At least 1000 people are thought to have died, with more than 2700 more known to have been injured and more than 500 still missing after Cyclone Senyar swept across Sumatra and Peninsula Malaysia on 26-28 November 2025. The storm formed as a tropical depression in the Strait of Malacca on 22 November 2025, intensifying to become a tropical cyclone before making landfall on the northern part of Sumatra at about midnight on 26 November 2025. The storm moved southwards along the coast of North Sumatra, before sweeping back across the Strait of Malacca to make landfall on Peninsula Malaysia on 27 November. On 28 November the storm swept out over the South China Sea, where it dissipated several days later without making landfall again.
The passage of Cyclone Senyar resulted in at least 753 deaths on Sumatra, with a further 2600 injured and 526 people still missing, largely as a result of flooding and landslides. Over 1.2 million people on the island have been displaced because of the storm with about 3.3 million affected in some way, across the provinces of North Sumatra, West Sumatra, and Aceh. The storm is reported to have destroyed 3600 homes, and damaged a further 5800, along with 344 bridges and 324 schools.
The storm caused less damage in Peninsula Malaysia, where people had more time to prepare, with three fatalities, and 34 000 people evacuated from high-risk areas ahead of the storm. However, in neighbouring part of southern Thailand, flooding associated with the storm killed at least 267 people, with most of the fatalities occurring in Songkhla Province, according to government figures; although some sources have accused the government of downplaying the size of the disaster, with suggestions that more than 1000 people may have died in Songkhla Province alone. In addition, at least 102 people were injured, with two homes destroyed and 1074 damaged, along with 228 roads, 12 bridges, 41 schools and 38 temples. The city of Hat Yai in Sonhkla Province received 372 mm of rain on 21 November, more than is typical for the entire month of November, and more rain than has fallen on the city in a single day in 300 years of records.
Tropical storms, called Cyclones in the Indian Ocean and South Pacific, are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere. These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.
Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate 1 cm rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms.
However, Cyclone Senyar is unusual in that it formed in a part of the world not usually prone to tropical storms; it is only the first such storm ever to form in the Strait of Malacca, and the second to cross these waters, after Typhoon Vamei, which formed in the South China Sea in 2001, and crossed Peninsula Malaysia from east to west. This is because the Strait of Malacca is close to the equator, an area where it was once thought that tropical storms could not form, as the Coriolis Force is not strong enough. However, warming global sea temperatures appear to be making this possible, as more heat is effectively more energy, and this is the fifth such near-equator storm of 2025. This means that communities in these areas are not as used to tropical storms as communities in areas where they are a long-standing problem, and infrastructure has not typically been built with large storms in mind, greatly increasing the damage and casualties caused when they appear.
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