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Tornado Alley in the Plains is an outdated concept. The South is even more vulnerable, research shows.

Twisters in the South and Southeast are just as common as in the Plains, and often more deadly.

Average path length of tornadoes within 25 miles of a point. Note that while the greatest density of tornadoes occurs in Oklahoma, tornadoes in Mississippi carve longer tracks, and the risk of being impacted there is greater. Tornado data between 1950 and 2018 was utilized. (P. Grady Dixon)
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Anyone who’s ever seen the movie “Twister” is aware of Tornado Alley — known for its reliable and, at times, hyperactive swarms of tornadoes that swirl across the landscape like clockwork each spring. The term brings to mind the strip of land stretching across Texas, Oklahoma, Kansas, Nebraska and the Dakotas. But meteorologists fear that imaginary zone may be leaving out areas at an even greater risk for damaging tornadoes.

Tornado season may ramp up again in late May

In recent years, the South has come to prominence for its encounters with violent tornadoes. As recently as Easter weekend, an outbreak of more than 150 tornadoes wrought havoc across Mississippi, Alabama, Georgia, Tennessee and even into the Carolinas. A week later, a high-end EF4 tornado struck near the previous hardest-hit counties in Mississippi, marking the third EF4 to hit within a 15-mile radius over the course of seven days.

Last month was the second-most active April for tornadoes

Meteorologists argue this corridor of enhanced tornado activity across the South isn’t just another tornado hot spot — it’s a bona fide extension of Tornado Alley. In fact, many atmospheric scientists say the term “Tornado Alley” is a misnomer and fails to convey where the greatest tornado risks may lie. Some contend portions of the South are among the most vulnerable to tornadoes in the world.

A troubled history with tornadoes

April 27, 2011, was a day that will live in meteorological infamy. A morning squall line of vicious thunderstorms plowed across Mississippi and Alabama, unleashing a band of quick-hitting tornadoes and winds that knocked out power to a million homes. An EF3 tornado hit Cordova, Ala. — a town that would be struck hours later by an even more violent tornado. Tornadoes are rated on the 0-to-5 Enhanced Fujita scale.

The atmosphere reloaded that afternoon, giving rise to what’s often regarded as the most prolific tornado outbreak in recorded history. Repeated rounds of violent tornadoes, including four EF5s, resulted in hundreds across Mississippi and Alabama as seemingly endless rotating supercell thunderstorms marched across the state. Some storms traveled hundreds of miles. All told, more than 350 tornadoes accompanied the days-long outbreak.

Already in 2020, tornadoes have struck Nashville; Birmingham, Ala.; Atlanta; Chattanooga, Tenn.; and Charlotte — making this year to date the deadliest for tornadoes since 2011. Mississippi recorded its widest tornado on record.

2.25 mile wide Mississippi tornado was nation's third largest on record

Most of the deaths from tornadoes have occurred outside the traditionally regarded Tornado Alley but well within the zone of where vicious tornadoes are common. Some experts agree it’s time to abandon the term.

Where do tornadoes occur?

“To be honest, I hate the term ‘Tornado Alley,'” said Steven Strader, an atmospheric scientist at Villanova University specializing in severe weather risk mitigation. He says he hates even more the term “Dixie Alley,” used to describe the busy swath of tornado activity in the South.

“What people need to understand is that if you live east of the continental divide, tornadoes can affect you,” said Strader.

The geographical distribution of tornadoes across the Lower 48 has been the subject of investigation for years. One study conducted by P. Grady Dixon, a physical geographer at Fort Hays State University in Kansas, found that the Deep South is in essence a continuation of the more traditionally recognized Tornado Alley.

“I’m of the opinion that Tornado Alley is an outdated, misleading concept in general,” said Grady in an interview with The Post. “But I’m realistic in that I know [the term] is not going away anytime soon.”

His project found, on a basis of tornado density and path length, the most tornado-prone location in the country isn’t in Oklahoma or Kansas — it’s Smith County, Miss. Though Grady’s paper was published in 2010, anecdotal evidence since suggests his finding is spot on: That region of Mississippi has been close to ground zero for the country’s worst twisters so far this year.

On the whole, Grady’s work revealed not only that Mississippi and Louisiana average the most “tornado days” per year, but that an enormous circular swath from the Midwest and Corn Belt down through the Plains and South are one large breeding ground for tornadoes.

Save for a small downtick in tornado counts over the Missouri and Arkansas Ozarks, there’s virtually nothing separating — or distinguishing — traditional Tornado Alley from the South.

“The term ‘alley’ is restrictive, suggests something that is spatially long and narrow so to speak,” explained Grady. “We have a tornado region that’s essentially the eastern 40 percent of the continental U.S.”

“Even just that paper, we’ve learned tons of things,” Grady continued. “I don’t think a gap [between the Plains and the South] exists. … Maybe there’s a low spot in activity in Missouri, but if you’re drawing a line from central Mississippi to south central Kansas, there’s no gap. Central Illinois to eastern Nebraska, there’s no gap. They’re connected.”

Deep South tornado dangers

To make matters worse, Grady uncovered evidence suggesting tornadoes in the South, or Dixie Alley, travel farther thanks to their faster speeds. Those longer paths make tornadoes more likely to cause damage in the South, especially before the mid-spring and summer months and again later in the fall.

“Storms tend to move faster during the cool season,” Grady said. “I think they are actually longer [tornado] paths throughout the Deep South. Look at the speeds of some of these storms from that Easter event. … We were having some storms move at 70 mph.”

Two strong tornadoes may have merged over South Carolina during Easter outbreak

Tornado are also as common — or even more frequent — in the South as they are on the Plains. “That region gets probably the greatest number of tornadoes, the Southeast,” Strader said.

So why has Tornado Alley’s colloquial definition never really included the South? It boils down to public perception, rooted in years of storm chasing, cinematography and geography.

Public perception of tornado risk

Our subliminal association of only the Plains as Tornado Alley largely predates us — originating in the early days when tornadoes began appearing on television and in print media.

“We’ve all seen ‘The Wizard of Oz,’ and we’ve all seen the tornado dancing in the landscape, the sepia tornado in the wheat field,” Strader said. “We associate tornadoes [with the] central half of the U.S.”

It’s likely a product of the imagery we see. Often, the most compelling videos of tornadoes — which routinely make the evening newscasts — come from flat landscapes with few trees to obscure the view. That’s Kansas, Oklahoma and the Texas Panhandle in a nutshell. The forests of Mississippi, Louisiana and Alabama? Not so much.

Thunderstorms along the Gulf Coast generally form in highly humid environments, resulting in lower cloud bases that can obscure a storm’s structure. Heavy rainfall frequently shrouds any tornadoes that do form. They’re rain-wrapped twisters impossible to photograph. Moreover, thunderstorms in the South are usually quicker-moving.

“With lower cloud levels and [faster storms], essentially they don’t see the tornado coming until it’s right on them,” Strader said.

In addition, timing of storms may play a role. Oklahoma, for instance, sees nearly two-thirds of its tornadoes during April and May, the bulk of them occurring during large outbreaks that attract media attention. While the South sees increased activity in the spring, its accumulation of tornadoes is more spaced out over the entire year with a second season in the fall.

“Who was providing photos and videos of tornadoes? Experts and extreme enthusiasts,” Grady said. “They built their [expeditions] around going to the Great Plains because of that reliable season.”

“But the South [has] one really long season that runs from September to May, but they sort of get the summer off,” said Grady. “Their season is less predictable. It tends to lull people to sleep. It’s very inconsistent year to year.”

Defining tornado risk

Regardless of where the jackpot of tornadoes may form, experts agree that tornado risk ought to drive discussions on tornado safety and preparedness.

“What I like to tell people is tornado disasters are a coin,” Strader said. “Tornadoes are one side of that coin, and societal influences are the other. When we’re looking at tornado disasters, we don’t care about tornadoes in middle of a field. We care about the one that goes through a subdivision. So often, we’re neglecting the societal side.”

Strader says that while tornadoes routinely terrorize Oklahoma, the bull’s eye for tornado risk and fatalities is in the South. “What it comes down to is the difference in the socioeconomic structure of the two regions,” he explained.

Dissecting the Deep South’s tornado risk

Urban sprawl, housing type and land use all work together and culminate into a bad recipe for high-fatality tornado events in the South and Southeast. Population density is also much greater, expanding the target for tornadoes — particularly east of the Mississippi River.

The greater population density has ties to the way land is used in the Southeast, according to Strader. While the Plains is largely farmland and inhibits the spread of neighborhoods and communities, the South, albeit rural, doesn’t “really have that strong [of an] agricultural tie anymore,” Strader said.

“That allows population of South and Southeast to sprawl out a little easier,” Strader explained. “When a tornado does occur in either region, odds are much greater in the [South of Southeast] of it hitting something.”

In addition to the greater population density, many people who live in the South reside in mobile or manufactured homes. It’s no secret these types of homes can become death traps during tornadoes and succumb to even lower wind speeds. Contrary to popular belief, however, it’s not the building’s structure itself — but rather how it’s anchored.

“What we have found in manufactured homes where fatalities occur is that the box, the superstructure … itself is good," Strader explained. "It’s as good as a single family home.”

The issue, he says, is with anchoring.

“Probably 95 percent of fatalities in manufactured homes occur because the first component of failure isn’t the home itself,” Strader said. “It’s the anchoring to the ground.”

In the aftermath of Hurricane Andrew in 1992, the Federal Emergency Management Agency required mobile homes along the Gulf and Atlantic coasts to be anchored according to “Zone 3” standards, which Strader believes would dramatically increase a mobile home’s survivability during a tornado. He estimates anyone can bring their home up to snuff for less than a thousand dollars.

Of course, your first course of action during a tornado should be to seek shelter below ground. But some people may wonder why so few mobile or manufactured home communities have community shelters. Strader says it’s not so simple.

Mobile and manufactured homes are “everywhere in the landscape,” he said. “Everywhere else in the country, when you see a mobile or manufactured home, it’s in a park. You don’t have that necessarily in the Southeast. Eighty percent of mobile or manufactured homes are found in the landscape [by] themselves.”

It’s a construction type that is a staple of many Southern communities.

“There are counties with no mobile home parks at all, but yet 60 percent of their residents are in manufactured housing,” Strader said.

That prevents the construction of community shelters; without a centralized location near to everyone, the utility of a community shelter would plummet markedly.

“In the Southeast, it’s not a great solution. If everybody’s 20 minutes from [a community shelter] but average warning [lead] time is 12 to 13 minutes, they’re not going to get to it,” said Strader.

Putting it all together, the shortage of sheltering options — coupled with swelling population and expanding targets — has made the South the leader in tornado fatalities. Add to that the public’s tendency to delay shelter and seek visual confirmation of a tornado, most of which can’t easily be spotted in the South, and you have a recipe for disaster.

The bottom line

In the end, Strader and Grady are optimistic that society is finally becoming aware of how outdated a concept Tornado Alley is. They hope awareness of the much more widely present tornado risk stretching from the Plains into the Midwest, South and Southeast is on the rise.

But Strader says the South’s tornado vulnerability also is on the rise and looks to get worse as urban sprawl continues. If that happens, tornado disasters don’t look to go away anytime soon.