Extreme Weather Event: Rare December Tornadoes Kill 76 Across Four States

The White House has declared a state of emergency in Kentucky after a rare, late-season tornado outbreak that cut a swath of destruction 250 miles (400 kilometers) across Arkansas, Kentucky, Missouri and Tennessee, and confirmed to have killed at least 76 people. Tornadoes associated with the same weather system, referred to as the “Quad-State tornado”, are confirmed to have touched down in Illinois and Mississippi, and if confirmed, may include the longest-lived single tornado in US history—an event that struck during a season when the affected regions are typically more concerned about snowstorms than tornadoes.

The conditions causing the outbreak were a low-pressure trough that was traveling eastward across the US that interacted with the unseasonably moist and unstable conditions that were present across the Mississippi Valley at the time. This event produced a long-lived supercell thunderstorm that started in northeastern Arkansas in the late afternoon on December 10, spawning a family of tornadoes—and possibly just a single, long-lived tornado—that then cut across Missouri’s Bootheel region where it crossed the Mississippi into West Tennessee, then into Kentucky where it tore across the northern portion of the state; the supercell finally ran out of steam after crossing the border into Ohio in the early hours of December 11. If this event is confirmed to have been perpetrated by a single tornado, it will be the longest ever recorded, surpassing the 219-mile-long (352 km) track cut by the Tri-State tornado that tore through Missouri, Illinois and Indiana on March 18, 1925.

At least 76 deaths have been confirmed to have been caused by the tornadoes across the four states, with the death toll expected to reach 100. 70 are believed to have died in the city of Mayfield, Kentucky, alone; if this is confirmed, this would be the deadliest tornado in the state’s history. At least six were killed when an Amazon warehouse collapsed in Edwardsville, IL, an event that trapped between 50 and 100 workers inside the portion of the facility that remained intact.

A state of emergency has been declared in Kentucky, where counties across the northern portion of the state bore the brunt of the damage caused by the outbreak, with the city of Mayfield suffering catastrophic damage; “scores” of workers are feared to have been killed in the collapse of a candle factory in the community, with recovery efforts expected to extend early into this week to recover the workers still trapped in the rubble. Mayfield’s fire station and police station were destroyed by the storms, with several other structures sustaining serious damage, including the city hall building.

Further north, the same weather system prompted Minneapolis and St. Paul to declare snow emergencies, with some Minnesota towns receiving over a foot (30 centimeters) of snow from the storms; a snow alert was issued in Sioux Falls, South Dakota, with numerous highways across the state being covered in snow.

Scientists are warning that global warming is exacerbating the conditions that cause extreme weather events such as this; just last month Canada’s province of British Columbia and parts of Washington state were plagued by heavy flooding and landslides caused by record-breaking rainfall, brought about by an “atmospheric river”, a narrow air current containing a heavy amount of moisture, that crossed the region.

“A lot of people are waking up today and seeing this damage and saying, ‘Is this the new normal?’ ” according to Victor Gensini, a meteorology professor at Northern Illinois University, referring to the devastation caused by this weekend’s tornado outbreak. Although global warming is certain to cause stronger and more frequent extreme weather events, the impact of climate change on individual weather events is harder to determine. “It’ll be some time before we can say for certain what kind of role climate change played in an event like yesterday.”