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Preliminary Storm Summary for May 12, 2022 Derecho

A derecho moved through the Northern Plains during the late afternoon and early evening hours of Thursday, May 12th, including e SD and w central MN. It produced straight-line winds of between at 60 to over 100 mph. Several tornadoes were reported and confirmed. Some of the worst damage occurred in Castlewood, when an EF2 tornado with wind speeds up to 120 mph passed through town. Read More >

Overview

During the evening of June 15, 2019, a brief tornado occurred 5.5 miles to the northeast of Estelline, SD.  The tornado lasted less than a minute (at around 6:05 PM CDT) and knocked down 7 trees at a farmstead.  The tornado was moving in an easterly direction and the tornado tossed tree branches to the south and west from the group of trees that were knocked down.  One of the trees hit the corner of a shed and bent part of the metal overhang on the shed. 

Based off radar data, damage report, and a Facebook video, the tornado that occurred northeast of Estelline appears to be a very rare "anticyclonic" tornado, which means that it was rotating in a clockwise direction. In the Northern Hemisphere, nearly all of the tornadoes that occur rotate in a counter-clockwise ("cyclonic") direction and estimates indicate that maybe only 1% of tornadoes are anticyclonic like the one that occurred on June 15th.

This storm split off from the parent thunderstorm and moved easterly, while the parent storm continued to the southeast. Meteorologists define these types of storms as "left moving" since they move to the left of the storm that they split from.  

Screenshot from Facebook video by Sean and Kathy Lesnar
Screenshot from Facebook video by Sean and Kathy Lesnar
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