Southeast and South Asia (17 November to 3 December 2025). As of December 4, 2025
- Research Center for Tsunami and Natural Disaster Mitigation (November 29, 2025) Extreme rainfall from Tropical Cyclone Senyar causes widespread flooding and infrastructure damage across Aceh. As of December 4, 2025
