A swarm of tornadoes tore through parts of Illinois on Saturday, destroying several dozen homes and damaging hundreds more, particularly in the town of Taylorville, about 25 miles southeast of the state's capital, Springfield.
As of the time of this column, 26 tornadoes had been confirmed by National Weather Service damage surveys from Saturday's severe weather in central and southern Illinois.
The interior of a home is visible the day after a tornado blew it off its foundation in Taylorville, Illinois, Sunday, Dec. 2, 2018.
(Ted Schurter/The State Journal-Register via AP)
This broke the record for the most tornadoes in any Illinois December outbreak, previously 21 tornadoes spawned in a destructive Dec. 18-19, 1957 outbreak, according to the NWS office in Lincoln, Illinois.
Unless you live in Florida, Southern California or the Caribbean, December brings thoughts of snow and cold, so let's explore how a tornado outbreak flared up in Illinois in this month.
The Ingredients
There is certainly a peak time of year for tornadoes in the U.S. – typically from April through June.
However, tornadoes can be spawned any time of year when the right conditions overlap. Over a 20-year period from 1997 through 2016, the U.S. averaged 31 December tornadoes per year.
In Saturday's case, a bullish swirl of low pressure aloft was spinning over the Missouri Valley near St. Joseph, Missouri.
A strong jet stream rounded the base of that upper low from the Red River Valley of Texas, punching northeastward into the mid-Mississippi and Ohio Valley.
Closer to the surface, a complex frontal system was tapping milder and somewhat more humid air northward from the Deep South into central and southern Illinois.
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