SINGAPORE — The strong, gusty winds felt across Singapore on Monday (Jan 18) are due to the northeast monsoon surge and are not unusual for this time of the year, said weather experts.

According to the Meteorological Service Singapore, wind speeds reached a high of 49.3km/h at the Admiralty weather station at 11.01am, the highest on Monday. The Tai Seng weather station recorded wind speeds of 37.2 km/h at about 2pm.

Above-average wind speeds are typical for this time of the year when the overall flow is dominated by northeast monsoon winds, said Dr Matthias Roth, an urban climatology professor at the National University of Singapore.

“Generally high wind speeds also create strong gusts,” he told CNA.

There is currently a “strong high pressure system” over China, creating a surge of northeast winds over the South China Sea. This is responsible for the windy weather, but also the cool and rainy conditions Singapore is experiencing, he added.

The blustery gales will last as long as the current conditions over China exist, said Dr Roth, “probably just a couple of days at most”.

The strongest winds occur during the northeast monsoon in January and February, said Professor Benjamin P Horton, director of the Earth Observatory of Singapore at the Nanyang Technological University.

Winds in Singapore are “generally light”, with mean surface wind speed normally at less than 2.5 m/s. During a northeast monsoon surge, mean speeds of 10 m/s or more have been observed, he added.

The strongest wind gust recorded in the last 36 years was on Nov 29, 2010, when the maximum wind speed hit 90.7km/h.

“The other times when strong winds occur are during thunderstorms. Surface wind gusts are produced from thunderstorm downdrafts and from the passage of Sumatra squall lines,” said Prof Horton. 

The Sumatra Squall is an organised line of thunderstorms that develops over the Indonesian island of Sumatra and moves eastward toward Singapore and Malaysia. Such thunderstorms may last up to two hours and feature wind gusts of more than 80km/h, he added.

However, winds associated with the Sumatra Squall usually do not last long, unlike conditions brought about by the northeast monsoon.

"Given the large scale of the situation which causes the high background wind speed, gusts will be experienced across all of Singapore," said Dr Roth of the current windy weather.

"This is unlike the even stronger gusts associated with other well-known phenomena such as Sumatra Squalls which, however, are less common during the northeast monsoon period, and are local in nature and usually don’t last long."

He added that the urban environment plays a part.

“While higher average wind speeds usually create stronger gusts, this relationship is modified in cities where friction by buildings can result in very strong localised gusts in response to the street network,” said Dr Roth.

"Hence, even in a seemingly sheltered environment near the surface, a pedestrian may find strong gusts in some places.”

The Met Service said on Friday that Singapore can expect fair and occasionally windy conditions on a few days in the second half of January, with stable atmospheric conditions arising from the presence of a dry air mass over the equatorial Southeast Asia region. CNA

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