SOUTH DAKOTA - What constitutes a severe thunderstorm and what makes it different from any other storm. The individuals with the National Weather Service monitor weather conditions across the country as well as thunderstorms. When a thunderstorm means specific criteria, the local weather service will issue a Severe Thunderstorm Warning to alert the public about the pending danger, but what makes this storm severe?
A thunderstorm will be classified as a severe thunderstorm when it is capable of producing hail one inch (2.5 cm) in diameter or larger and/or has winds of 58mph or higher. Back in 2010, the weather service changed its criteria for the size of hail from 0.75 inches to one inch. The reason for the change came after recent studies showed that significant damage was not occurring until the hail size reached one inch or the size of quarters.
Besides the hail, winds of 58mph or higher meet the requirements for severe thunderstorms. Many of us in South Dakota know the winds blow a lot, and you may think 58mph winds are harmless, but straight-line winds are much different then winds from a breezy day.
Straight-line winds cause more widespread damage than tornadoes and can be found along a gust front of a thunderstorm or with a downburst of a storm.
Straight-line winds or large hail, both elements can cause injuries or do significant damage to property. During a Severe Thunderstorm Warning, take shelter and stay away from windows.