Looking back at this past winter, for many people it likely seemed like it was colder and snowier than normal. While cold temperatures and snow are not at all unexpected in many parts of the world, they are quite rare in others. In addition, the severity of winter weather can change drastically from one year to the next, which makes understanding it difficult for many.

One interesting phenomenon that causes especially cold and snowy winters is known as the polar vortex.

A polar vortex is an area of low-pressure that swirls at the Earth’s poles. They exist over both poles, but for most readers, the one over the North pole will have a much greater effect on them. In this region, the wind of the polar vortex travels counterclockwise, and ranges from 16-50 kilometers (10-30 miles) above the surface.

When this vortex breaks down, it causes a polar jet stream to push down to lower latitudes, dipping well into North America, Europe, and Asia. While this can happen any time of the year, it is much more noticeable during the winter months because it can cause the temperatures to drop down to uncommonly cold levels.

The National Oceanic and Atmospheric Administration (NOAA) is working on their ability to predict these events.

It was explained that these cold events are actually caused by a sudden warming up in the stratosphere, which disrupts the normal path of the polar vortex. They recently said on the NOAA website:

“there are certain ingredients that need to come together to drive a sudden stratospheric warming. These can be boiled down to two main factors:

1. persistent weather patterns in the lower atmosphere (troposphere) that can amplify large-scale atmospheric waves vertically into the stratosphere; and
2. ideal wind conditions in the stratosphere that steer the arriving waves and encourage them to break near the polar vortex, which rapidly slows the polar stratospheric winds.”

When this happens, the freezing air can be ejected from the polar region and push south to parts of the world that normally don’t get these temperatures.

It is still difficult to accurately predict this type of event. NOAA said that there was about a 55% chance that the polar vortex would remain stable during the 2024-2025 season, but that was certainly not the case.

Additional study of these events will hopefully improve the ability to know exactly when they will come so people can be better prepared.

If you thought that was interesting, you might like to read about the mysterious “pyramids” discovered in Antarctica. What are they?