NORMAN — Meteorologists know Friday's tornado in the El Reno area was an EF5.
And based on records, they believe it is the widest recorded in the United States.
But there's something they don't want to think about.
“The impacts were horrible of what happened, where it hit and what happened to people and structures,” meteorologist Rick Smith said Tuesday. “We are certainly not minimizing that at all, not at all. But had it gone through the very densely populated areas, this would have been ... I don't even want to imagine what it would have been.”
In the rare category of EF5 tornadoes, the one on Friday in the El Reno area was “super rare,” Smith said.
The National Weather Service's Norman Forecast Office, where Smith works, had rated the storm as an EF3 based on structure damage. Meteorologists updated the estimate Tuesday, determining it was an EF5, the strongest classification for a tornado. It was 2.6 miles wide at its widest point and tracked across 16.2 miles. The storm had wind speeds greater than 295 mph. That 2.6-mile tornado path width is believed to be the widest on record in the United States, according to the Weather Service.
The increase to EF5
The increase in rating came from a study of velocities from the University of Oklahoma's RaXPol radar and the Doppler on Wheels Radars from the Center for Severe Weather Research. The width of the tornado was measured by the mobile radar data to be 2.6 miles after the tornado passed east of U.S. 81 south of El Reno.
Damage indicators were sparse because the tornado struck mostly in rural areas of Canadian County, Smith said.
“That led to the difficulty in determining maximum intensity and maximum width of the tornado based on the ground survey,” he said.
An EF5 tornado has wind speeds of more than 200 mph. Smith said the mobile Doppler radar information showed them this tornado “definitely had well over 250 mph wind speeds.” It also showed a conservative estimate of the width to be 2.6 miles.
“In the rare EF5 category, this is in the super-rare category because we don't deal with things like this, this often,” Smith said. “These were significant findings thanks to our partners here in the research community and at the University of Oklahoma.
“It's rare to get a mile-wide tornado, but this is as if you put two of the Moore May 20 tornadoes side-by-side. That's exceptionally rare to have a tornado that wide. It's never happened before in the United States, as far as we know.”
David Andra, meteorologist in charge with the National Weather Service in Norman, said it was rare for its unusual width and more.
“It also had a very chaotic movement, moving several different directions over the course of its life that made it difficult to predict where it was heading next,” Andra said. “And if you're in the path, it made it difficult to get out of the way.”
In 108 years, there have now been 14 F5/EF5 tornadoes recorded in Oklahoma, according to National Weather Service records.
Since 1999, Oklahoma has had an F5 and three EF5s. Andra was asked why he thinks there have been this many in recent years.
“There's a lot of variability in the natural atmosphere year-to-year,” he said. “We went through many years especially, I can recall, back in the '80s with not too much in the way of violent tornadoes.”
Another factor is that weather experts are measuring the tornadoes better than ever before with some of the truck-mounted radars, he said.
“So we see things now that we didn't see before,” Andra said. “You may recall, the damage alone would have suggested this was an EF3 tornado.
“We may find that stronger tornadoes maybe occur more frequently if we start to make more and more measurements with these highly sensitive ... radars.”
More on the findings
The El Reno tornado began at 6:03 p.m. and ended at 6:43 p.m.
During Friday's storm, the University of Oklahoma RaXPol radar measured winds greater than 295 mph at several times and locations within 500 feet of the ground along the south side of subvortices on the south side of the tornado.
A subvortex is a smaller tornado, although not necessarily a weak one, embedded in an overall large tornado circulation, Andra said.
“These intense subvortices remained over open fields and did not directly affect structures,” Smith said. The two most intense subvortices with the highest velocities occurred north and east of the intersection of 10th Street and Radio Road, about 3 miles southeast of El Reno.
When asked what would have happened if these had hit structures, Smith said, “Going along the ground as fast as these were and with rotational wind speeds as fast as they were, I would have to imagine any house would have been completely swept clean on the foundation. That's just my speculation.”
The previous national record for the width of a tornado was 2.5 miles, set on May 22, 2004, in Hallam, Neb., according to the Weather Service.
“Considering that the United States really holds the records when it comes to tornadoes, I would have to say by extension if it's the widest in the U.S., it's probably the widest elsewhere, as well,” Andra said.
Smith was asked if the El Reno tornado was worse or stronger than the F5 central Oklahoma tornado on May 3, 1999.
“That remains to be seen; we still have analysis of data to do and it depends on your definition of worse or stronger,” Smith said. “It's certainly wider, but that's more of a research question that we get into details on later on.”
Andra said the weather conditions on Friday “had a lot of potential energy in the atmosphere that could be released when thunderstorms developed.” That, coupled with some wind shear that strengthened during the afternoon, created a situation where thunderstorms that produce tornadoes could develop.
“I don't think we understand,” Andra said, “all of the details that went into why this particular storm did all the things that it did. It was a very powerful, complicated storm.”