National Weather Service has confirmed 16 tornadoes in May 12 derecho; total could still grow

Elisa Sand
Aberdeen News

A May 12 storm system that left a swath of destruction in eastern South Dakota and just into Minnesota contained at least 16 tornadoes.

That's according to the National Weather Service office in Aberdeen, where damage reports continue to be evaluated.

Seven tornadoes were confirmed in the days after the derecho, but the number continued to climb as of Monday afternoon.

The storm system had one of the highest number of wind reports of at least 75 mph that NWS has tracked.

According to data collected by the Storm Prediction Center, 64 wind gusts of at least 75 mph were recorded during a December 2021 derecho that rolled through the Central Plains to the upper Mississippi Valley. There were also 64 such gusts in the May 12 system, said Kelly Serr, NWS warning coordinator meteorologist in Aberdeen, 55 of which were reported shortly after the storm.

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Serr said that typically a storm investigation is wrapped soon after the system passes. She hasn't been a part of an investigation that has lasted this long, and the number of confirmed tornadoes could still increase, she said.

The system is defined as a derecho because of wind speeds that ranged from 60 mph to more than 100 mph and tracked over a 240-mile area. The fast-moving storm traveled north-northeast at 50 to more than 70 mph. As it did, Serr said, it hit a warm front between Brookings and Watertown. That warm front, she said, is what created a better environment for tornadoes.

Data collected so far shows that the tornadoes were brief, averaging just less than two minutes in length. The longest was five minutes, and four were less than a minute.

While storms like this are rare, Serr said, they're not unheard of. South Dakota has experienced derechos in the past. Western South Dakota can see one every four years or so, on average, and the region that includes eastern South Dakota and parts of Minnesota, Iowa and Nebraska might have a derecho every two years.

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What set the May 12 storm apart is the speed at which it moved, which hit 80 mph, she said.

The tornado that hit Castlewood was one of three EF-2 tornadoes, with winds ranging from 111 to 135 mph. The others were 1 mile south of Gary and 3 miles east-southeast of Estelline. Of those three, the tornado south of Gary clocked the strongest winds at 135 mph.

Man recovering from heart surgery injured as refrigerator falls into basement

The Gary tornado removed multiple exterior walls of a home, according to NWS reports. Serr said the homeowner, who was recovering from open-heart surgery, took shelter in the basement and saw his dog get swept away in the storm.

"He thought for sure his dog was a goner," Serr said.

But the dog was found a mile away at a neighbor's and only needed some stitches.

Grain bin damage from a May 12 tornado near Dumont.

While the man was in his basement, the tornado toppled his refrigerator, which fell through to the basement. That man was injured and later rescued by firefighters after a neighbor stopped by to help.

Of the remaining tornadoes, nine were EF-1 with wind speeds of 86 to 110 mph, and four were EF-0 with wind speeds of 65 to 85 miles per hour.

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"We’re doing our best to document all this," Serr said, calling the task monumental. "I don’t feel like we’ll ever capture it all."

Here's a little about each of the 16 tornadoes that were confirmed as of Monday afternoon.

Hamlin County, Castlewood

  • Tornado rating: EF-2
  • Peak wind speed: 120 mph
  • Duration: 5:45-5:49 p.m.
  • Storm path: 1.97 miles long, 80 yards wide
  • Injuries: One
  • What happened: The funnel cloud developed at the southern edge of Castlewood with the majority of the damage between Third Avenue and Fourth Avenue.  Multiple buildings were destroyed or damaged, including a funeral home visitor center on Market Street. The school and gymnasium were also damaged and the bus shed destroyed.

Deuel County, south of Gary

  • Tornado rating: EF-2
  • Peak wind speed: 135 mph
  • Duration: 5:58-6 p.m.
  • Storm path: 0.43 miles long, 60 yards wide
  • Injuries: One
  • What happened: A farm 1 mile south of Gary sustained significant damage. Most of the external walls and roof were removed from the home. The nearby garage was also blown off its foundation. A semi to the north was also turned 180 degrees and flipped.

Codington County, northwest of Rauville

  • Tornado rating: EF-1
  • Peak wind speed: 110 mph
  • Duration: 6:02-6:03 p.m.
  • Storm path: 0.2 miles long, 50 yards wide
  • Injuries: None
  • What happened: Approximately 4 miles north of Lake Kampeska, a tornado hit the northeast side of a house and removed the garage and part of the roof. An outbuilding to the north was also destroyed.

Traverse County, east of Dumont, Minn.

  • Tornado rating: EF-1
  • Peak wind speed: 100 mph
  • Duration: 6:51-6:54 p.m.
  • Storm path: 3.34 miles long, 10 yards wide
  • Injuries: None
  • What happened: Tornado developed 6 miles east of Dumont and headed northeast damaging an outbuilding and several large grain bins.

Dumont is east of Sisseton, just across the Minnesota state line.

Traverse County, southwest of Norcross, Minn.

  • Tornado rating: EF-0
  • Peak wind speed: 80 mph
  • Duration: 6:58-7:03 p.m.
  • Storm path: 5.67 miles long, 10 yards wide.
  • Injuries: None
  • What happened: Tornado developed 11 miles east of Wheaton and hit four farmsteads, damaging homes and outbuildings and a silo.

Norcross is about 24 miles east of Rosholt.

Deuel County, southeast of Tunerville

  • Tornado rating: EF-1
  • Peak wind speed: 100 mph
  • Duration: 6:05-6:07 p.m.
  • Storm path: 0.25 miles long, 50 yards wide.
  • Injuries: None
  • What happened: Tornado touched down on the northeast side of Lake Alice, damaging a hunting lodge property. Half the roof was removed from the lodge, and roof panels were removed from the house. Minutes after a family in a camper took shelter, the camper was picked up and dropped on its roof.

Day County, south of Webster

  • Tornado rating: EF-1
  • Peak wind speed: 100 mph
  • Duration: 6:13-6:14 p.m.
  • Storm path: 0.12 miles long, 35 yards wide.
  • Injuries: None
  • What happened: Tornado formed 7 miles southeast of Webster, pulled the roof off an outbuilding and damaged interior walls. A calving shed, animal trailer and metal windmill were also damaged.
Damage to a pole building near Webster after a tornado near Webster.

Hamlin County, southwest of Thomas

  • Tornado rating: EF-1
  • Peak wind speed: 95 mph
  • Duration: 5:40 p.m.
  • Storm path: 0.54 miles long, 20 yards wide.
  • Injuries: One
  • What happened: Tornado formed 4 miles southwest of Thomas. Residents took shelter under a tractor. Tornado ripped off the roof of a new machine shed and damaged exterior walls. Serr said one of the residents under the tractor ended up with a nail in her arm.

Deuel County, southeast of Estelline

  • Tornado rating: EF-2
  • Peak wind speed: 120 mph
  • Duration: 5:39-5:40 p.m.
  • Storm path: 1.69 miles long, 40 yards wide
  • Injuries: None
  • What happened: Tornado formed 3 miles southeast of Estelline, took the roof off a dairy barn and tipped over a camper and several outbuildings.

Clark County, north of Garden City

  • Tornado rating: EF-1
  • Peak wind speed: 97 mph
  • Duration: 6:02-6:03 p.m.
  • Storm path: 0.49 miles long, 20 yards wide
  • Injuries: None
  • What happened: Tornado formed 3 miles north of Garden City and touched down quickly on a farm, removing the roof and exterior walls of a barn.

Clark County, northwest of Naples

  • Tornado rating: EF-0
  • Peak wind speed: 80 mph
  • Duration: 5:45 p.m.
  • Storm path: 0.32 miles long, 10 yards wide.
  • Injuries: None
  • What happened: Tornado formed 4 miles northwest of Naples and removed half a barn roof.

Clark County, northeast of Raymond

  • Tornado rating: EF-0
  • Peak wind speed: 80 mph
  • Duration: 5:45 p.m.
  • Storm path: 0.016 miles long, 10 yards wide
  • Injuries: None
  • What happened: Tornado observed 5 miles northeast of Raymond with a brief touchdown in a field. No damage.

Deuel County, northwest of Gary

  • Tornado rating: EF-1
  • Peak wind speed: 100 mph
  • Duration: 5:59-6:03 p.m.
  • Storm path: 2.078 miles long, 10 yards wide
  • Injuries: None
  • What happened: A tornado formed 2 miles northwest of Gary and caused damage on two properties. Damage included a barn and horse trailer on one property and a garage lifted off its foundation and overturned on the second property. A second garage and a machine shed were also damaged. A grain bin was ripped off its foundation and blown across 485th Avenue into the neighbor's field.

Grant County, northwest of Nassau, Minn.

  • Tornado rating: EF-1
  • Peak wind speed: 100 mph
  • Duration: 6:15 p.m.
  • Storm path: 0.55 miles long, 20 yards wide
  • Injuries: None
  • What happened: Tornado formed 2 miles northwest of Nassau, Minn. The southwest half of a machine shed was destroyed. Rafters from the machine shed were launched through the walls of a nearby shed. About one-third of a roof was removed on a second building.

Grant County, northeast of Twin Brooks, Minn.

  • Tornado rating: EF-1
  • Peak wind speed: 100 mph
  • Duration: 6:19-6:21 p.m.
  • Storm path: 1.3 miles long, 10 yards wide
  • Injuries: None
  • What happened: Several buildings were damaged or destroyed on a farm about 1 mile northeast of Twin Brooks. Damage included a calf shed that was picked up, carried over the shelter belt and then pushed up against the barn; a stave silo that was shifted on its foundation and severe damage to a pole barn. A wood grain bin was moved off its foundation and pushed about 300 feet to the north, and two empty grain bins were destroyed. One of the grain bins and a trailer ended up in a creek. 

Roberts County, south of New Effington

  • Tornado rating: EF-0
  • Peak wind speed: 80 mph
  • Duration: 6:52-6:53 p.m.
  • Storm path: 0.32 miles long, 10 yards wide
  • Injuries: None
  • What happened: Witnesses reported seeing a brief tornado touchdown 5 miles south of New Effington. No damage reported.