The derecho's shelf cloud as seen looking west of Clark at 541pm. Multiple billboards destroyed on I29 southeast of Watertown. Photo courtesy of Dillon Vogtĭamage west of Summit. Series of photos of the Castlewood tornado, courtesy of Brittany Davis Photo courtesy of Ben PennerĬamper tipped at the Lake Traverse Resort. One of several uprooted trees in Big Stone City. Photo courtesy of Aaron Newnsĭamage in Watertown. The dust seen here was blown in from the drought areas of southeastern South Dakota and northeastern Nebraska. Near Astoria at 5:30pm, courtesy of Kyle Coners with the Astoria Fire Department. Time lapse of the storm and dust as it approaches Sioux Falls, as seen from the airport. You are part of the process that aims to save life and property. Thank you to everyone who provided ground-truth during and after the storm. Video of the Castlewood tornado, courtesy of Chris Schmidt.
The National Centers for Environmental Information, NCEI, determined this to be a billion-dollar disaster event. A Presidential Disaster Declaration was later approved for South Dakota.
On May 13th, South Dakota Governor Kristi Noem ordered a State of Emergency for storm response and ordered state personnel and resources to communities impacted by the damaging storms. Widespread impacts resulted from this storm, including uprooted or snapped trees, significant property damage, power outages, tipped high-profile vehicles, as well as injuries and a couple fatalities across the region. At this location wind speeds are estimated at 135 mph, which ranks it as a high end EF2 tornado. Another farmstead south of Gary, SD was also devastated by a tornado. Many significantly damaged or destroyed structures resulted. An EF2 tornado, with wind speeds up to 120 mph passed through the town of Castlewood, SD. Some of the worst damage occurred in Hamlin and Deuel counties. Significant blowing dust was also reported, especially across southeastern South Dakota. Additionally, 34 tornadoes have been confirmed: 19 in Minnesota, 13 in South Dakota, and 1 in both North Dakota and Iowa. This is about the same as a category 1 hurricane (74 to 95 mph) and an EF0 to EF1 tornado (65 to 110 mph) over a large area. It raced north-northeastward at 50 to 70+ mph, and produced measured straight-line winds of between at 60 to over 100 mph. A particularly dangerous storm system known as a derecho moved through the Northern Plains during the late afternoon and early evening hours of Thursday, May 12th, including eastern South Dakota and west central Minnesota. Derechos feature unusually widespread wind damage, and this was the most extreme example on record in terms of the number of measured significant wind gusts.