It seems that meteorologists have spotted something curious when it comes to winter patterns this year. According to researchers from NOAA, parts of the atmosphere are behaving in ways they haven’t seen in quite a while. From La Niña’s lingering presence to a notable wind flip in the stratosphere, even an early occurrence of the Arctic’s polar vortex is making waves!
Specifically, when we say “pattern,” meteorologists are referencing how the various layers of our atmosphere interact. Experts like Dr. Amy Butler from NOAA’s Chemical Sciences Laboratory and Dr. Daniela Domeisen from ETH Zurich explain that slow underlying conditions can really shake up winters in the U.S. This season could unfold in ways we wouldn’t typically expect if early forecasts ring true.
First off, La Niña is at play, causing the Pacific waters to cool down. NOAA reported lower-than-average sea-surface temperatures during both September and October. Generally, when La Niña prevails, it’s associated with a stronger polar vortex that sways the jet stream. On the other hand, during El Niño, the vortex usually takes a much weaker stance. What we are seeing in this year’s situation is quite different!
So, what exactly is this polar vortex everyone is talking about? In simple terms, it’s a band of powerful winds circling the Arctic stratosphere (which is the second-lowest layer of our atmosphere). Climatologist Dr. Judah Cohen describes the polar vortex as a sort of atmospheric barrier that keeps cold air contained. What’s got experts worried this year is how conditions might be influencing its behavior—especially due to big warm air bursts in the stratosphere, called sudden stratospheric warming (SSW) events, that can actually disrupt or even flip it. When these bursts strike, temperatures in the polar stratosphere might shoot up by nearly 86 to 122°F in a matter of days!
Now, though the instability of the vortex is certainly a cause for some concern, the timing of this instability is even more alarming. NOAA’s predictive models had spotted warming trends as early as the late fall—way ahead of the winter season, which is quite out of the ordinary! The last times we saw these kinds of early seasonal disruptions were back in 1958, 1968, and 2000. Typically, we witness peak SSW events from January through March, so we could be bracing for significant changes between mid-December and mid-January.
And wait, there’s more! The Quasi-Biennial Oscillation, or QBO, is another important pattern that usually takes place over the equator roughly every 28 months. It tends to flip stratospheric winds and, for the winter season of 2025-26, it’s shifting to its easterly phase. According to researchers Hiroaki Naoe & Kiyotaka Shibata, these easterly QBO winters are notorious for frequently weakening the polar vortex compared to those from the westerly phase.
To put this into perspective, while La Niña might be nudging for a stronger polar vortex, the easterly QBO seems to pull the other way! We’ve really got some mixed signals coming in from our atmosphere right now.
What could all these developments lead to? Predicting the weather has never been an easy task. Major SSW occurrences often lead to shifts in the jet stream and potentially increased cold air events across North America and Europe in the weeks to come. In fact, some of you might recall the 2018 Stratospheric Warming event known as the “Beast from the East” which had significant impacts in Europe or the severe cold front that hit parts of central and eastern U.S. early in 2021.
When the stratosphere undergoes big changes, North America’s weather can swing between random warm spells and sudden cooldowns. This flickers the jet stream, drawing colder Arctic air southward, which typically plummets temperatures and brings snowfall. Consequently, regions basking in mild winter weather might find themselves facing chilly days after a warming event occurs.
If these stratospheric changes keep rolling in, it wouldn’t be far-fetched to predict multiple snowstorms affecting parts of the U.S. and Europe. An unsteady vortex coupled with a wavering jet stream might also set the stage for enduring stormy conditions with irregular wet weather, potentially dusting regions not prone to heavy winter snow with a surprise Arctic chill.
That said, not every area will experience these weather patterns all at once. So don’t throw out your winter coats just yet as there’s still a lot uncertain!
Currently, NOAA’s outlook for the 2025/26 winter still shows the usual impacts of the La Niña pattern, expecting a wetter Pacific Northwest, a drier South, and warmer Southeast. Still, there are loud alarms about how stratospheric shifts could flip these long-held expectations upside-down. The concurrent presence of La Niña paired with an easterly QBO and an early vortex disruption is a rare confluence to note. We’ll have to wait and see what surprises lie ahead!
