A severe thunderstorm is capable of producing many types of wind. Sometimes, damaging wind is in the form of a tornado. More often, straight-line winds are the cause of damage in a severe thunderstorm. The graphic below shows how this type of wind is created.
Simply stated, there are two main types of damaging wind, not including tornadoes.
The Microburst
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| A microburst is a downward rush of wind from a thunderstorm. In the Dallas/Fort Worth Metroplex, they are sometimes easy to spot because it looks like the cloud is rushing to the ground. Once the airflow makes contact with the ground, the wind has to go somewhere. Usually it will spread out along the ground in a horizontal motion. That horizontal movement is where we get the term Straight-line wind |
Straight Line Winds
These winds can exceed 100 miles per hour. Looking at the Fujita Scale for tornado intensity, we can see that is in the middle of the range for an F-1 tornado. This wind speed is well past the lower limit of hurricane wind speed and can do things like peel shingles or other surfaces off roofs, push mobile homes off foundations or overturn them, push moving autos off the roadway, and make a good attempt to destroy attached garages.
 Microbursts and the resulting straight-line winds are a damage causing combination. The photo at the left is a picture of a "wet" microburst. Just like a tornado, it may not be possible to see such phenomena until debris, dirt, or water is picked up by the wind. The best lesson to learn is that just because you can't see it doesn't mean it is not there!
Appropriate Response Actions for Straight-Line Winds
Considering the associated wind speeds for this type of phenomenon, personal response actions for this type of storm are going to mimic the actions you should follow in a tornado warning. See the response information listed under tornadoes for more information.
Beyond immediate response considerations, there are a few mitigation steps that might help your family through a straight-line wind event. First, look at the exterior of your home and try to imagine how items in your yard could get tossed around and damage your home. Based on that information, you may want to relocate some items around your home or establish something to secure them in place. Another concern involves the trees are often blown over in a strong wind event. A North Carolina State University study that focuses on tree hazards might offer some assistance for people with large trees in their yard.
Those with an interest in maritime activities, should familiarize themselves with the Beaufort Wind Scale. This scale was developed in the early part of the 19th century to assist mariners with sailing conditions.
The Power of a Microburst
The picture below will show how a powerful microburst event occurs. In August 1985, Delta Flight 191 was approaching the airport from the north when it flew through a strong microburst.
Following their training, the pilots realized that the airplane was in a very hazardous downdraft situation and kept the nose and power high in full expectation of the downdraft immediately in front of them. In this case, the outflow was so strong that it lifted the nose of the airplane so high it was almost in stall. In response, the pilots lowered the nose of the aircraft, as they flew through the downdraft portion of the microburst. Unfortunately, they were never able to keep the plane in the air.
Photographs on this page are courtesy of the National Weather Service. |
