Winter in Canada has been warmer than usual thanks to El Niño, but there’s a chance the weather event could be followed by a chilly La Niña this year, experts say.
While El Niño is characterized by warm, above-average sea-surface temperatures, La Niña is a climate pattern that tends to occur soon after El Niño and brings on opposite, cold effects.
Weather events that cause changes in sea temperatures can have widespread impacts, which is why meteorologists closely monitor them. In the case of La Niña, greater precipitation and winds may lead to rain storms, or even hurricanes.
If La Niña does occur in 2024, meteorologists say it would begin in late summer or early fall.
What is La Niña?
La Niña is a climate phenomenon that results in cooler-than-normal waters appearing off the coast of South America, near Ecuador and Peru.
The weather anomaly occurs when stronger trade winds push warm water away from South America and toward Australia and Indonesia across the equatorial Pacific Ocean, which leaves a buildup (or upwelling) of cold water. That results in cooler air over the west coast of North America, and drier air in the southern United States.
Canada has had strong El Niño weather patterns in the past, which is believed to have factored into warm winters, Global News meteorologist Ross Hull says. While La Niña tends to bring colder winters, Hull says a stronger signal can also lead to bigger storms or hurricanes in Canada.
Will there be a La Niña this year?
Sea temperatures are still warmer than usual and will likely remain that way through the spring, so a La Niña event wouldn’t happen right away, Hull says.
“Towards the latter half of the summer into the early part of fall, July to September, it looks like there’s a good chance we’ll start to transition to a La Niña pattern,” he said.
There is a 58 per cent probability of a La Niña event starting in July to September, according to the Columbia Climate School’s International Research Institute for Climate and Society (IRI) in a report published Jan. 19.
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La Niña also tends to follow a relatively strong El Niño event, which has been occurring since June last year.
There is also a weather period where neither event occurs called El Niño-Southern Oscillation, or ENSO-neutral, where sea level temperatures are close to average. This year, it appears as though El Niño will transition into ENSO during the spring, according to the National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Centre.
“Some state-of the-art dynamical climate models suggest a transition to ENSO-neutral as soon as March-May 2024. The forecast team, however, delays this timing and strongly favors a transition to ENSO-neutral in April-June 2024,” NOAA said in a post published Jan. 11 on its website.
There is a 73 per cent chance that ENSO will occur between April and June, according to the IRI.
How could La Niña impact hurricane and wildfire season?
Many Canadians may have blocked out the memory of last year’s bone-chilling winter, especially in British Columbia, which had abnormally high levels of snow in March. The extreme winter period was due to an extra strong La Niña.
Because it’s predicted that La Niña will likely begin to occur during warmer months of the year, the effects of the cold won’t be known until next winter, Hull says. However, he expects there will be chillier than normal temperatures across the Prairies.
La Niña also tends to create a jet stream where a fast, narrow current of air blows across the globe from west to east. In Canada, the phenomenon will likely lead to more precipitation in the west coast, Ontario and Quebec, Hull says.
La Niña’s chilling effect may be welcomed by western parts of the country that experienced severe wildfires in the summer of 2023. Environment Canada meteorologist Steven Flisfeder told Global News in July that El Niño’s dry conditions did not directly cause the flames. However, climate events can amplify natural patterns in certain regions.
The strength of La Niña’s signal is not yet known, Hull says, but it could factor into the severity of hurricane season.
“Depending on how strong that La Niña signal is, it could have an impact on storm development and how strong those storms are,” he said.
During El Niño, there tends to be more wind shear, which means winds are changing direction and speed over a short period of time. According to Hull, “hurricanes don’t like wind shear.”
“La Niña can provide less wind shear, and thus, the thinking is (there will be) more tropical development,” he says.
Currently, Hull says meteorologists are keeping a closer eye on the remnants of El Niño on wildfire season heading into spring. In B.C., where wildfires burned more than 2.84 million hectares of land last year, the air remained dry throughout the winter.
Moisture from changing jet streams during La Niña may offer some relief to El Niño conditions in B.C., but Hull says it’s still too early to tell what the impact will be.
La Niña’s conditions are also different across the globe and can still be very dry, especially in southeastern parts of the U.S. and along the Pacific coast. California wildfires, for example, can be worse during La Niña.
“That would be something we’d also be looking out for in terms of the more continental picture of how La Niña can impact our weather conditions,” Hull said.
How long does La Niña last?
El Niño and La Niña typically appear every two to seven years.
The last strong El Niño peaked in late 2015-early 2016, and before that in 1997-98, according to NOAA. The last strong La Niña was in 2010-11.
Typically, El Niño and La Niña conditions start to appear around June and last for around nine to 12 months. They peak in December and continue all the way into the following spring.
But what makes recent cycles unusual is that the previous La Niña event persisted for three years in a row, between 2020 and 2023, a pattern not seen since the 1970s.
The recent “triple-dip” La Niña, as described by NOAA, led to numerous natural disasters across the globe, ranging from extreme rainfall and flooding in Australia to droughts in southwestern U.S. and heightened Atlantic hurricane season activity.
Given the duration of the previous La Niña, Hull says it wouldn’t be surprising if this year’s event lasts longer than the standard nine-to-12-month period.
“It’s not yet clear why the La Niña years have been lasting longer, but it is something that researchers and forecasters are looking into,” Hull said.
–with files from Global News’ Kamyar Razavi
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