Norman, Oklahoma - The deadly tornado that struck near Oklahoma City late last week had a record-breaking width of 4km and was the second top-of-the-scale EF5 twister to hit the area in less than two weeks, the National Weather Service said on Tuesday.
The weather service initially rated Friday's tornado as an EF3. But the agency upgraded the ranking after surveying damage from the twister, which along with subsequent flooding killed 18 people. The weather service determined that the storm had winds reaching 474km/h.
The update means the Oklahoma City area has seen two of the extremely rare EF5 tornadoes in only 11 days. The other hit on 20 May, killing 24 people and causing widespread damage.
Friday's massive tornado avoided the highly populated areas near and around Oklahoma City, and forecasters said that likely saved lives. When the winds were at their most powerful, no structures were nearby, said chief warning coordination meteorologist Rick Smith with the weather service.
"Any house would have been completely swept clean on the foundation. That's just my speculation," Smith said. "We're looking at extremes ... in the rare EF5 category. This in the super rare category because we don't deal with things like this often."
Three storm chasers died in Friday's storm.
Smith said the storm's wide path, besting a record set in 2004 in Nebraska, would have made the storm hard to recognize up close.
"A two and a half mile wide tornado would not look like a tornado to a lot of people," Smith said.