The ‘triple-dip’ La Niña is finally over.
Nearly three years of abnormally cool waters in the eastern Pacific Ocean boosted several rollicking hurricane seasons and set off a flurry of extreme weather across North America.
Now that it’s over, though, what will it mean for your weather here in Canada? It depends on where you live—and what happens later this summer.
La Niña is out, but an El Niño might not be far behind
The U.S. Climate Prediction Center (CPC), a branch of NOAA, announced on Thursday the end of La Niña, marking a return to near-seasonal water temperatures in a critical portion of the eastern Pacific Ocean.
La Niña is a monthslong pattern of cooler-than-normal surface water in the equatorial Pacific off the western coast of South America. La Niña, along with its warmer counterpart El Niño, can have a profound impact on weather patterns around the world.
This was our third consecutive winter with La Niña conditions present, a rare ‘triple-dip’ that likely enhanced cooler and wetter weather in Western Canada during the fall and winter months. These conditions have been around almost persistently since the summer of 2020, which provided a boost to the very active 2020 and 2021 Atlantic hurricane seasons.
Now that La Niña is over, NOAA’s forecasters predict seasonable water temperatures in this crucial part of the eastern Pacific heading into the early summer months, with a possible shift to El Niño—abnormally warm surface waters—by the peak of hurricane season.
WATCH: What a rare ‘triple-dip’ La Niña means in a warming world
Thousands of kilometres away, but still a Canadian affair
How does the water temperature thousands of kilometres away affect Canadian weather?
It’s tough to imagine that as little as one-half of one degree of warming or cooling in a faraway part of the ocean can have such a large impact on your weather here at home. But it’s a perfect example of how our global atmosphere is an interconnected system that can respond to changes thousands of kilometres away.
The cooler waters of a La Niña in the eastern Pacific can drag the jet stream farther south during the colder months, allowing repeated spells of wet, snowy, and cool weather to wash over Western Canada. La Niña winters also tend to see milder conditions across the eastern half of the country.
What these shifting patterns could mean for your summer to come
The teeter-totter between warmer and cooler ocean waters is driven by variations in air pressure and prevailing winds between South America and Australia. This overall cycle is known as the El Niño-Southern Oscillation (ENSO).
Prevailing winds over the Pacific that typically blow from west to east will sometimes slow down and reverse direction, pushing warmer water toward Australia. This reversal forces cold water deep in the ocean to rise to the surface near South America, leading to a La Niña.
If these westerlies grow stronger, on the other hand, it can blow warm water east and pile it up off the South American coast, leading to an El Niño.
When conditions are normal and water temperatures are around average for the season, we enter a “neutral” period where the region’s water temperatures don’t have an overall effect on global weather. This is the pattern that NOAA’s forecasters predict for the coming months.
A potential shift to El Niño during the latter half of this summer could have some effects on Canadian weather.
The warm waters of an El Niño can increase stormy weather over the eastern Pacific, which leads to enhanced wind shear blowing into the Atlantic basin.
Wind shear can limit the development of tropical disturbances, potentially leading to a below-average hurricane season. An El Niño can also lead to milder winters in the western half of Canada.
WATCH: How La Niña and El Niño affect global weather patterns
Thumbnail image courtesy of Unsplash.