December tornado record crushed by historic storms
December, a month typically known for cold weather and snow, was instead marked this year by a historic barrage of violent thunderstorms and tornadoes.
No December on record has seen as many tornadoes in the United States as 2021, by a long shot. And no December has seen such a devastating toll on life.
Few areas of the central U.S. were untouched by severe storms, incited by the strong wintertime jet stream spreading over record-smashing temperatures more typical of springtime. The outbreaks of severe weather and swarms of tornadoes were not only unprecedented for December but would also be unusual at any time of year.
Here we summarize some of the key facts and figures.
December severe weather at a glance
While records are too numerous to list in one spot, these key points demonstrate how unusual the month’s severe weather was.
163 tornadoes have been confirmed, the most on record in December by far, and the second most in any winter month. The tornado count would be above average for any month other than April, May and June. The two main outbreaks alone were responsible for at least 145 of these tornadoes. The Weather Service has confirmed 66 tornadoes from Dec. 10 and 11 and 79 tornadoes on Dec. 15.
There have been twice as many strong tornadoes this December than in April, May and June this year. December is, on average, the month with the fewest tornadoes, while April, May and June average the most.
90 people have been killed by tornadoes in December, which now ranks as the 10th deadliest month for tornadoes since modern records began in 1950.
The severe thunderstorm complex that struck the Upper Midwest on the 15th was the first derecho on record in December, according to the National Weather Service, and it produced the most reports of wind gusts greater than 75 miles per hour of any known event.
There have been tornadoes on eight days of the (still ongoing) month, including one near Fort Myers, Fla. Tuesday.
The exceptional Dec. 10 tornado outbreak
The long tracks of the tornadoes that slashed across the zone from Arkansas to western Kentucky on Dec. 10 and 11 are atypical for any time of year. There is simply no precedent for such enduring twisters in December.
Two of the long-track tornadoes were spawned by a single rotating thunderstorm or supercell that crossed five states covering 300 miles.
The first of the two tornadoes associated with that supercell ripped through northeast Arkansas, southeast Missouri, and northwest Tennessee, becoming a rare ‘tri-state’ tornado, with a track length totaling just over 80 miles. The same supercell produced a second twister that was on the ground for an astonishing 166 miles, devastating Kentucky communities like Mayfield and Dawson Springs.
Just to the south, another long-track supercell produced a tornado that trekked over 122 miles through northwest Tennessee and southwest Kentucky.
Since 1950, only one other day has seen two tornadoes with tracks at least that long: April 27, 2011.