ENSO, The typical star player of seasonal forecasting is in a funk—the mighty La Niña—is sputtering. While La Niña conditions surfaced this fall, they may fail to meet the duration criteria required for an “official” La Niña designation.
With its grip a little blurry, Canada’s winter hangs in the balance, leaving meteorologists to wonder: who, or what, will quarterback this season’s weather pattern? Some weather players are about to step up in a big way.
A La Niña That’s Not Quite La Niña
Typically, La Niña is a familiar winter script. We know the storyline.
Cold water in the Pacific Ocean orchestrates the jet stream’s movements across Canada. But this year’s La Niña is weak—more like a cool neutral one. To complicate things, the analogue years are fussy and don’t match well. Past transitions from strong El Niño events like last year’s to weak La Niña’s have been rare.
And now, as warmth emerges west of South America, the Pacific Ocean’s story is more muddled. There’s cold water lurking below the surface, suggesting this La Niña could reawaken at a moment’s notice.
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An important factor is the placement of the cold water—east-based versus west-based—will be critical. East-based La Niña’s invite Arctic air to flood much of Canada, while west-based events keep the cold concentrated in B.C. and Alberta. For now, the atmosphere continues behaving like La Niña, even as the event struggles to fully reach the criteria, but the atmosphere doesn’t seem to care about the designation.
Arctic air and the December wildcard
Despite La Niña’s uncertainty, Arctic air is “open for business” in December. If there’s a highlight winter month this season in the east, may we present December?
Last year, an El Niño-driven pattern delivered Canada the warmest winter on record, with many questioning our nation’s frosty reputation.
This year, there’s hope for redemption. December will set the stage, contrasting sharply with last year’s widespread warmth.
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The uncharted waters of a Winter forecast
Without a strong La Niña to rely on, other factors are taking centre stage:
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The Pacific Decadal Oscillation (-PDO): October saw some of the most negative PDO values on record. Historically, such values align with cold Western Canada winters and ridging in the southeastern U.S.
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Heightened solar activity: Canada’s brilliant northern lights this year signal increased solar activity, which can disrupt the polar vortex and heighten the chance of sudden stratospheric warming events.
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Warm Atlantic and Gulf of Mexico waters: This anomaly could influence storm tracks, adding warmth to eastern systems and creating more precipitation variability
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The Quasi-Biennial Oscillation (+QBO): This stratospheric phenomenon impacts the polar vortex and complicates the picture further
These competing forces could lead to a polar vortex that stretches rather than fully disrupts—like play dough pulled apart. When this happened in the winter of 2013-2014, Canada endured huge cold snaps.
SEE ALSO: What is the polar vortex? How it’s responsible for dangerous cold
So as we deal with a sputtering La Niña, this patchwork of influences will dictate where the cold air flows across Canada.
A tale of two winters?
While the west has the highest confidence for below-normal temperatures, the east faces a more dynamic and high-stakes battle. Will fleeting bursts of winter weather dominate the headlines, or can colder air attempt to establish itself? This year’s La Niña—or lack thereof—may not be the driving force behind the winter’s story.
One thing is certain: Canada’s winter isn’t doomed, but its reputation will be hard-fought in the east this year.
Whether it’s the jet stream’s twists and turns or the polar vortex’s stretching acrobatics, one thing is certain, there are likely a few surprises in store for us all. Check back with us, this season is just beginning to write its story.