A year later: A look at what caused February 2021′s Arctic blast, waves of wintry weather
WACO, Texas (KWTX) - The unprecedented winter storms in mid-February 2021 is still fresh in the minds of many Texans.
Wave after wave of wintry weather with near all-time record cold temperatures created chaos in the Lone Star State as roads froze over for days, businesses and homes flooded from bursting pipes, and as the power grid collapsed leaving hundreds of thousands in the dark with no access to heat.
Texas is no stranger to cold temperatures and bouts of wintry weather, but the elements came together to create a week of weather unlike any other seen in the state.
Plunging polar jet stream sent the polar vortex stateside
The Waco Regional Airport, where weather records are recorded in Central Texas, shattered the record for most consecutive hours at or below freezing. The 205 hours of sub-freezing temperatures from February 10th to February 19th was really only possible because of one atmospheric phenomenon: the polar vortex.
Despite the scary sounding name, the polar vortex is actually present year round. During the summer months and during most of the winter, the polar vortex remains bottled at the North Pole by the polar jet stream. Ironically, a strong polar vortex isn’t an issue for North America. Whenever the polar vortex weakens, polar air is more “wobbly” and can send the polar jet stream south.
In February 2021, the polar vortex was centered in South-Central Canada but the polar jet stream was almost directly overhead.
Unlike with the round of wintry weather in February 2022, when the jet stream dropped deep into the Southern Plains and quickly moved out, the jet stream in February 2021 was locked into place for multiple days.
Embedded within what’s called a longwave trough (which is just a fancy term for an expansive drop in the jet stream) was lobes of vorticity (or spin). The spin in the atmosphere tapped into moisture and produced freezing rain and snow.
Not one, not two, but three rounds of wintry weather in just seven days
Texas and winter weather just flat out don’t mix, but the four rounds of wintry weather across the state meant conditions went from bad to worse every few days.
In Central Texas, we were spared the fourth round of wintry weather which primarily impacted South-Central Texas, but waves one, two, and three, took aim at our neck of the woods.
The first wave of precipitation came on February 11th in the form of freezing rain. Upwards of a half-inch of liquid precipitation fell and froze to many roadways. Since temperatures did not warm up above freezing at all, we couldn’t thaw out and improve road conditions.
With ice still on the roads, the most impactful wave of weather was Valentine’s Day afternoon into the morning of February 15th. Widespread snow, with accumulations between 2″ and 6″, meant any roads that may have been passable quickly weren’t. With ice and snow on the ground and cloudy skies overhead, the snowpack and an open door to the Arctic kept temperatures at least 10° below freezing for nearly 48° hours.
The final wave of wintry weather was icy as a tongue of warm air aloft just barely above freezing melted what would be another round of snow into freezing rain on February 17th. The ground was a snow-reo with a layer of snow stuck between two layers of ice. The light at the end of the tunnel came as skies cleared. The partial melting that came from temperatures above freezing during the afternoon of February 19th turned into a rapid melting on February 20th. Icy patches lingered through the 22nd, but conditions greatly improved nine days after the first round of wintry weather arrived.
While wave after wave of wintry weather didn’t help any to keep the lights on in Texas, the primary cause of the power grid failure was just how deep the cold air sunk into the state. Outside of some cities along the immediate Gulf Coast and towns in far West Texas, nearly the entire state felt sub-freezing temperatures on February 15th, 2021.
A myriad of records not only broken but completely obliterated
The headline record from February’s winter storm was the 205 consecutive hours below freezing, a full 55 hours longer than the previous record cold-streak.
Records for the coldest high temperature were set on February 11th and then each day from the 14th to the 18th.
The daytime cold didn’t translate to as many low temperature records. We set only two low temperature records including what was the third lowest temperature of all time at -1°.
February 2021 was the third snowiest on record with 4.6″ falling at the Waco Airport. A daily snowfall record of 2.5″ was also set on February 15th.
Despite the record book revisions, February 2022 was NOT the coldest February on record. The average temperature of 43.5° was the 5th lowest all-time. The average high temperature managed to only be the 7th lowest at 54.3° thanks to a myriad of 70s early and late in the month. The average low temperature was almost 3° warmer than the 29.9° lowest average low set in both February 1936 and February 1905. February 2021 finished with an average low temperature of 32.7°
Copyright 2022 KWTX. All rights reserved.