Monday afternoon and evening, several severe thunderstorm warnings were issued by the National Weather Service, and some of you heard your tornado sirens sound, even though there was no tornado warning. What gives?

We are all familiar with the tornado sirens:  When you hear one, you head to the basement or your place of safety as quickly as possible, because a tornado is either on the ground, or a severe thunderstorm capable of producing a tornado has developed.

However, siren philosophy has changed recently, and many communities and counties now also sound their sirens when a severe thunderstorm with anticipated 70 mph or greater wind threatens.

Why?  

Because a 70 mph wind gust from a thunderstorm is comparable to the wind in a weak tornado.

If the sirens are sounded for a weak tornado, why wouldn't you sound them for a severe thunderstorm with wind as strong as in a weak tornado?  70 mph plus wind can snap off large trees and power lines, and cause some structural damage ... they are very dangerous storms, so you should still seek shelter whenever you hear the sirens.

Back on July 2nd, 1997, a very severe thunderstorm roared through the Grosse Pointes with 100 mph straight-line wind gusts, blowing a gazebo with thirteen people in it into Lake St. Clair, killing five of them.  High-end severe storms even without tornadoes are still high-impact storms, so keep this in mind the next time you hear the sirens.