NOAA National Severe Storms Laboratory
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THUNDERSTORM FAQs

A derecho is a fast-moving windstorm that is made up of thunderstorms that repeatedly develop along the leading edge. These lines of storms can move very quickly and produce widespread straight-line winds over long periods of time. Derechos can move anywhere from 35-70 mph and last 8 hours or more. Most derechos that produce severe weather move at speeds greater than 50 mph. Warm season events probably move a little slower than cold season events.

Most thunderstorms have hail, but not all thunderstorms produce hail at the ground. Temperatures at the upper levels of a thunderstorm are well below freezing, allowing for the development of hail, but sometimes it melts before reaching the surface of the earth.

Thunderstorm Damage and Impacts

What kinds of damage can they cause?

Many hazardous weather events are associated with thunderstorms. Lightning is responsible for many fires around the world each year, as well as causing deaths when people are struck. Under the right conditions, rainfall from thunderstorms causes flash flooding, which can change small creeks into raging torrents in a matter of minutes, washing away large boulders and most man-made structures. Hail up to the size of softballs damages cars and windows, and kills wildlife caught out in the open. Strong (up to more than 120 mph) straight-line winds associated with thunderstorms knock down trees and power lines. Tornadoes (with winds up to about 300 mph) can destroy all but the best-built man-made structures.

From wreaking havoc on airline schedules to threatening outdoor sporting events, thunderstorms have a big effect on our society.

HOW DOES NSSL CONTRIBUTE?

Promoting research to understand, forecast, and warn of thunderstorms is a significant part of NSSL's role. NSSL scientists have studied the impacts of severe weather on the public and industry, including identifying the effects of the weather, measuring the impacts of forecasts, and providing information that can help inform policy makers in their decision-making processes.

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