With summer underway, there’s something more dangerous in the air than sunburns and bee stings—tornados. While I’ve always associated tornados with Wizard-of-Oz whimsy, the word “tornado” has a different ring for many Americans, invoking horror instead of whimsy. As devastating as tornados can be, they are also fascinating meteorological events—that is, when observed from a distance.
What’s Up with the Weather?
Tornados are vortices of wind that occur in or below a cloud and occasionally touch ground. Since tornados are simply air, they would be invisible if not for the dust (and occasionally the cars, cows, and houses) they kick up. We normally imagine tornados as a single vortex of dust (these are officially titled “dust-tube tornados”), but tornados have several meteorologically-recognized forms, including “waterspouts,” which occur above large lakes or oceans and suck up tubes of water instead of dry debris.
Meteorologists measure tornado severity using the Fujita scale (after Ted Fujita, who designed the scale with Allen Pearson in 1971). The Fujita scale assigns tornados a grade between F1 (“moderate tornado”) and F6 (“inconceivable tornado”) based on wind speed and damage.
- With wind speeds ranging from 73 to 112 mph, an F1 tornado can peel the roofs off houses and overturn cars and mobile homes.
- An F2, or “significant tornado,” involves winds from 113 to 157 mph, causing considerable damage, demolishing mobile homes, and uprooting trees.
- An F3 is a “severe tornado.” Its 158 to 206 mph winds would tear the roofs and walls from even well-constructed houses, overturn trains, and uproot entire forests.
- An F4, or “devastating tornado,” is seriously bad news. With 207 to 260 mph winds, an F4 tornado would level houses, blow large buildings around, and create “large missiles” of flying cars and other objects.
- An F5, or “incredible tornado,” is the most extreme recorded level of tornado. An F5 involves wind speeds of 231 to 318 mph and would lift houses (and carry them significant distances), debark trees, toss vehicles, and damage even steel-reinforced concrete buildings.
- The mythological F6 tornado, which would occur with wind speeds over 319 mph, is highly unlikely. The damage by F6 winds would be hardly relevant amidst surrounding F4 and F5 damage. Engineering studies would not necessarily be able to document this tornado. Rather, they might classify it as a family of F4 and F5 tornados.
