rare tornado
© Becky Bates /facebook
A tornado that touched down northeast of Estelline, South Dakota, Saturday evening was rare because it was rotating clockwise, the opposite of most twisters in the Northern Hemisphere.

Radar imagery indicated the tornado was spinning anticyclonically, which is a meteorological term for clockwise. In the Northern Hemisphere, high-pressure systems spin anticyclonically, while low-pressure systems rotate cyclonically, or counterclockwise.

The majority of tornadoes spin counterclockwise in the Northern Hemisphere, similar to larger-scale low-pressure systems, which produce clouds and precipitation.

In fact, estimates indicate that about 1% of tornadoes in the Northern Hemisphere rotate clockwise, like the one near Estelline on Saturday evening, according to the National Weather Service in Aberdeen, South Dakota.

This rare tornado was on the ground for about 45 seconds and was rated EF0 on the Enhanced Fujita scale by the NWS. It was the first tornado to touch down in South Dakota so far this year, according to NOAA's Storm Prediction Center.

The twister's peak winds were estimated at 75 mph. Seven trees were knocked down at a farmstead along its 0.1-mile-long, 10-yard-wide path.

If it weren't for the clockwise spin, this tornado wouldn't have been very newsworthy, but that rare occurrence is news in itself.