La Niña is forecast for winter in Alberta and cold outbreaks may be lurking
It’s getting chillier and chillier in Alberta, and news of a weather phenomenon known as La Niña developing has made an impact on the winter forecast.
Some parts of Alberta have seen some chilly temperatures and snow over the Thanksgiving long weekend, and a developing La Niña may cause some seriously wintry moments over the coming months.
Daily Hive chatted with Alyssa Pederson, a warning preparedness meteorologist with Environment and Climate Change Canada (ECCC), on what Albertans should expect this winter.
Laine Mitchell/Daily Hive
Pederson says earlier this week, the Climate Prediction Centre out of the United States issued an ENSO alert system for a La Niña advisory.
La Niñas are favoured for December to February, which is our meteorological winter; however, using ENSO oscillations is just one piece of the puzzle as to what a season might look like.
Forecasters are currently noting a blob of unusually warm Pacific surface water temperatures off the West Coast, which in turn could cause a compounding effect on how La Niña might impact the climate and the atmosphere.
“It’s a little bit more complex than just La Niña,” Pederson stated.
What does a La Niña influence?
When we see La Niñas over the winter, it means we’re going to be getting ridges of high pressure over B.C. and over the western Pacific, and Pederson added that with that warmer water currently sitting in the Pacific, it may actually intensify that to make it stronger.
“Then what that means is we get like a northwest wind or a flow pattern through the Prairies, which means we would generally be a little bit cooler and a little bit wetter than normal for, you know, the Rocky Mountains east through Alberta, cooler and wetter than normal is what it’s normally supposed to bring.”
If you’re an avid skier or snowboarder, that’s welcome news for ski hills scattered across the Alberta Rockies.
How often do La Niñas occur in Alberta?
Looking back at previous winters, Alberta has seen numerous La Niña winters this decade alone, including the winters of 2020/21, 2021/22, and 2022/23; however, just one had a noticeable impact of being wetter and cooler than normal.
Pederson noted that things to consider are the cooler-than-normal and wetter-than-normal conditions when looking at La Niñas’ all-time events, and what we’re seeing now with climate change is that La Niñas of today are having similar temperature profiles and precipitation profiles that El Niños did 30 years ago, thanks to climate change.
“We’re actually starting to see La Niñas be drier than they have in the past and warmer than they have in the past, which is kind of where that El Niño of the past. Everything has shifted a little bit.”
Can a polar vortex still occur during a La Niña winter?
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If you thought the impact of a La Niña event would eliminate the risk of brisk cool air reaching down from the Arctic and hugging Alberta at times this winter, think again.
When it comes to the polar vortex, Pederson said, as it breaks down, that’s when the wind speeds are a little bit weaker, and therefore you get these big lobes of cold air coming down from the Arctic. If the jet stream is stronger, it tends to hold the polar vortex in and around the Arctic.
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What La Niña does, what climate change does, and what some of these other things — like that warm blob in the Pacific oceanographers have spotted — can do, is change the temperature structure of the atmosphere, which then is what can potentially weaken the jet stream that holds the polar vortex in the north.
“When that jet stream then gets weakened, that’s when we actually see these big events, these cold events, happening down in our area. So they’re absolutely related. And yeah, I would expect it, looking at a bigger picture of colder than normal and wetter than normal that, yeah, maybe that indicates that we’re looking at more instability in that jet stream, and therefore more outbreaks of that cold, cold air,” Pederson added.
It is harder to hang your hat on many of the outcomes of this winter, due to the La Niña forecast to be a relatively weak one, while other things, like the general warming of the planet or that blob of warmer Pacific water, might have enough of a change to negate the change, potentially, of the La Niña.
At the end of the day, Pederson said no matter what situation we’re in, whether it’s a La Niña or an El Niño event, we do get winters here, and thanks to the effects of climate change, we’re seeing bigger swings in the weather.
“We could have way above normal warm, people think global warming when they think 10 degrees in January, kind of events. But then we have opposite swings well into those extreme, extreme colds,” Pederson said.
“Where we are in Alberta, we’re still very, very prone to all of that. I’d be prepared in Alberta for the gamut of all of it every winter.”