| Basin: | atl |
| Winds: | 170mph |
| Fujita-Scale: | EF4 |
| Enhanced: | yes |
| Deaths: | 1 |
| Injuries: | 2 |
| Damages: | $1.855 million (2020 USD) |
| Affected: | Grant County &Otter Tail County, Minnesota |
| Season: | tornado outbreaks of 2020 |
On the afternoon of July 8, 2020, a violent and deadly drillbit tornado struck the area between the towns of Ashby and Dalton, Minnesota.[1] [2] [3] The National Weather Service in Grand Forks, North Dakota rated the worst of the damage from the tornado EF4 on the Enhanced Fujita scale.[4] [5] [6] The tornado was also used as the cover for the 2021 disaster film 13 Minutes.
The Ashby–Dalton tornado occurred in an area covered by a severe thunderstorm watch issued by the National Weather Service Storm Prediction Center at 4:10p.m. the day of, which had mooted the risk of "a tornado or two" occurring.[7] The supercell thunderstorm that spawned the tornado developed just before 5:00p.m., and was rotating strongly enough to garner a tornado warning by 5:08p.m. Weather spotters observing the storm passed on information to the local National Weather Service office as a funnel cloud developed and would become the Ashby–Dalton tornado.
The tornado touched down at EF0 to EF1 intensity, approximately 6miles west of Ashby, in Grant County.[1] [2] The tornado initially moved southeast before turning northeast.[8] After traveling 2miles, the tornado intensified to at least EF1 intensity as it entered Otter Tail County, where it turned due north before again turning to the northeast.[1] [8] The tornado briefly skipped over I-94 before touching down on the other side at EF2 intensity.[1] As the tornado crossed County Road 82, it quickly intensified to EF3 strength and reached its maximum width of 650yd.[1] Here, a machine shop was completely destroyed and swept off its foundation, killing one person.[4] The victim, a 30-year-old man, had been taking videos of the tornado on Snapchat as it approached him and his colleague. His colleague sheltered by hanging on to the underside of a tractor in the machine shop, and survived.[9] The National Weather Service rated the damage to the newly built machine shop EF3, with winds estimated to have been between NaNmph.[1] [8] [6] [4]
As the tornado continued northeast, it struck a well-built two-story house on a rural homestead along 120th Street, which was decimated and completely swept off its foundation with debris widely scattered. Two people sheltered in the basement and survived with injuries after the tornado hurled debris, including an entire vehicle, into the suddenly exposed space. Two other vehicles near the house were moved 40yd and 300yd northeast respectively. One lost its engine. Nearby trees were denuded, stubbed, snapped, and lofted long distances.[10] The homestead was judged by the National Weather Service to be the tornado's point of maximum intensity, with estimated wind speeds of at least 170mph and a damage rating of EF4.
As it crossed County Road 117 the tornado produced significant damage to trees and crops, ranging from EF2 to EF3 in intensity. As the tornado began to dissipate, its movement became erratic, turning due north before turning due east and then again turning due north. While dissipating, the tornado likely maintained its strong-to-violent intensity, causing deep ground scouring. The tornado finally dissipated between 145th Street and County Road 12.
In total, the tornado killed one person, injured two others, and caused over $1.8 million (2020 USD) in damage along its 9adj=onNaNadj=on path.[11] [12]
The tornado spawned from a low-precipitation thunderstorm with a high cloud base, making it remarkably visible. Multiple storm chasers captured photographs and footage of the photogenic tornado, which at times dwindled to just 10feet in width. A photograph of the Ashby–Dalton tornado was used in the cover for the 2021 disaster film 13 Minutes.[13] [14]