What's a Sumatra squall and how does it affect Singapore?

Thundery showers and gusty winds on Sept 17 caused by such a storm

- Fatimah Mujibah

The storm that swept into Singapore on Sept 17 lasted barely an hour, but left its mark across the island.

From Tampines in the east to Mount Faber in the south and Yishun in the north, netizens took to Facebook, Instagram and TikTok to document felled trees and broken branches strewn over roads.

There were also other unusual incidents, such as a pair of trousers seen flying among high-rise buildings, pool furniture flying across and landing in the pool and various tableware pieces flying at an outdoor restaurant as patrons attempted to enjoy their meal.

Malaysia and Brunei were also affected by the extreme winds and rainfall. The Malaysian island of Penang had more than 200 toppled trees over two days from Sept 15, while Brunei's fire and rescue department personnel attended to 72 emergency calls over fallen trees and 20 calls over roofs blown off on Sept 17.

In a statement on Sept 18, the National Environment Agency's Meteorological Service Singapore (MSS) confirmed that the widespread thundery showers and gusty winds on Sept 17 were caused by a Sumatra squall.

The squall had developed over the Strait of Malacca and swept across the island rapidly from about 7pm to 8.30pm, with East Coast Park recording the highest wind gust of 83.2kmh at 7.33pm.

The Straits Times looks at what Sumatra squalls are, how this weather phenomenon affects Singapore and the rest of South-east Asia and if Singapore can expect to see more of such weather in the upcoming months.

WHAT ARE SUMATRA SQUALLS AND WHAT CAUSES THEM?

Sumatra squalls are a common and vigorous line of thunderstorms travelling rapidly towards the South China Sea.