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Researchers ponder why Friday’s tornadoes led to so many deaths, despite ample warning

A destructive tornado tore through Mayfield, Ky., and three other states on Dec. 10 and 11. (Video: Brandon Clement)

Despite accurate forecasts and timely warnings, Friday night’s tornado outbreak was December’s deadliest on record. Researchers of many stripes, from engineers and forecasters to social scientists, now face the burning question: Why?

Experience from past tornado disasters assures that the answers will be complex and multidimensional, taking months if not years to pin down.

But the evidence suggests the timing of the tornadoes, coming in the dark of night, their exceptional intensity and the population density of the region hit were all key factors in the catastrophe — which advanced warning could not overcome.

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The storms shouldn’t have been a surprise. From long-range outlooks to immediate warnings, there was ample notice that trouble was brewing. In the predawn hours Thursday, more than 36 hours before the first twisters developed, the National Weather Service Storm Prediction Center placed the hardest-hit areas under a level 3 out of 5 risk of severe weather, later upgraded to level 4. The center noted that “several tornadoes, some strong, will be possible.”

Sharla Payne describes what it was like to be inside the Mayfield Consumer Products candle factory in Mayfield, Ky., when a tornado hit on Dec. 10. (Video: Drea Cornejo/The Washington Post)

Most of the four-state zone ravaged by the tornadic storm, from northeast Arkansas to western Kentucky, was covered by a tornado watch at 3 p.m. Central Friday, hours before it even formed. At 6:22 p.m., a Weather Service discussion noted the formation of what computer models had projected as a potential long-lived tornado producer. The center warned that “sustained, strong tornadoes are possible in the next few hours” over the quad-state area.

As the rotating storm began causing mayhem, strongly worded Weather Service tornado warnings gave downstream residents advance notice, often on the order of 30 minutes. Weathercasters and meteorologists on social media amplified these messages, stressing the unusual danger of the setup.

For tornado researchers, watching a near-certain calamity unfold was a sobering experience.

“When you have a violent, long-tracked tornado traveling at highway speeds overnight, in December … it’s quite literally a recipe for disaster,” wrote Stephen Strader, an assistant professor and director of the geography program at Villanova University, in an email. “It overwhelms the systems we put in place to protect people.”

December tornadoes aren’t rare, but Friday’s outbreak was something totally different

Ultimately, even the best warnings can’t eliminate the inherent danger of an outbreak as widespread and intense as Friday’s, Strader noted.

“Adequate warning does not always ensure that people will take shelter, can take shelter, or know the quality of their shelter (home),” Strader wrote. “When this fails, all we can do is hope the structures they are in are sturdy enough to withstand the tornado. Unfortunately, many are not.”

The outbreak’s timing made it particularly perilous: It intensified and peaked after dark. For anyone at risk who might have doubted that a truly catastrophic tornado was approaching in December, the darkness made it much harder to confirm the threat with their own eyes.

A landmark 2008 paper led by Walker Ashley from Northern Illinois University found that nighttime tornado deaths were not declining as rapidly as daytime deaths, thus heightening the relative after-dark threat. In fact, overnight tornadoes were 2.5 times more likely to kill than twisters during the daytime.

Strader is now working with Ashley and colleagues on an update to that paper, which had found that nighttime tornadoes — about 26 percent of the total from 1985 to 2005 — accounted for more than 42 percent of tornado deaths in that period.

Strader estimates that some 40,000 people were under the path of the quad-state tornadic storm’s radar-indicated rotation (or mesocyclone). The associated tornado path would be somewhat narrower.

Much of the area hit by the quad-state tornadic storm lies within the service area of the National Weather Service office in Paducah, Ky. The area was a standout in a national survey on how people across the country receive, comprehend and respond to tornado warnings.

The results, published in a 2020 paper and on a dedicated website, found that the average respondent in the Paducah area scored higher than the national average on a basic test of what tornado watches and warnings denote. That performance placed the area in the top five among more than 100 Weather Service areas.

Responding to a tornado threat when away from home

Even with knowledge at hand, people are often constrained when a tornado approaches simply by their current location. There’s been much attention paid to how people respond at home when a warning is issued — finding a small interior room, for example, or leaving a manufactured home — but less attention paid to what happens in a workplace or a store.

An increasing number of schools and businesses in the South have begun to shut down on springtime afternoons and evenings when an especially intense severe weather threat is predicted. However, the custom has been slower to spread to other times of day and other times of the year.

In both the Amazon warehouse in Illinois and the Mayfield, Ky., candle factory, where many people died, there were reportedly designated tornado shelters or shelter areas accessed by a number of employees. Yet multiple people still perished at those workplaces. That’s not a complete shock, given the obvious destruction, but it’s still a gnawing challenge for those who study tornado response.

“We’re often thinking about trying to reach individuals who have control of their settings,” said Kim Klockow-McClain, a meteorologist and social science researcher at the University of Oklahoma and the National Severe Storms Laboratory. “We think of them at home. That’s a static view of vulnerability.”

“When people go to work or to a business, it’s situational vulnerability — the situation you find yourself in when a tornado occurs.”

Klockow-McClain is part of a multi-institutional study of how businesses approach the severe weather threat when armed with the kind of probabilistic tornado warnings now being developed by the Weather Service. According to the authors, it’s the first time research on the new warning paradigm has been extended from the residential to the commercial setting.

In two recent papers on the project, the team reported that entities surveyed in North Texas seem to grasp the value of probabilistic information: “Our results suggest that when probabilities are added to the warnings, response mirrors the threat and allows businesses to make better informed decisions on when and how to respond.”

Despite his dismay over the toll of the December outbreak, Strader is encouraged by a community’s ability “to rally around each other” and bounce back.

“From a science standpoint, this presents an opportunity to learn and improve survivability with future events,” Strader wrote. “The coming months will reveal details [on the outbreak] stretching from meteorology to climate change to engineering to emergency management. Time will tell.”

Complete coverage: Tornadoes hit several states, killing dozens

President Biden arrived in Kentucky on Wednesday to survey the swaths of damage in areas hardest hit by a string of tornadoes that killed at least 74 people there and 14 in other states.

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Climate: Researchers ponder why Friday’s tornadoes led to so many deaths, despite ample warning