It’s “only” a thunderstorm warning? Really?

“It’s only a thunderstorm warning.” Have you ever said that? Have you ever heard anyone say it?

Complacency about severe thunderstorms is dangerous but common. Why is it dangerous? Non-tornadic thunderstorm winds killed two people in northern Indiana last year. Throughout Indiana, they killed 32 people from 1990 to 2014 (see graph above). Non-tornadic (“straight line”) severe thunderstorm winds killed all 32. Tornadoes were not involved in any of those deaths.

If you believe you’re not in danger as long as there’s no tornado, you could be the next victim.

What might surprise you is that the winds of a severe thunderstorm can be stronger than those of a tornado, and often are. For example, an EF1 tornado on the Enhanced Fujita scale produces tornadic winds of from 86 to 100 mph. The “derecho” line of severe thunderstorms that struck northern Indiana in June of 2012 produced a measured wind gust of 90 mph at the Fort Wayne international airport. That’s stronger than the bottom end of the EF1 tornado range!

What can a 90 mph wind gust do? According to the Beaufort wind scale that storm spotters use to estimate wind speeds, 90 mph wind can do considerable and widespread damage to structures.

The northern Indiana office of National Weather Service ( NWS) issued 114 severe thunderstorm warnings in 2014. Such warnings might therefore seem quite common, which can lead to complacency. It’s important to know, however, that the NWS issues those warnings only when a storm is producing or is expected to produce either one of the following:

• Wind gusts of 58 mph or stronger
• Hail of one-inch or more in diameter

Winds of 58 mph can uproot trees and do considerable structural damage. One inch hail can be traveling at 100 mph when it hits the ground (or your house, car, or worse, your head).

So, the next time the National Weather Service issues a severe thunderstorm warning, take shelter, just as you would for a tornado warning. Don’t become the next person on the state’s tally of non-tornadic thunderstorm wind deaths!