In Missouri, we usually expect the coldest weather in mid-to-late January, but this year it came in mid February but is expected to end this Friday or Saturday.
Anthony Lupo, an MU professor of atmospheric science, recently explained exactly what a polar vortex is and how it is blocked by the jet stream.
The polar vortex is an area of low pressure that develops over the polar regions. This area of cold air and low pressure is strong from about 6 to 32 miles up and forms in part from a lack of sunlight.
The annual vortex is generally confined to the northerly latitudes, but it can expand and be carried south along with the jet stream. That is what happened this past week, due to a weather pattern called “blocking.” This “blocking pattern” is a ridge in the jet stream that usually shows up about 3.5 miles above the earth and prevents other weather systems from moving in.
That’s how we got this extended period of extremely cold weather; It’s as if the polar vortex is the quarterback and the jet stream is a line of defensive tackles, protecting and preserving the cold weather system.
A polar vortex typically lasts from five to 35 days. Most winter cold spells in Missouri and the Midwest are the result of blocking in the East Pacific and Alaska Sector.
Blocking can actually occur in any season, though it will only get cool or cold relative to that season’s normal temperatures. For example, last spring was cold because of blocking, and blocking also led to some snow in late October 2020.
Dalton Buie of Buie General Services clears the snow off the sidewalk in 0 degree weather on Monday, Feb. 15 in front of New China Chinese Food in the County Market plaza.
An abandoned vehicle on Hwy. 54 near the old Mexico bowling alley sinks deeper during the snowfall on Monday, Feb. 15. Mexico police reporting responding to 13 snow related vehicle incidents including abandoned cars. No injuries were reported.