Video: The start of the El Reno tornado
The deadly tornado that hit near Oklahoma City last week was wider than Manhattan and the widest on record at a terrifying 2.6 miles (4.2 km) across.
The tornado was the second top-of-the-scale EF5 twister in the area in 11 days the National Weather Service said. Winds inside the tornado nearly reached three hundred miles an hour, just shy of the strongest winds ever measured.
Nineteen people were killed in the storm and subsequent flooding, including three storm chasers. The tornado was originally graded as an EF3 but following a survey of damage and the high-speed winds was upgraded to EF5.
It followed an EF5 tornado on May 20 which hit the suburb of Moore, 25 miles southeast of El Reno, and killed 24 people. The tornado on Friday managed to avoid heavily populated areas, sparing lives
William Hooke, a senior policy fellow of the American Meteorological Society, said the continued growth of cities in tornado-prone areas makes it only a matter of time before another monstrous twister hits a heavily populated area.
"You dodged a bullet," Hooke said. "You lay that path over Oklahoma City, and you have devastation of biblical proportions. It's only a matter of time."
When the winds were at their most powerful Friday, no structures were nearby, said chief warning co-ordination meteorologist Rick Smith with the weather service.
"Any house would have been completely swept clean on the foundation. That's just my speculation," he 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."
Mr Smith said the storm's wide path would have made it hard to recognise up close.
"A two and a half mile wide tornado would not look like a tornado to a lot of people," he said.
- More about: