Strong El Nino delays Singapore’s dry season relief to late October

El Nino’s influence on rainfall and temperature

El Nino events tend to reduce cloud cover from October to November, bringing less rainfall and increasing surface temperatures over that period, said Koh Tieh Yong, a meteorologist from the World Climate Research Programme’s Working Group on Asia-Australia Monsoon.

The three strongest El Nino events since 1980 happened in 1982/1983, 1997/1998 and 2015/2016.

The impacts of a single El Nino event tend to spill over two years.

MSS data showed that El Nino events can affect rainfall and temperature during the October-to-November period.

For instance, the long-term average rainfall from 1991 to 2020 for those months was 490.7mm of rain.

This figure drops during strong El Nino events. The average rainfall for those two months was 450.5mm in 1982, 275.3mm in 1997 and 351mm in 2015.

Similarly, the long-term average temperature for those two months was 27.6 deg C. In 1982, the average temperature for those months was 26.8 deg C; in 1997, it was 28 deg C; and in 2015, 28.3 deg C.

“More recent El Nino events also tend to be warmer than those occurring more than 30 years ago due to global warming,” said the MSS spokesperson. “1982’s temperatures were mostly below this average, illustrating the effect of the long-term warming trend.”

She added that El Nino tends to have a stronger influence on rainfall and temperature around the February to March period.

For instance, the long-term average rainfall for those two months is 345.9mm. This dropped to 64.1mm in 1983, 138.9mm in 1998 and 263.5mm in 2016.

In terms of temperature, the long-term average for February and March is 27.6 deg C. During the 1983 El Nino year, the average temperature for the period was 27.8 deg C. In 1998, it was 29.2 deg C, and 28.4 deg C in 2016.

Fire-dousing rains

True relief from haze could only come later in the year, when monsoon rains reach Indonesia in late December or early January, said Koh, who is also an adjunct associate professor at the National University of Singapore.

These rainfall events are expected to greatly help to contain and put out the haze-inducing fires, he said.

However, NIE’s Wang warned that under a strong El Nino, the respite could be weaker and shorter than normal.

“El Nino suppresses cold surges and rainfall, and the monsoon’s own dry phase from late January to March returns quickly,” said Wang.

The north-east monsoon season brings rainier weather over Singapore between November and January, but then has a drier period from February to March.

Said Wang: “So expect a brief improvement around December, followed by a return to warmer, drier and potentially hazy conditions in the latter half of the monsoon.”