Aug
13
2007

The damage, they say, is blowing in the wind

Timber: Strong winds that form out of thunderstorms can topple huge trees pretty quickly.
Timber: Strong winds that form out of thunderstorms can topple huge trees pretty quickly.
We had the nastiest storm of the season in the Twin Cities early Saturday morning. When I awoke to check the windows in my apartment, I was surprised to see what was happening. My windows face the south and east, and it appeared that items were being sucked toward the east-facing windows.

The storm was intense enough that I still closed the windows. But I was struck how there seemed to be a reverse pressure sucking air out of my apartment.

Today, I had the time to check around the Internet to learn a little bit more about winds associated with thunderstorms. I’ve learned some things from the TV meteorologists about straight-line and downburst winds. They can actually be more destructive than many tornadoes. Here are some things to keep in mind as we ride out the rest of the summer storm season.

Straight-line winds can be identified by the wreckage that shows no rotational damage. That is, all of the damage is generally blown down in the same direction. The big-blow down storm in the Boundary Waters Canoe Area several summers ago is a classic example of that. Trees were all toppled the same way. Tornadoes, on the other hand, will scatter debris in all directions.

What I learned on my new search today was an effect known as “plough winds.” These are the strong downdrafts that can come out of thunderstorms, sometimes peaking out at 60 to 90 miles per hour. The air goes straight down from the thunder clouds, strikes the ground and gushes out horizontally, just like water splashes out from a tap. Their damage is often confused for tornado action as well, but the debris paths will have a star pattern to them, rather than a tornado’s twists and turns.

Getting back to my apartment windows Saturday morning, I’m sure some plough wind or straight-line wind was blowing away from those windows, creating a vacuum behind it and sucking stray papers toward the window screens. Am I right?

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