CHARLOTTE, NC (WBTV) - A new study by the National Weather Service reports that the strong downburst winds observed during severe thunderstorms could be more dangerous in the Carolinas than tornadoes.
Why? Because unlike tornadoes, severe thunderstorms are very frequent and can affect a large area. Tornadoes on the other hand are very localized events, and don't happen that often. While tornadoes require just the right environment to form, all a thunderstorm needs is warm air and moisture.
Downbursts are especially common in the Piedmont. A typical Piedmont county will experience at least one downburst on 4 to 7 days per year. Tornadoes, on average, only occur once every 3 to 5 years in the same county. In addition to warm air and moisture, tornadoes need another ingredient: wind shear. This change in wind speed and direction as you climb higher in the atmosphere is usually not present in the spring and summer months, resulting in relatively few tornadoes.
During the early stages of a thunderstorm, warm air starts to rise due to its low density. As the warm air rises in a moist environment, water droplets form, creating clouds and eventually storms. The air will continue to rise as long as the atmosphere remains unstable, sometimes as high as 50,000 feet upward. These tall storms will produce very heavy rain, which will cause the surrounding air to cool. Just as warm air rises, cool air sinks, and can do so very quickly. The more dense cold air heads downward, then after reaching the surface, fans out. Often moving at a rate of 60 mph or greater. This fast-moving air is referred to as a "downburst."
In extreme cases, downbursts can produce wind gusts of 70 to 90 mph, the strength of a Category 1 hurricane. These strong winds can blow down trees and power lines, and in some cases even flip mobile homes. Over the past 20 years, 7 deaths have been associated with thunderstorm winds in the western Carolinas and northeast Georgia, each fatality the result of a falling tree.
The safest place to be if a Severe Thunderstorm Warning is issued for your area is in an interior room on the lowest level of a well constructed building. If you're in your car or a mobile home, find a sturdier shelter.