What An Early Polar Vortex Combined With El Niño Means For Winter Weather

The expected wobble in the polar vortex that sends Arctic temperatures south, however, could be in competition with the strong El Niño forecast for this winter—but experts say that how it will impact our weather remains to be seen.

Every few winters, the polar vortex will be disrupted, causing what is known as sudden stratospheric warming, in which temperatures in the stratosphere jump by 50-70 degrees in a few days. That can displace cold air, pushing it down towards parts of North America, Europe, or Asia.

A wobbly polar vortex can shape weather in the northern hemisphere—though it typically takes a few weeks for its impact to be felt. The breakdown causes cold air that is usually trapped to spill out of the Arctic toward lower latitudes, triggering a cold snap. “If the polar vortex gets disrupted and weakens, then that cold air tends tends to be released southward into the mid-latitudes, and of course, with more cold air, you can also have an increased chance or risk of snowstorms or ice storms,” says Judah Cohen, a climate scientist at MIT.

The polar vortex disruption currently being observed by meteorologists is the earliest ever recorded, as it typically weakens during the second half of winter. “Typically we think of this happening toward the end of the winter, in January or February,” says Andrew Charlton-Perez, professor of meteorology at the University of Reading. “So what's unusual about this event is that it's the earliest recorded sudden warming event.”

A weak polar vortex in November by no means dictates the rest of the winter. “This is not going to determine how our winter is going to be,” says Cohen. “It could make it colder right at the start of winter, but I don't think its influence will last much longer than that.”

Experts say that it’s too early to say how the so-called “super El Niño” might interact with the polar vortex. “Because these events are so rare, we have perhaps 45 or so of these events that we've ever observed,” says Charlton-Perez.

There’s a chance El Niño and the polar vortex work together, which would mean this winter would have mild weather in store. “If the pole vortex is in a strong circular state [for the rest of winter], then it's going to influence our weather to be mild, and the El Niño influences our weather to be mild, so they're reinforcing each other,” says Cohen.