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Wind
is one of the most powerful forces of nature. Every
year, wind causes more than six billion dollars in damage throughout the
country. The damaging wind comes from hurricanes, tornadoes and severe
thunderstorms. Wind damage is no stranger to the Gulf Coast. To put it
simply, wind is air in motion. Its job is to transfer heat and moisture
around the planet. In the process, it makes things move.
The wind is always blowing several miles above the ground. We notice it more in the afternoon when rising air currents mix the air and transfer the higher wind down to the ground. Wind is most calm at sunrise and then it picks up with the heat of the day. Of course, when a storm moves through the wind increases.
Wind is so much a part of our lives. It cools us down in the summer. It robs us of heat in the winter. Wind can be gentle or it can be deadly and damaging.
Wind Facts:
- Average annual wind in Mobile: 8.8 mph
- Average annual wind in Chicago: 10.4 mph
- Highest hurricane wind: over 190 mph
- Highest tornado wind: over 300 mph
- Highest wind recorded on the Earth's surface: 231 mph on top of Mt. Washington, NH.
When there's a major hurricane, wind damage can far exceed the six billion dollar annual average. Hurricane Isabel, by itself, produced more than half a billion dollars in damage in 2004. Hurricane Andrew in 1992 created more than 25 billion dollars in damage, much of it by wind.
The
potential for damage increases when wind is over 58 mph- that's the threshold
for a severe thunderstorm. It's rare that you can safely experience wind
at this level. So I traveled to Texas A&M University, where they make
their own wind in the Oran Nicks Wind Tunnel. In this research facility
in College Station, scientists test wind speed, airflow, and wind force.
For protection I geared up in goggles, earplugs, and a harness. My harness was secured to a post. Two more restraints provided more safety, for a good reason. The tunnel is a circular tube, large enough to hold a car. Right behind me was an engine with propellers, capable of generating wind of 200mph.
We started with a 10mph wind. While it was loud in the tunnel, you could barely tell the air was moving. We then doubled the wind speed to 20 mph. At that point I could feel the wind. It was hard to hold an umbrella without it turning inside out. We then moved the speed up to 40 mph. That's the strength of a weak tropical storm. I didn't have any problem standing but the umbrella did.
At 40 mph the wind was four times faster than when we started but the force of the wind was 16 times greater. So much of the damage of wind is due to the force, not the speed. Wind blowing directly against a flat surface will have more force than wind blowing on an angle toward a surface. As wind increases, the force increases at a much faster rate. That's why a small increase in hurricane strength can produce a big increase in damage.
Finally we increased to hurricane force- 80 mph. At this speed I could barely stand upright. The force of the wind was then 64 times greater than the force of a 10 mph wind. Not only did the post and tether save me from being knocked to the ground but the force of the wind made it extremely hard to breath. Every time the wind speed doubles, the force increases by four times.
After the wind tunnel experience I can better-relate to damaging wind. The higher the wind, the greater the stress is to any object, building, or roof. We can't reduce the wind but we can reduce the damage to homes and buildings.
If the roof is not securely connected to the walls, high wind can lift it. Have a licensed professional inspect the connection of your roof to the walls. Some older roofs merely sit like a cap on the house, while others may only be fastened in a few spots. The roof needs to be strapped to the walls.
If the roof to wall connection is strong but the house is not bolted or strapped to the foundation, high wind can move the entire house, intact. In new construction make sure walls are bolted to the foundation. For mobile homes make sure the home is strapped and anchored. Even homes that sit on piers or pilings need to be well-anchored.
If you have control on the design of new house construction, choose a structure and roof shape that is more wind resistant, like a hip roof on a lower house.
David
Wiggins is a Certified Inspector, with All Angles home inspection. He says,
the "hip style comes down on all four corners so naturally when the wind
comes in, it has the tendency to go up and over versus a gable style. You
have a flat surface for the wind to push against." David also recommends
that all roofs be reinforced with cross-beams, and end beams if practical.
Once you do as much as you can to strengthen the structure of your house you can't forget flying debris. Beams of wood can penetrate the side of a building if they are moving fast enough, and smaller debris can easily break windows to enter your home in high wind.
Trim tree branches that are weak or dead. Also whenever we are under a watch for severe or tropical weather, carry yard furniture, toys, trash cans, and other loose items inside.
Visit these links for detailed instructions on reinforcing your home from wind.
Federal Alliance for
Safe Homes- FLASH
National
Hurricane Center Wind Safety
Tornado
Wind Safety
Students and teachers may want to build your wind tunnel using these instructions from NASA or these plans from the FAA.
You can also download these PDF files Avoiding
Wind Damage (235kb), and Against
the Wind (225kb).
