Oklahoma is in a particularly busy and dangerous section of Tornado Alley, the cluster of states in the nation's midsection that are especially twister-prone.
If you map all the nation's tornadoes in May — the busiest tornado month — they form a circular blob 100 miles across over central Oklahoma. That's because low-pressure systems rush south down the Rocky Mountains and collide with warm, moist air, forming nasty thunderstorms that often spawn tornadoes, said Harold Brooks, a research meteorologist at the Severe Storms Laboratory in Norman, Okla.
"Welcome to the sweet spot of severe thunderstorms," Brooks said.
Texas, Kansas and Florida get more tornadoes than Oklahoma does, according to the National Oceanic and Atmospheric Administration. But Oklahoma gets more of the biggest ones — the EF5s, like the one that smashed Moore. That's why the storm lab and the National Weather Service storm prediction center are in Oklahoma, Lindell said.
With severe thunderstorms, you can get both tornadoes and flooding. Oklahoma has been declared a disaster 35 times because of tornadoes and 44 times because of flooding. In some instances, a combination tornado-and-flood disaster was declared.
The FEMA database looks only at how often catastrophes are declared and aid is shipped, not how much total money is given out.
Tornadoes generally occur more frequently than hurricanes and earthquakes but usually don't cause as much damage. Oklahoma City officials estimate the Moore tornado caused up to $2 billion in damage, while state officials say it may exceed the figures for the 2011 Joplin, Mo., tornado. At $2.8 billion, Joplin has been the nation's costliest tornado since 1950, according to NOAA's Storm Prediction Center.
Yet NOAA's National Hurricane Center lists more than 30 hurricanes that caused more than $2.8 billion damage when adjusted for inflation. Hurricanes tend to hit broader areas, last longer and strike the more densely populated coast, where property values are higher.