ANN ARBOR, Mich. – Typically, severe weather season in Southeast Michigan starts in late March, peaks in July, and runs through early September due to warmer weather, increasing moisture and humidity in the air. Historically speaking about 90% of our convective warnings issued in Southeast Michigan have been for severe thunderstorms concerning damaging winds and/or large hail as opposed to tornadoes. However, the damage from straight-line winds can be eerily similar to tornadoes when it comes to the amount of destruction.
I recently visited the wind tunnel at the University of Michigan to see what my body could withstand and was very surprised. Once the winds reached about 40-45 mph, I was fairly confident that I wouldn’t have been able to stand on my own two feet without the support of a harness. So what was the surprise factor? Severe Thunderstorm Warnings are issued when wind gusts reach 58 mph or if the storms are capable of producing hail 1” in diameter or greater. That means that winds well below the threshold of being considered severe could knock me off my feet and that would mean winds in that range (40-45 mph) would come without a warning.
Just like your body, there is a threshold for what buildings can withstand too. Dr. Seymour Spence teaches and studies the effects of high winds on infrastructure at the University of Michigan and says that damage begins to occur around 60 mph.
“Ultimately buildings will have direct wind damage due to pressures. The pressure can then build enough to create a loss of a roof panel, a siding panel then you can start to get internal pressurization which can lead progressively to the entire loss of a roof on a building,” adds Dr. Spence. “Keep all your doors and windows and garages closed. You do not want any air coming into your building. What’s going to happen? If you have an open door, windows open, pressure is going to build up inside your building and then you start to get positive pressure trying to actually rip components of your building.”