Since 2004, the deadly tornado that ground through Hallam, Neb., was the widest tornado ever recorded.
That changed Friday when another devastating tornado churned through a largely rural area outside Oklahoma City, crossing Interstate 40. The tornado claimed at least seven lives, including three veteran storm-chasers.
A number of other people drowned in the flooding that accompanied the storm.
The U.S. Storm Prediction Center said Tuesday that the El Reno tornado, as it is known, was determined to be wider than the Hallam tornado.
At its widest, the El Reno tornado was measured at least 2.6 miles, compared with the 2.5-mile wide path in Hallam, said Rick Smith, warning coordination meteorologist with the National Weather Service in Norman, Okla.
“Not only was this an historic event for Oklahoma, it is an historic event for the U.S. as well,” Smith said.
The storm center also upgraded the El Reno tornado from a rating of EF3 to EF5, the strongest on the Enhanced Fujita scale of storm intensity.
Winds in an EF5 tornado are estimated to be in excess of 200 mph, while winds in an EF3 would likely range between 136 and 165 mph.
Smith said a number of skilled weather researchers with sophisticated equipment were monitoring the El Reno tornado. They discovered that at least six small tightly wound twisters were embedded in the larger tornado. Some of these subvortices were traveling as fast as 185 mph and some were twisting at speeds in excess of 295 mph, he said.
“Mind-boggling,” Smith said.
The state of Oklahoma was blessed that the El Reno tornado occurred in a relatively unpopulated area, Smith said.
“This was an exceptionally powerful storm,” he said. “The impacts were horrible. We were so fortunate that this did not impact a densely populated area. I don't want to imagine what that would have been like.”
The Hallam tornado of May 22, 2004, claimed one life and damaged or destroyed most of the town. Nearly 40 people were reported injured.
The ability to measure the damage path near El Reno was limited, even more so than in Hallam, by the relatively sparse countryside. With few buildings and trees to examine for storm damage, it was hard for experts to say how wide, long or powerful the tornado was.
However, researchers driving sophisticated mobile radar near the tornado were able to record wind speeds that weren't immediately obvious from the damage trail, Smith said.
Smith said he's confident that the true width of the El Reno tornado was greater than 2.6 miles.
The El Reno tornado was on the ground for 16.2 miles and about 40 minutes during the evening rush hour on I-40. As with any tornado, the power of this one varied as it traveled.
Tornado experts have changed the way they rank tornadoes since Hallam occurred, so it's not possible to directly compare the two in terms of power.
The Hallam tornado was rated then as an F4 on the original Fujita tornado sale of F0 to F5, which meant its wind speeds were estimated between 207 and 260 mph.
As was the case with El Reno, the Hallam tornado was so wide that many people didn't realize that was what they were seeing.
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