SINGAPORE: Rainy and cold weather has been the talk of town lately, following a monsoon surge last Friday (Jan 10) that is set to return this weekend.

Such “sweater weather” is expected to persist over the next few months, with more wet days and more intense rains predicted to hit Singapore.

The nation is currently experiencing northeast monsoon conditions that could get worse during a La Nina event, which may happen as early as this month and last until April, experts told CNA.

The La Nina weather pattern, which brings about wetter and cooler conditions, involves tropical Pacific sea surface temperatures that usually persist for months to about a year.

The world is now on “La Nina watch”, according to the Meteorological Service Singapore’s website.

LA NINA-LIKE CONDITIONS ONGOING

Like the rest of the world, Singapore began 2025 under La Nina-like conditions.

This occurs when trade winds over the Pacific Ocean grow stronger, pushing warm water further west towards Southeast Asia. The water then evaporates and forms clouds that bring heavier rain over the region.

This cycle of warming and cooling of the tropical Pacific Ocean is known as the El Nino Southern Oscillation (ENSO) – a recurring climate pattern.

The warming phase of sea surface temperatures during ENSO is known as El Nino, which brings about hotter and drier weather, while the cooling phase is La Nina. Between these two phases is a third called ENSO-neutral.

Singapore last experienced El Nino from 2023 to 2024, following the last La Nina event that went on between 2020 and early 2023. The two weather phenomena occur alternately every few years.

“We have what looks kind of like La Nina conditions. We are seeing some of the signs of La Nina but it is not a strong one,” noted Mr Tan Wee Leng, senior research scientist at the ASEAN (Association of Southeast Asian Nations) Specialised Meteorological Centre.

“We predict for the next few months – using a lot of different … seasonal climate models – that these La Nina-like conditions will persist for the next couple of months. But it’s predicted to return to neutral in April.”

The World Meteorological Organization also said in its latest update last month that any upcoming La Nina event is likely to be weak and short-lived.

OUTLOOK AFTER JUNE REMAINS UNCLEAR

Conditions are not expected to return to normal up until about June.

As for what the skies will look like after June, Mr Tan said it is “still too early” to forecast what happens to ENSO then.

“Specifically for ENSO, predictions after the northern hemisphere's spring tend to be more uncertain, sometimes termed to be the spring predictability barrier,” he said.

Mr Tan added that current weather models are largely not giving any indication of El Nino or La Nina events in the second half of the year, or whether things will remain neutral. 

The situation will become clearer around May, he said.

“Typically, El Nino events occur every three to seven years. Our last El Nino was in 2023 and 2024, so just purely based on that, we would not expect El Nino (this year) – but there has been precedent. It has happened before,” Mr Tan pointed out.

But some things are a given, like the two monsoon periods that Singapore undergoes every year – the southwest monsoon season starting around May, and the northeast monsoon season which typically runs from December to March.

TOOL BEING DEVELOPED TO EXAMINE IMPACT

To examine the impact of such weather patterns, a National University of Singapore (NUS) research team is working on a tool to identify how vulnerable the Southeast Asia region can be.

This system looks at events like floods, typhoons and heatwaves.

Using natural language processing techniques and artificial intelligence, the team can scan thousands of articles and pick out specific sentences and data that are relevant to events in different regions.

This allows it to establish common themes such as the potential damage to a city or province.

“What we wanted to do with our framework was to actually provide an almost near-real-time tool to extract these impacts and damages,” said Assistant Professor Gianmarco Mengaldo from NUS’ College of Design and Engineering, who is the team's lead.

“For example, if we have a typhoon in Vietnam, we might have Hanoi or other cities very prone to infrastructure damage due to strong winds. After the event strikes, we can actually see what impact the extreme event caused.”

The team plans to launch the tool in the next few months, and is looking to potentially provide it to relevant agencies like the National Environment Agency and the Centre for Climate Research Singapore.