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

详细摘要

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…

A record-early breakdown of the polar vortex is expected to bring cold weather to the United States by the end of the month.

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.

The polar vortex is a low-pressure band of air centered over the North Pole in the stratosphere, where it typically sits close to the pole and rotates cyclonically around the region.

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.”

The polar vortex is expected to bring chilly temperatures to the U.S. by Thanksgiving week. However, what happens beyond that is still uncertain.

A weak polar vortex in November by no means dictates the rest…

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