What explains the series of violent tornadoes in the United States

Under the rubble, an employee made a desperate plea for help on Facebook. In the audio, you can hear some of your colleagues screaming and crying in the background.

“We are under arrest, please get help,” Kiana Parsons-Perez – who was later rescued – said in the recording broadcast by CNN.

The BBC’s Nomiya Iqbal, who visited Mayfield the morning after the disaster, reported seeing “collapsed houses”, “buried under piles of their wreckage – toys and shoes strewn among twisted metal parts and torn trees”.

“It’s like you walked into a disaster filming set. It’s a ghost town.”

The National Weather Service received more than 30 tornado notifications in six states on Friday. The most destructive of them cut an impressive 365 kilometers, across four states: Arkansas, Missouri, Tennessee, and Kentucky.

The Midwest and Southeast of the United States have some ideal conditions for hurricane formation.

In this area, dubbed “Hurricane Alley” (literally “Hurricane Alley”), the cold, dry air that comes from southern Canada tends to collide with warm, moist air moving north from Canada, and the Gulf of Mexico. This encounter creates atmospheric instability that can in turn form the violent air columns that characterize hurricanes.

Most of the tornadoes seen in this region occur in May and June – another factor that caught our attention on Friday’s episode, as it is uncommon for these extreme events to occur in December, during the winter.

One element noted among the possible causes of the formation of so many violent tornadoes, however, is the unusually hot temperature observed in part of the country the day before, well above December averages in some areas.

According to the Washington Post, a powerful low-pressure system that emerged from the Great Plains, in the north, was intensifying when a polar jet stream fell in the central region of the country and crossed the mass of hot air in its path. It caused a record heat wave in the region that includes the states of Tennessee, Arkansas, Mississippi, Texas and Louisiana.

In Memphis, Tennessee, according to the US Meteorological Service, thermometers registered about 26 °C (79 °F), nearly 15 °C (26 °F) more than the average for that period.

“He didn’t know it was December – temperatures in the 70s and 80s,” Mississippi meteorologist Craig Sissi wrote on his Twitter page.

However, climate scientists stressed that more studies will be needed to better understand what happened Friday night.

Scientists are still looking at available images and information to determine the category of hurricanes, for example. Its intensity is measured with the improved Fujita scale, which goes from EF-0 to EF-5 and takes into account damage caused by the passage of air columns.

At a news conference on Saturday, President Joe Biden said he would ask the Environmental Protection Agency and other relevant government agencies to investigate the potential contributions of climate change to the events.

“We know that everything is more intense when the planet gets warmer, and that obviously has some effect here, but it’s not possible to give a quantitative explanation for this yet,” he declared.

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