Below is a blog originally post at wset.com in July 2012.
Wind damage from thunderstorms is a common occurrence in Virginia. Most of the time, the wind is from a rapidly moving downdraft. Cooler air from inside a thunderstorm races downward and hits the ground, spreading out in many directions.
Those winds get bumped and bristled through neighborhoods and wooded areas, where they form small twists and eddies, like water racing through rocks in a creek. These damaging winds often run 40 to 60 mph, bringing down some trees. Or, they can briefly surge to 70 mph, damaging roofs or poorly constructed buildings. Some of the worst of these downdrafts, called microbursts, can have winds near 100 mph.
An EF-0 tornado has winds 65 to 85 mph, an EF-1 tornado has winds 86 to 110 mph. So the wind speeds are comparable. Tornadoes generally require a deep circulation inside of a thunderstorm, and that initial circulation is not found in every thunderstorm. In fact, in July and August, the winds aloft are so weak, those circulations are rarely found at all.
An 80 mph wind is going to do damage, whether it is spinning or not. I have never understood why some people get so upset if told by a professional meteorologist that their damage was caused by non-tornadic winds.
Does it cheapen the damage? Make it any less real?
The first big storm we are told about as children is the tornado. Its cousin, the hurricane, is big, slow, and easy to see coming. Not a tornado. It moves in, does its damage, and is gone in a matter of minutes. For that reason, tornadoes are terrifying. They are ingrained in our weather culture and folklore. The Wizard of Oz did not feature a microburst. Maybe that’s part of it.
Some clouds look like tornadoes. Wall clouds are often a culprit. Moist downdrafts and scud clouds can also look tornadic from a distance.
The brain can trick us. My favorite example is the Cat Scale sign I often see from the nation’s highways. From a distance, it looks like the face of a cat. But up close, the letters jump out, and the illusion is exposed.
Meteorologists want to get it right for historical purposes. That’s why photos are taken and surveys are done at the storm site. Gather as much physical evidence as possible and get it in the data base.
Believe me, we want to document them all. But sometimes, their mark is just not there.