August M
A vast winter storm is gripping the United States, bringing dangerous snow, ice and plunging temperatures to millions. Forecasters warn the cold will linger, stretching well beyond a typical blast of winter weather.
Behind the disruption lies a powerful atmospheric force that shapes how Arctic cold escapes south.
Storm across states
The BBC reports that more than 160 million Americans are expected to be affected by the current winter storm, with conditions described as life-threatening in some areas. Around two-thirds of the country could experience intense cold, snow or ice, with impacts continuing into February.
Meteorologists say the event has been fuelled by activity in the polar vortex, allowing Arctic air to surge far south into the US.
What is the vortex
According to the BBC, the polar vortex is a band of strong westerly winds that forms high above the Arctic every winter, trapping extremely cold air near the North Pole. When it remains stable, the coldest air stays largely contained.
Problems arise when the system weakens. The winds become more distorted, pushing south and releasing frigid air into mid-latitudes, including the US.
Climate questions
The BBC notes that scientists are still uncertain how climate change may affect the polar vortex in the long term. Amy Butler, an atmospheric scientist at the US National Oceanic and Atmospheric Administration, said there are competing influences.
“There are many things that can change the strength of the polar vortex,” Butler explained, citing sea ice loss, warming in the upper atmosphere and shifting ocean temperatures. As a result, she said climate models “show no agreement” on its future behaviour.
Changing winters
While extreme cold still occurs, the BBC reports that cold snaps in North America have become less frequent and less severe overall. Snowfall has declined in many regions, partly because warmer air causes more winter precipitation to fall as rain.
At the same time, Anderson said a warmer atmosphere can intensify storms when they do form. “There will still be cold and snowy winters in many areas from time to time,” he said, but over decades the broader trend shows continued warming driven by human activity.
Sources: BBC, NOAA, AccuWeather
