Last week’s cold spell was S’pore’s longest in a decade

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The cold spell experienced in the Republic last week was the longest here in at least a decade, records from the Meteorological Service Singapore (MSS) show.

"In the last 10 years, there was no cold spell of five days or more with minimum temperatures between 21 deg C and 22 deg C," the MSS spokesman told The Straits Times yesterday. "Over this period, most monsoon surges that affect Singapore are of short duration, lasting two to three days."

The five days of cool weather, which lasted from Wednesday to Sunday, were a result of a monsoon surge.

These surges, which are common in Singapore between December and March, are sudden increases in wind speed that cause cold air in the Northern Hemisphere to surge southwards into the South China Sea.

As the cool air moves south, it warms and gathers moisture, resulting in rain over the equatorial region, including in Singapore.

Associate Professor Koh Tieh Yong, a climate scientist from the Singapore University of Social Sciences (SUSS), said the cool temperatures last week were due to evaporating rainfall and the formation of rain clouds, which blocked off sunlight.

"Rain falling through the air evaporates at the same time, taking away heat almost continually," he said.

Satellite images showed that wind speeds picked up significantly as temperatures in Singapore fell to 22.8 deg C. The surge continued until Sunday, when temperatures in Jurong West and Admiralty dropped to a low of 21.2 deg C.

Assistant Professor Winston Chow of the National University of Singapore's geography department said low temperatures of between 21 deg C and 22 deg C were not unusual for the less developed parts of Singapore at night during this period.

"But given that the usual daytime maximum temperatures in January are closer to 30 deg C, the persistently low daytime maximum temperatures during the cold spell were extreme," he added.