Why Oklahoma Tornado Supercell Was So Unusual

A deadly tornado ripped across parts of Oklahoma on April 19, leaving at least three people dead and many homes without power.

The outbreak came at the start of Oklahoma's tornado season, which runs from April to June. However, there was something particularly unusual about this tornado.

A severe thunderstorm was first developed over Apache and Chickasha, to the southwest of Oklahoma City, shortly after 5 p.m. local time, the National Weather Service reported. It then began to move northwest, producing "baseball size hail." As it swept over Newcastle, and into Valley Brook, the storm had already turned into a tornado while a second storm followed its path.

Residents of Cole were then warned to take shelter immediately as the NWS warned the tornado was producing a "dangerous situation." As the tornado moved over Cole, it gathered a speed of 30 mph.

Experts have noted that the tornado had a very unusual structure.

Noah Bergren, a meteorologist for WPSD Local 6 in Kentucky said in a tweet that the tornado had an "insane structure."

Videos of the gigantic tornado were also captured by Zachary Hall, a storm chaser, who said in a tweet that it didn't "even seem real."

The tornado was on account of a supercell storm, a rare storm that causes violent weather.

Supercell storms typically last for a long time, circulating from above. The circulation aloft grows in an upwards direction through the storm, and then also downward, towards the floor. While most supercell storms cause violent weather, only around 30 percent actually result in tornadoes, the NWS reported.

But the supercell storm in Oklahoma deviated from what experts usually see.

When a tornado does form, it either moves from west to east or southwest to northeast.

But this tornado took a completely different track, and instead turned north, Fox Weather reported.

The network's senior meteorologist Jordan Overton said in a news report that this is known as a deviant tornado motion.

"This is simply defined as when a tornado takes a completely different track than what we usually see. Deviant tornado motion is when a tornado takes a hard left turn, remains stationary, or rapidly changes directions," Overton said. "These are typically strong tornados and can cause high-end impacts, which is what we saw."

This can result in tornadoes being even more dangerous. Tornadoes are already quite difficult to predict, but this adds another layer as it makes their path a mystery.

Jana Houser, an associate professor of meteorology at Ohio State University and atmospheric scientist specializing in the study of supercells and tornadoes, previously told Newsweek: "Scientists still don't quite understand all of the nuances in figuring this out and differentiating between storms that are occurring in essentially the exact same environment but one produces a tornado and another neighboring storm does not, even when they're separated by distances that are relatively small."

"So it's the part of looking at a storm and figuring out if it's going to produce a tornado in the next 15 minutes that really is challenging!" Houser said.

The Oklahoma tornado also demonstrated the Fujiwhara effect—the phenomenon when storms circle around each other, counter-clockwise. This is something that is usually only seen in hurricanes. However, it does happen with tornadoes in rare instances.

Meteorologist Reed Timmer said on Twitter that the Fujiwhara effect "is more common" than one might expect "but not as persistent and prolific" as this.

These two phenomena can happen occasionally in tornadoes, however, it is uncommon. The fact that both occurred in one tornado is extremely rare.

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