| A storm is any disturbed state of the atmosphere, especially affecting the Earth's surface, and strongly implying severe weather. It may be marked by hard wind (a wind storm), thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, hailstorm, etc). Storms are created when a center of low pressure develops, with a system of high pressure surrounding it. This combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. A strict meteorological definition of a storm is a wind measuring 10 or higher on the Beaufort scale, meaning a wind speed of 89 km/h (55 mph) or more; however, popular usage is not so restrictive. |