Why the South gets more deadly tornadoes at night

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By SETH BORENSTEIN AP Science Writer

Forget “The Wizard of Oz”. Tornadoes cause far more death and destruction in eastern and southern Kansas these days. And they often do it in the dark of night.

Tuesday night’s deadly tornado that hit the New Orleans area is the perfect example of what experts say is the tornado problem of the 21st century: Killer tornadoes have moved a bit from the vast void of the Great Plains , more in the southeast where there are more people to hit, poorer populations, and more trees to hide tornadoes from view.

And as if that weren’t enough, these southeast tornadoes are more likely to strike at night when they’re more dangerous.

Here’s a look at what’s behind the change:

Why do tornadoes kill more people outside the Great Plains?

Since 2000, nearly 89% of the 1,653 Americans killed by tornadoes — not counting victims this week — lived east of the Dakotas, Nebraska, Kansas, Oklahoma and Texas, according to an analysis by Associated Press data from the National Oceanic and Atmospheric Administration.

Last year, 100 people were killed by tornadoes in Kentucky, Alabama, Illinois, Tennessee, North Carolina, Arkansas, Missouri, Louisiana, Mississippi and Pennsylvania. One person was killed in Texas.

It’s not so much a weather problem as a people problem, tornado experts said.

“It’s a function of the human-made environment,” said Victor Gensini, a professor of meteorology at Northern Illinois University who specializes in severe storms. “The Mid-South gets a lot of tornadoes, but in the Mid-South we have more things to hit. We have more bull’s eyes on the dart board. We have more cities. We have a weaker frame housing stock. Tornadoes happen more often there at night, which is exactly what we saw last night.

Harold Brooks, a senior scientist at NOAA’s National Severe Storms Laboratory, said traditional 20th-century tornadoes, the type Oklahoma and Kansas are famous for, are less deadly because they travel for miles without obstructing anything. In 1991, he and his wife chased a 66-mile tornado in Oklahoma whose winds reached 286 mph. It hit two barns; no one except a few cows was injured.

Put this storm near New Orleans at night and dozens of people would be killed, probably many more. In the southeast, “all it takes is one weather event and you’ll have people in the way,” Brooks said.

Does climate change have a role?

In 2018, Brooks and Gensini published a scientific study showing that fatal tornadoes occurred less frequently in Oklahoma, Kansas, and Texas tornado alley and more frequently in “fatal tornado alley, which is the Mid-South,” Gensini said.

What is likely happening is that the West is getting drier due to human-caused climate change, making the air more difficult to become moist and unstable, which is crucial for tornado formation, they said. The southeast receives warmer air, which contains more water vapor, which creates this significant instability, Gensini said.

Climate models predict this type of change in about 50 years, but it appears to be happening now, Gensini said.

But Gensini, Brooks and Jana Houser, professor of meteorology at Ohio University, stressed that they saw no signal of climate change in Tuesday’s deadly tornado in Louisiana.

There is a La Nina, a natural periodic cooling of parts of the Pacific that changes global weather patterns, and that usually means more tornadoes in the Southeast due to changes in the jet stream and humidity, have they stated.

How are nocturnal tornadoes different?

Tuesday’s nighttime tornado illustrated a problem because when tornadoes hit at night, people can’t see them coming as easily and often don’t react as well, tornado experts said.

About three-quarters of the tornadoes that hit Oklahoma and other Great Plains states happen between 5 p.m. and 9 p.m. so people know when to expect them and it’s brighter, Brooks said. But in the Southeast, they can strike anytime, which means more often at night than in Oklahoma, which makes them more dangerous.

Another reason they happen more at night in the southeast is that they happen more in the spring and there are just fewer daylight hours, Gensini said. Spring storms are juicier and stronger than summer ones, so they don’t need daytime heat from the sun to add that extra energy to spur tornadoes, he said.

What about the landscape?

The southeast is also affected by the presence of more trees, hills and buildings that block people’s view of the coming storms.

When there’s a tornado warning in the Southeast, often people are “on their porches and they really can’t see anything, and it looks like, you know, dark skies,” Houser said. “They may be less likely to heed these warnings than if they come out of their house and see a tornado on the horizon, even if it’s far away. So there’s a bit of geography that plays a role there.

Good news for the region?

The only benefit of tornadoes in the Southeast is that they allow meteorologists to predict conditions for bad outbreaks earlier. Tuesday’s severe storm was warned about eight days in advance by NOAA’s Storm Prediction Center, which is unusual, Brooks said.

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