The Arctic polar vortex ground to a halt and reversed direction on Nov. 10, with an early-November wind reversal that has never occurred when the system is typically strengthening.
Current polar vortex wind speeds dropped to -0.1 m/s, matching walking speed, roughly 30 km above the Arctic. History implies that strong El Niño events usually strengthen the polar vortex, making this sudden reversal entirely unexpected.
When major disruptions occur high above the Arctic, the influence can work downward through the atmosphere. This process shifts the jet stream, enhances blocking patterns, and allows Arctic air to surge farther south.
Historic wind reversal timeline
The stratospheric disruption follows a specific timeline tracked across November. The historic disruption (reversal) occurred from Nov. 10 to Nov. 13.
Forecast models show the vortex recovery between Nov. 14 and Nov. 20. Forecasters will then watch the Pacific Ocean from Nov. 20 to Nov. 27 to see if ridging returns to the northeast Pacific and Alaska.
European ensemble guidance highlights a potential transition of the eastern Pacific oscillation into negative territory. This shift could help reshape the storm track that has been ravaging the coast of British Columbia.
Mild temperatures across Canada lack Arctic air reservoirs
While the polar vortex experiences high-altitude disruption, record-breaking El Niño conditions and an energized Pacific jet stream are delivering widespread, above-seasonal temperatures across the heart of Canada. A blowtorch pattern across Northern Canada extends exceptionally mild temperatures deep into the Arctic.
If the upper-level pattern becomes favorable for delivering cold air south, there is no deep reservoir of Arctic air. The coldest air currently resides on the other side of the pole in Siberia, meaning any outbreak would take longer to reach North America.
Although the reversal is unprecedented, it will be short-lived. Forecast models indicate stratospheric winds will rapidly increase back to normal by the third week of November, eventually reaching over 25 m/s.
Frequently asked questions about winter weather
Can a short polar vortex reversal affect weather for weeks?
Yes, the duration alone does not determine possible surface impacts. The development of blocking patterns and regional weather conditions all matter, as well.
Does this event invalidate existing winter forecasts?
No, a powerful El Niño remains the dominant driver of the forecast and an important influence. Seasonal forecasts describe the broad pattern, not every cold snap or winter storm, and the polar vortex disruption just added another layer of complexity to the forecast.
Could Canada still experience an Arctic outbreak in December?
Atmospheric roadblocks and a compromised polar vortex can heighten the chances of frigid air spilling southward. Even so, the destination of this cold air remains highly uncertain, while prevailing El Niño conditions point toward a generally mild setup overall.
Why did the polar vortex weaken so early?
The polar vortex was disrupted by forceful atmospheric waves moving upward from the lower atmosphere, which decelerated its primary westerly currents and provoked rapid stratospheric warming. Although the historic El Niño may have played a part by boosting wave activity toward the stratosphere, its actual contribution to this particular occurrence remains highly ambiguous.
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