SIOUX FALLS, S.D. (KELO) — Twenty-five years ago today a devastating tornado ravaged the small town of Spencer, South Dakota. The F4 tornado was responsible for 6 deaths, injuries to more than 100 of the 320 residents of the town, and damage estimated at $18 million.
The weather on May 30, 1998, was different than what we had this May 30th. At the surface, it was warm and humid as dew point temperatures reached the 60s in southeast South Dakota. An approaching cold front and dry line supplied great lift in the atmosphere to get storm development.
But the main difference was we had a lot more going on in the upper layers of the atmosphere.
Most importantly, in 1998 we had a difference in wind direction and speed as you move up in the atmosphere, this is known as wind shear.
As a result, horizontal rotation developed. With strong lift into the storm, it flips the rotation vertically resulting in a tornado.
Wind speeds with the tornado were estimated between 207 and 260 mph. It’s interesting to know, those wind speeds were supported by the National Severe Storms Laboratory’s portable Doppler radar that was on location during the tornado.
