THE LETHAL ATMOSPHERIC SETUP BEHIND A DEADLY ARCTIC OUTBREAK ~ The Washington Post

How ingredients came together for an onslaught of bone-chilling temperatures and a barrage of storms

A National Weather Service map of alerts for Sunday. Note that some areas were under more than one of these alerts at one time or another. Winter alerts are identified in the key. (NOAA/NWS)
A National Weather Service map of alerts for Sunday. Note that some areas were under more than one of these alerts at one time or another. Winter alerts are identified in the key. (NOAA/NWS) 

By Tom NiziolFeb. 16, 2021 at 2:26 p.m. MSTAdd to list

It took a while, but when winter decided to kick into full gear across the heartland of the nation these past few days, it did so with a passion.

Almost the entire Southern Plains was under winter storm warnings on Valentine’s Day, the alerts encompassing some 90 million people. Only nine states within the Lower 48 were not under some sort of winter alert Sunday, with wild winter conditions spanning the continent.

Live updates: Power outages plague Texas, other states amid deadly cold, snow

In addition to heavy snow and ice, wicked wind chills covered the nation’s midsection. Even such places as Seattle and Portland, Ore., didn’t escape unscathed; Arctic air spilled through mountain gaps in the northern Rockies, sneaking its way to the Pacific Coast while producing damaging snow and ice.

So what’s behind the onslaught of bone-chilling temperatures and the barrage of storms? It has to do with a number of overlapping factors that came together in the wrong place at the wrong time.

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(Tim Meko/The Washington Post)

Generally speaking, most weather catastrophes share similar DNA. They all are made up of smaller meteorological ingredients. Individually, any one of these features alone may not be problematic, but added together, it’s the perfect recipe for a high-impact disaster. As the adage goes, the sum is greater than the parts.

Looking back, it’s clear this extreme weather pattern had been incubating for a while. It began in early January with a perturbation of the polar vortex. That disruption knocked the whirling eddy of bitter cold air and low pressure off-kilter, resulting in upper-atmospheric warming that displaced cold air to the mid-latitudes.

A look at the upper-air pattern between Feb. 11 and Feb. 16. Note the high pressure (red) across the Polar Region, which allowed the Jet Stream to dip far south across the United States. (Tropical Tidbits)
A look at the upper-air pattern between Feb. 11 and Feb. 16. Note the high pressure (red) across the Polar Region, which allowed the Jet Stream to dip far south across the United States. (Tropical Tidbits) 

According to Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research, that sudden stratospheric warming was integral in helping us get to where we are now.

~~~ CONTINUE ~~~

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