The Coffee County Emergency Management Agency Office received numerous calls asking about the frequent number of warnings issued during storms Saturday, April 24.
Coffee County EMA Director James Brown outlined the reason why. “Each of those calls was a separate ‘Severe Thunderstorm Warning’ and they are meant to warn residents of storms producing harmful wind and hail in their immediate area,” he said.
“The system on Saturday was unusual as it wasn’t our typical squall line that moves in and through the area over a short period of time,” Brown said. “This storm produced many individual cells, each of which were dangerous and capable of producing damaging winds.”
Brown said some of these warnings were also extended or upgraded, meaning that the storm may have strengthened and a new warning was necessary. “For example, one of our severe thunderstorms on Saturday was upgraded from a 60 miles per hour wind threat to a 70 miles per hour wind threat, prompting a new warning for the same storm,” he said. “We keep the public aware of severe thunderstorms because the straight-line winds —micro and macro burst—they produce can be just as destructive as a tornado.”
The National Weather Service considers a thunderstorm “severe” when the storm is capable of producing winds that meet or exceed 58 miles per hour and/or hail of 1 inch or larger and/or a tornado, according to Brown.
Damage from the winds produced by severe thunderstorms account for half of all severe damage reports in the United States and is more common than damage from tornadoes. Wind speeds from thunderstorms can reach 100 miles per hour and can produce a damage path extending for hundreds of miles.
Brown said that some times damage produced by straight-line winds is attributed to tornadoes. “Downbursts or straight line winds are produced by the downward momentum in the downdraft region of a thunderstorm and can cause severe damage in an area up to six miles from the storm. Downbursts are further subdivided into microbursts and macrobursts.
A tornado, on the other hand, is a violently rotating column of air that extends from the base of a thunderstorm to the ground. “The key difference can be summed up in two words —in and out,” Brown said. “When all wind flows into a tornado, debris is often laying at angles due to the curving of the inflow winds. When all wind flows out from a downburst—straight-line winds—debris is often laying in straight lines parallel to the outward wind flow.”
Both can cause significant and extensive wind damage, Brown said. Tornado winds range from 65 to more than 200 miles per hour. Straight-line winds can exceed 100 miles per hour—the equivalent of an EF-2 tornado—and can tear off roofs, knockdown trees, shift foundations and completely destroy mobile homes.
“This is why we think it is best that you get warned with each severe storm cell that approaches your location, even if it is multiple times a day,” Brown said. “It is much better to be prepared then to experience the devastation that could be caused by a severe thunderstorm without warning.”