It was…temperatures high in the stratosphere above Siberia. In the first week of January, they increased from about minus 92 degrees Fahrenheit to 8 degrees Fahrenheit. While these “sudden stratospheric warming” events happen to some extent every year, this one is categorized as a major event and is less common.
The mass of extremely warm air threw the freezing polar vortex out of balance, shoving it off its North Pole axis so forcefully that it in effect split in two, as if growing a pair of legs: one over North America and one over Europe…
The interaction between disruption to the stratosphere and weather in the troposphere is still not precisely understood. But when the vortex in the stratosphere is disrupted—split, displaced, or elongated—it can push the jet stream below it south, bringing Arctic air into cities in the U.S., Europe, and Asia.
What this article was predicting over a week ago has landed in our lap. And many others in the Northern Hemisphere. Read the article for the complex and predictable parts of the process that dropped Arctic temperatures in lands further south.