At this time of the year, we hear a lot about tornadoes in the news. But this Monday, a Sherman, Texas self storage facility was hit by a different, but potentially just as devastating, kind of wind that can also come from a severe thunderstorm — a microburst, which is a kind of downdraft. A-American Self-Storage lost the top layer of the roof off one of its five rows of self storage units to high winds from a microburst. Fortunately, A-American’s roof is well made. The lower layers of the roof held steady, and tenants later reported that only a few light sprinkles of water, at worst, were able to penetrate the damaged roof during the remainder of the storm.
Unlike a tornado, microbursts do not rotate. Microburst winds burst straight down out of the clouds. They are like other downdrafts that are common in thunderstorms, but much stronger and faster. As microburst gusts of wind hit the ground, they curl up, continuing to accelerate.
To be classified as a microburst, a strong downdraft of wind must cover an area that is smaller than 2.5 miles in diameter. Microbursts are not common, but do occur fairly regularly. A microburst also hit Kansas City earlier this month, knocking down trees that were up to 15 feet tall and about half a foot in diameter, according to the Kansas City Star. The winds in that microburst were estimated to be up to 60 miles per hour — almost hurricane strength, but not nearly as strong as tornado winds.
The storm ripped through Sherman in a matter of seconds, but it left behind a swathe of destruction, knocking down a radio tower and numerous power lines. Several power lines had to be replaced.
“I got a call from the business down the street saying that my roof was flapping in the wind,” Steve McGaughy, A-American’s manager, told KTEN News on Monday. “After the rain stopped…I came down to see what my roof looked like, this is what I saw.”
In a phone interview today, McGaughy explained that the storm took the slanted metal roof off one row of units and threw it down into the two lanes that are normally available for tenants to use in driving up to their units. “It looked like a 12-foot ball of aluminum,” he said. McGaughy said that although he has managed the Sherman facility for five years, and worked at an Oklahoma City storage center for eight years before that, “I never saw anything like this before in my life.”
In addition to balling up A-American’s roof, the microburst picked up a shopping cart and deposited it on the roof of a Sears mall next door.
A-American’s roofs, luckily, have three layers. McGaughy explained that the bottom layer is made of sheet metal and runs east-west. On top of that lies a middle layer, which combines a wood with a layer of asphalt, similar to the roofs on many high schools. The top layer, the layer that was pulled off by the microburst, is oriented north-south, and is slanted to let water run off during storms. The three layers and the alternating directions of the layers provide a very secure environment for anything being stored below. Tenants at A-American confirmed that their belongings were in good condition with no damage. At most, a few drops of rain were able to penetrate the roof in some spots.
McGaughy, Steve, manager, A-American Self Storage. Telephone interview. Aug. 25, 2010.