Cyclone Senyar is rare for S-E Asia; could such a storm ever hit S’pore?

Tropical cyclones need a spinning force to form but that force is weak over the Equator

- Ang Qing and Shabana Begum

Since late November, floods and landslides have swept Southeast Asia, claiming close to 900 lives and displacing many from their homes.

The region usually experiences a rainy season at the end of the year. But this time, other than the lashing rains, worry had swirled over a cyclone called Senyar that developed over the usually calm Malacca Strait.

This is a rare occurrence, as such rotating storms hardly happen along the Equator.

The Straits Times unravels the science behind the unusual cyclone that resulted from a confluence of weather events, and looks at how likely it is for Singapore to be hit.

Q What are tropical cyclones?

A These are powerful storms that draw heat from warm water at the ocean’s surface to power horizontal, rotating winds, according to NASA.

Typhoons, cyclones and hurricanes are the same phenomenon, but have different names depending on where they form.

They are called hurricanes when they develop over the north Atlantic Ocean, central-north Pacific, and eastern-north Pacific. They are known as cyclones when they form over the south Pacific and Indian Oceans.

Dr Koh Tieh Yong, a member of the Working Group on Asian-Australian Monsoon under the World Climate Research Programme, said only the strongest tropical cyclones formed in the northwest Pacific Ocean, including the South China Sea, are called typhoons.

“Senyar was not formed in the northwest Pacific and was not strong enough in any case to be called a typhoon,” said Dr Koh. Such storms are considered typhoons only when wind speeds reach about 119kmh.

Q Why is it rare for tropical cyclones to occur near the Equator, where Singapore is?

A Since records began, only two such cyclones have happened.

Typhoon Vamei developed in 2001 about 150km north of Singapore.