An ultra-rare backward-spinning tornado was spawned Tuesday (April 30) from a powerful supercell thunderstorm that formed over the Oklahoma-Texas border.

There have been dozens of tornadoes sighted across the Plains and Midwest over the past week in a relentless severe weather pattern, but one tornado in particular has the meteorology community buzzing.

In the Northern Hemisphere, the vast majority of tornadoes spin counterclockwise. But in rare cases—just 1 to 2 percent of the time—they rotate the “wrong” way, moving clockwise instead. That’s exactly what happened this week when powerful thunderstorms raged across southwestern Oklahoma.

Two such instances happened on April 30, when a supercell southwest of Oklahoma City produced a tornado whose track looped around on itself, and then spawned an anticyclonic tornado with winds spinning clockwise.

Storms bring low tornado risk to Oklahoma on Thursday