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21May 2013

On the science of a very bad tornado

NOAA map of major tornado patterns

On Monday, a massive tornado plowed a near 20-mile path through suburbs of Oklahoma City, killing dozens of people and destroying entire neighborhoods. My purpose in writing about it here at the Tracker is to take a look at the ways that science writers helped illuminate the power of that storm. But stories of big storms are always first stories of devastated lives and I'd like to start by extending the sympathy and best wishes of all of us here to people in those damaged communities.

The tornado that struck in the region of Moore, Oklahoma yesterday was reportedly as much as a mile wide at points and reached peak wind speeds that topped 200 miles an hour. According to the National Weather Service, that classifies it as an EF-4 tornado on the widely accepted Fujita Scale. This is the second most powerful tornado classification on that scale; the worst is an EF-5, which can generate winds above 300 miles an hour. In 1999, in fact, a tornado with wind speeds measured at 302 miles an hour churned through this same stretch of Oklahoma. For an excellent perspective, Colin Schultz at has posted a piece called "How to Understand the Scale of the Oklahoma Tornado."

Does it mean anything that two of our worst tornadoes struck here? This region of Oklahoma lies in a section of the Great Plains, east of the Rocky Mountains, that is often referred to as "tornado alley" for the combination of geology and meterology that fosters storms in this region. You'll notice in the NOAA image that I used to illustrate this post that the agency has done a historical mapping of major storm events that shows the Oklahoma City area in the center of an irregular bullseye of tornado intensity. There's another version of this map, plus a wonderful amount of both historical and scientific perspective in a backgrounder by Alexis Madrigal at The Atlantic, titled "Tornadoes in America: The Oklahoma Disaster in Context." And also a really great Megan Garber Atlantic article on why storm cellars could have saved more lives - and why there aren't more of them.

Still as Alan Boyle and John Roach at NBC point out, many of the highest cost tornadoes, in terms of lives lost, have occurred in a region of the Southeast called "Dixie Alley", partly because southern tornadoes tend to strike more frequently at night and to move more rapidly. And as the BBC's Jason Palmer notes, knowing the high risk regions still doesn't mean that predicting such storms or their paths is yet an exact science.  Ker Than at National Geographic makes a similar point on the illusive nature of tornado prediction as does Brad Plumer at The Washington Post. (And we can underscore that by pointing out that it was only on May 9 that the weather service announced that tornado activity was at a 60-year-low.)

It's worth noting that we saw also saw stories on the frustrating nature of tornado prediction after a dozen tornadoes unexpectedly touched down in Texas last week, killing six people. As Elizabeth Harball and Evan Lehman reported in a story carried by Climate Wire, one of those tornadoes was also an EF-4 which reached more than a mile wide. The difference was that it spent less time on the ground and moved through a less densely populated area. But where it touched, it also destroyed. The Texas tornadoes prompted Marlene Cimons, of Climate Nexus, to post an op-ed at LiveScience on whether storm intensity was increasing as the planet's climate changes.

Cimons did  a thoughtful job of exploring that possibility and all the complications in making that case. And following the Oklahoma twister, Harry Enten at The Guardian has an even more indepth and wonderfully balanced look at the complicated relationship between global climate patterns and regional weather intensity. And over at Scientific American, David Biello has a smart Q&A on that subject with leading climate researcher Kevin Trenberth of the National Center for Atmospheric Research (not to mention a whole package on tornado science).

I know there are more excellent examples out there and I wish I had the time and space here to acknowledge all of them. I think good science writers shine in these stories - they take the chaos of a natural disaster and give it shape and order. And they add perspective - even the perspective of distance. In light of the later, I'd like to close by highlighting Phil Plait's post at Slate on satellite imaging of major storms, a space-based perspective on the risky nature of life on a restless planet. Plait closes with a list of organizations that are helping the tornado victims so if reading about the storm makes you want to do something more than explore its science, do read his piece right to the end.

-- Deborah Blum

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