How did it get so cold in Texas?

Over the last 10 days, frigid temperatures and snow have devastated Texas and other Southern states.

Lows of -19°F. were recorded in northern Texas. The Dallas Fort Worth airport experienced the coldest three-day stretch ever on record February 14 through 16 with an average temperature of 10.8°F., according to the National Weather Service. It has snowed in all but eight of the state’s 254 counties, shows a map from the Midwestern Regional Climate Center.

Melody Speer farms and ranches with her family near Uvalde, Texas. As of Thursday morning, her area had received about 10 inches of snow over several days. Her family spent a day without electricity and about three without their main water supply. She’s thankful they were able to switch over to a well, and is concerned about fellow Texans who are going on a week without electricity and don’t have that type of flexibility.

It’s been more than 35 years since Speer remembers weather like this. "In 1985, we had 13 inches, but it snowed, and we were back to normal in no time. We didn’t have issues with power and water. The length of this storm is unprecedented," she explains.

Map of Texas cold temps
Photo credit: Iowa Environmental Mesonet

What is a wobbly polar vortex?

These unusual winter conditions persisted in the Lone Star State because of a wobbly polar vortex, explains Iowa’s state climatologist Justin Glisan. Polar vortex is a term that’s been popularized in recent years and is often used to describe streams of escaping arctic air. Really, the polar vortex is always there, he says.

“The polar vortex is actually a low-pressure center over the Arctic basin, sitting right on top of the North Pole. It acts as a dam for all the arctic air, keeping it where it should be, in the high latitudes,” he explains.

Normally, the polar vortex is circular in shape and encompasses much of the arctic. However, in January, longer-term climate models started to show that the polar vortex was beginning to wobble. Jet streams that normally keep warmer air out of the arctic also become unstable.

Polar vortex explained
Photo credit: NOAA

This phenomenon made the polar vortex take on a shape similar to a starfish. “If you were looking straight down on the globe, you would have bulges of cold air farther into the mid-latitudes, and then ridges in the jet stream where warm air is pushed farther poleward,” says Glisan.

Destabilization of the polar vortex began in late January when Europe was going through a cold snap. This caused the polar vortex to become “wobblier” and pushed a bulge of frigid arctic air down through the Midwest. The freezing temps lingered, thanks to high pressure systems moving warm air farther north on either side of the bulge of cold air.

“This was happening over the Atlantic basin and the Pacific basin, so it squeezed that bulge farther south, and held that pattern. We call it atmopsheric blocking. We had nine to 10 days of extremely cold temperatures. The squeezing motion was able to produce a higher amplitude bulge, and that’s where we get the devastating weather events down in Texas,” Glisan explains.

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