Normally cold months for tornadoes seem to be getting hot

The tornado outbreak across the South on Tuesday and Wednesday, along with another one weeks earlier, propelled November to the status of one of 2022’s most active months for twisters.

Although some twisters are normal in November, their number and ferocity this year were unusual. Ordinarily, tornado activity is most pronounced from mid-spring to the beginning of summer.

The November tornado outbreaks are reminiscent of several other out-of-season events in recent years. Last December brought unprecedented tornado activity for the time of year.

The recent flurry of tornado events – outside the bounds of what is normal – is raising questions about how climate change could be shifting twister behavior.

January and February were characteristically quiet for tornadoes in the Lower 48 states before activity flared up in March

An outbreak on March 5 struck Iowa, with one particularly long-tracking and violent twister on the ground for nearly 70 miles. The tornado, which killed six, was rated an EF4 on a scale that goes up to 5; it was the strongest tornado ever recorded so far north so early in the year.

That outbreak was followed weeks later by two others, on March 21 and 30. Both were prolific twister producers, and that March became the most active on record for tornadoes.

But as mid-April turned to May and June, the tornado outbreaks all but ceased, producing a lull that coincided with what is normally the most active time of year. By May’s third week, the 2022 tornado count had sunk below average; by mid-July, it had plummeted beneath the 25th percentile.

Then, November arrived. On Nov. 4, a powerful line of rotating thunderstorms produced a swarm of damaging tornadoes in Texas and Oklahoma that included two rated EF4 and two rated EF3. Nov. 4 was just the third day since 2014 to see multiple EF4 or EF5 twisters.

The outbreak across the South on Nov. 29 and 30 produced two EF3 tornadoes – one of which scoured deep ruts in the ground, along with dozens of weaker twisters.

On average, the 11th month of the year has one of the lowest tornado counts, and March, while relatively active, has counts that pale in comparison to April, May or June.

Although 2022’s tornado activity has departed from the norm, it falls along the lines of recent years. The autumn months of 2021 also were uncharacteristically active, with a near-record tornado count in October and an unprecedented December of twisters. That year also saw a secondary maximum of tornadoes in March, but a relative dearth of twisters in April, May and June.

Similarly, 2020 brought destructive early-year outbreaks that gave way to a below-average May and June.

In 2018, the biggest day for tornadoes was in October and the third-biggest was in December. All three of the most significant twister events in 2017 occurred in the first week of March, while the two days with the most tornadoes in 2016 were in February and November.

The heightened March activity over the past few years could be related to the presence of La Niña. Research has tied La Niña events – in which the Pacific Ocean near South America is cooler than normal – to intensified early-spring tornado activity.

Some research also supports the idea that global warming could be promoting more-severe weather in colder months by increasing the warm, humid air that fuels storms when such air is normally absent.

As for the lackluster activity in the later spring months in recent years? With little research linking either climate change or La Niña conditions to twisters in May and June, it may just be luck.