Extremely Rare Tornado Spinning in Opposite Direction Hits Oklahoma; What Causes Anticyclonic Windstorms?

The Southern Plains of the U.S. are currently in the midst of "tornado season." This year's peak of violent windstorms has brought one of the most strange twister types.

A Unique Kind of Tornado

On April 30, a rare tornado was seen on radar in southern Oklahoma. During an unusual night of weather, strong storms led to hazardous tornadoes, and Tillman County experienced several of them, which exhibited strange behavior.

Two of these tornadoes showed unexpected movements. One powerful column of air rotated back and crossed its previous path again. Meanwhile, the other unusual tornado circled in what is typically considered the wrong direction.

According to meteorologist Rick Smith from the National Weather Service in Norman, Oklahoma, this event is not something that happens every day. What makes it more unusual is that both of these odd twisters came from a single powerful thunderstorm.

What caused this weird weather event? Scientists discovered that a supercell thunderstorm developed close to the Oklahoma-Texas border and traveled eastward. The thunderstorm created a large and extremely dangerous tornado that formed north of Loveland, Oklahoma.

As showcased by radar images, this tornado headed to the east before considerably slowing down. Then, it turned north and west and finally looped over a location it had previously hit. Storms generally move from west to east, but powerful ones can sometimes return to the west as they start to lose strength. Another uncommon feature of this event is that the column of air completed an entire loop back over its path.

According to Smith, it is not common to witness nearly stationary tornadoes since they almost always go wherever the supercell thunderstorm goes. However, the storms on April 30 were barely moving, creating an environment where a tornado could develop, stroll around, and redevelop.

This particular tornado not only churned in the wrong direction while moving forward. It also resulted in tell-tale damage signatures on radar imagery, indicating that it lifted debris thousands of feet into the air. Fortunately, the violent twisters unfolded over a sparsely populated area, so there were no reported cases of structural damage, injuries, or deaths.

What is an Anticyclonic Tornado?

The rotation of the Earth affects weather patterns and ocean currents. Since our planet rotates on its axis, circulating air is deflected in one direction and appears to move at a curve. This phenomenon is called the Coriolis Effect, a force that causes an apparent deflection of the path of an object that moves within a rotating coordinate system.

In the Northern Hemisphere, tornadoes typically spin counterclockwise or cyclonically. On the other hand, those found in the Southern Hemisphere rotate clockwise. These patterns are not followed for anticyclonic tornadoes, so they spin clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

According to the National Weather Service, only about one percent of tornadoes are believed to be anticyclonic. Most anticyclonic tornadoes are weak and short-lived. They are formed from a different process, either companion tornadoes or nonmesocyclonic tornadoes.