When talking destructive tornadoes, one must mention Texas. The massive state suffers the highest annual average number of twisters in the nation, with storms spawning horrors that have erased entire communities.
But would it surprise you that, compared to many places in squally Texas, the District of Columbia and suburbs like Fairfax and Prince George’s counties are equally as exposed to tornado damage?
That’s according to a fascinating “tornado-vulnerability index” from Ethan Rogers, a 19-year-old meteorology student and tornado chaser who created the project for his GIS class at Penn State.
Lashed in warning colors of orange and red, the index identifies every U.S. county’s vulnerability to life and property loss caused by twisters (except in Hawaii and Alaska). It reveals several surprising things, such as that Baltimore is more at risk than northwest Oklahoma and that sections of the Florida coast are safer than the bitter-north finger of Maine.
Rogers was inspired to build the index after an EF-4 tornado hit Alabama on March 3, leveling homes, tossing cars like toys and killing 23 people. “I asked myself the question of who is most at risk to these types of tornadoes,” he says. “So many of those casualties were people who did not have a lot of money or lived in a mobile-home park.”
The index is not intended for a single person to consult to see if they will be hit by a tornado. Rather, it shows the possible impact to a county as calculated by four equally weighted factors: mean tornado frequency and intensity, population density, mean income per household and concentration of mobile homes. (The data comes from the National Weather Service’s Storm Prediction Center and the U.S. Census Bureau.)
“I picked all of these metrics because I believe that each one of them plays a major role in how much life and property is lost in the event of a tornado,” Rogers says. “The problem is not just a meteorological problem, it's also socioeconomic. Those who are poor and who can't afford houses that are structurally sound — or have basements or even shelters — are in much more danger.”
Information on income and housing was the “economic portion of the map that really made it what I wanted it to be,” he says. “I felt this data was important because counties that are poorer have fewer resources and less money to spend on resources to not only make households safer, but also recover in the event of a disaster.”
So what’s the most vulnerable region of America? That’d be the South’s notorious Dixie Alley, where the stats for 2019 already show a heavy dose of killer storms. “With a dangerous combination of a storied history of dangerous tornadoes, somewhat dense population, density of mobile homes and people in poverty, it’s no surprise that [this region] is vulnerable to tornadoes,” Rogers says.
Other high-risk places include Oklahoma and New Mexico, the latter having patches of deep poverty and hives of mobile homes.
Washington and its surrounding counties are immersed in a blob of moderate vulnerability, the third most-serious tier on the index. “That’s mostly because those areas are among the most densely populated areas in the country,” Rogers says. The region also sees “weak tornadoes — more frequently than one might think. As we saw with La Plata [in 2002], a strong, damaging tornado is not unheard of in that area.”
Cities are often ranked as more vulnerable because of their dense populations. Perhaps surprisingly, the index identifies the most vulnerable city in the United States as Chicago, because of its dense population, relatively low income (especially on the outskirts of town) and frequent visitation by tornadoes. “The Oak Lawn Tornado in the ’60s shows just how prone Chicagoland is,” he says.
Rogers hopes to add even more metrics to his index and bring it to the attention of emergency managers and local governments, especially those in the South and Southeast. “I understand it is impossible to completely negate loss of property and life altogether,” he says. “But millions of people are not well prepared for a disaster.”