SIOUX FALLS, S.D. (KELO) — An 80 mph straight line wind is powerful, said Mike Gillispie, a meteorologist with the National Weather Service in Sioux Falls.
A storm “doesn’t care if the winds are straight line or rotating. An 80 mph wind is equal to an EF1 tornado,” Gillispie said.
The storms that happened in South Dakota and other parts of the region in southwest Minnesota and northwest Iowa didn’t produce the derecho of May 12, but they did cause damage.
“Once you get to 80 mph plus, that’s when you will see damage to rooftops and buildings…,” Gillispie said.
Numerous trees were uprooted and branches were broken throughout the area of storms this past weekend.
“Those high winds are typically at the front edge of a severe storm,” Gillispie said. “In the middle of the storm or back end, is where you will have 50 to 60 mph winds,”
How Memorial Day storms differed from May 12
The path of the May 12 derecho was wide and long- lasting over a day.
“These (Memorial Day weekend) were more ‘normal’ severe storms, if you’d use normal,” Gillispie said. “They were more isolated. They weren’t as well-developed over a huge, long, line. They weren’t as of big of scale as what you saw with a derecho.”
KELOLAND meteorologist Scot Mundt said the storm period lasted over about 36 hours from Sunday night, May 29, through Monday, May 30, Memorial Day.
“The weekend storms didn’t develop into a derecho for several main reasons,” Mundt said.
The dew points and moisture levels were not as high. “There was not as much energy in the atmosphere,” Mundt said.
On May 12, “we didn’t have as many storms compete for energy,” Mundt said.
Also, it was not as hot. The temperature reached 94 F on May 12. On Memorial Day the temperature didn’t break 80F.
“We didn’t have as much sunshine,” he said.
Mundt described three different main storm time periods. The first was Saturday into early Sunday morning with large hail. Hail the size of baseballs was reported.
The next period was Sunday night into early Monday morning.
“The winds that moved through Sunday until 1 and 2 a.m. Monday’s were high,” Mundt said.
The third period of storms was later Monday into Monday evening.
“(Monday day) they weren’t as organized, they were more isolated…,” Mundt said.
Overall, Gillispie said, the storms moved quickly throughout the state at about 40 to 45 mph.