2021 was Singapore’s second wettest year since 1980, with 33% more rain than average: Met Service

SINGAPORE — Singaporeans who thought 2021 was unusually wet weren’t wrong. It was the country’s second wettest year since 1980, with total annual rainfall at Changi Climate Station 33 percent above the long-term average.

And in January, the rainfall was the highest in more than 100 years.

But while the wetter conditions led to several notable weather events, such as an unusually wet August, the Meteorological Service of Singapore (MSS) said they were also helping to moderate the island’s overall temperature.

MSS published the results on Friday January 28 in its annual weather review, which also recorded the period from 2012 to 2021 as Singapore’s hottest decade.

ABOVE-AVERAGE PRECIPITATION

Most months of last year saw above average rainfall.

This led to an annual record total rainfall of 2,809.6mm at the Changi climate station, 33% higher than its long-term average of 2,113.3mm.

Averaged across Singapore’s 32 climate stations, the annual total rainfall was 3,167.7mm, 25% higher than the long-term annual average of 2,534.4mm.

Based on the island-wide average, MSS said almost all of these wettest months ranked among the top 10 wettest months for the respective months over the past four decades.

Singapore had its wettest year in 2007. The total annual rainfall recorded that year at Changi Climate Station was 2,886.2 mm.

MSS previously told TODAY that it operates a dense network of stations as there could be variations in rainfall across the island depending on each event. As such, it can be difficult to represent average rainfall based on a single station.

Although there is variability in precipitation across the island, the trend in annual precipitation from year to year at all stations on the island is generally similar.

“Changi Climate Station, with its continuous long-term records, thus provides a good indication of rainfall trends in Singapore,” the meteorological service said.

WHAT CAUSED IT?

Explaining why 2021 was exceptionally wet, MSS said it had to do with last year’s La Nina conditions and the presence of a negative Indian Ocean Dipole. Both are meteorological phenomena.

La Nina conditions and negative dipole events from the Indian Ocean usually bring wetter than average conditions over Singapore and the neighboring region, especially during the southwest monsoon season.

La Nina conditions prevailed in the first quarter of 2021, before returning to its neutral El Niño conditions in the second quarter of last year.

About four months later, these La Nina conditions reappeared toward the end of the third trimester.

During this quarter, MSS said an Indian Ocean Negative Dipole – a natural climate phenomenon influencing rainfall patterns around the Indian Ocean – was also established.

His strength fluctuated considerably in the second half and returned to neutral at the end of 2021.

THE HOTTEST DECADE

Along with significantly above average rainfall, MSS said the past 10 years from 2012 to 2021 were the warmest decade on record, with an average temperature of 27.97C.

This is 0.02°C warmer than the previous high of 27.95°C from 2010 to 2019.

The annual average temperature for 2021 was 27.9°C, 0.1°C above the long-term average of 27.8°C.

“This ranks 2021 as the 10th hottest year on record for Singapore, along with 2018, 2014, 2009 and 2004,” MSS said.

In the first half of 2021, near-average temperatures were observed for the most part, while warmer than average conditions were observed in the second half.

These warmer than average temperatures towards the end of the year, MSS said, were associated with relatively drier weather conditions.

December 2021’s average temperature of 27.7C was a joint record with December 2015 for the hottest December since temperature records began in 1929.

In contrast, MSS said the cooler than average temperatures recorded in January and August 2021 were associated with significantly above average rainfall in those two months.

The average temperature was 26°C in January 2021 and 27.6°C in August 2021, 0.8°C and 0.5°C lower than their respective long-term monthly averages.

MSS also declared January 2021 to be the coolest January in 30 years, while August 2021 was the second coolest August in two decades.

NOTABLE WEATHER EVENTS

MSS also highlighted three months – January, February and August 2021 – which saw the occurrence of what it described as notable weather events.

He said “unusually wet and cool weather” was recorded in January 2021 due to a northeast monsoon surge which brought continuous widespread rains to Singapore on the first weekend of the year.

The highest daily total rainfall of 210.6 mm was recorded at Changi Climate Station on January 2, 2021.

A week later, another monsoon wave brought windy and rainy weather between January 8 and January 13, 2021. The rain was heaviest on January 10, 2021.

MSS said monthly rainfall recorded at Changi Climate Station for January 2021 was 692.8mm, with over 90% (648.4mm) recorded in the first fortnight alone.

This means that January 2021 was the second wettest January since rainfall records began in 1869, as it surpassed the second highest value of 634.5mm recorded in 1918.

In contrast, February 2021 turned out to be “very dry and windy”. The highest daily rainfall total was just 46.9mm in Jurong West on Feb. 11, while Changi Climate Station recorded just 1mm for the entire month.

February 2021 was the second driest after February 2014, which recorded only 0.2 mm of precipitation.

February 2021 was also the second windiest since continuous wind records began in 1984. Changi Climate Station recorded an average daily wind speed of 13.1 km/h, just behind the 13.7 km/h h recorded in February 2014.

While August is usually one of the driest months of the year, MSS said there was “well above average” rainfall across the island in August 2021, the Changi climate station recording nearly double its long-term monthly average.

There were two days with unusually heavy rains that triggered flash flooding in some areas.

Multiple bouts of moderate to heavy thundershowers in the pre-dawn and morning hours resulted in flash flooding in areas such as the junction of Tampines Avenue 10 and Pasir Ris Drive 12 on August 20, 2021 and Bukit Timah on August 24 2021.

MSS said August 24, 2021 was the wettest day of last year. A “remarkable daily total precipitation” of 247.2 mm was recorded at Mandai station, setting a record for the highest daily total precipitation for the month of August.

He added that this far exceeded the previous record of 181.8mm at Changi on August 22, 1983.

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