NORMAN — The devastation of an EF5 tornado can be mind boggling.
But the occurrence of such can be summed up easily: Rare.
Monday marked only the 13th time in 108 years that an F5, before 2007, or EF5 tornado has been recorded in Oklahoma, according to the National Weather Service, Norman Forecast Office.
Doug Speheger, a forecaster in that office, noted that “despite what it seems like,” conditions to get tornadoes are uncommon. While there are some long-term records, the official tornadoes statistics date to 1950, he said.
In that data, Oklahoma averages 55 tornadoes a year. And although they are possible in any month, May leads with an average of 21, with April at 12.
“So there are only a handful of days where the weather conditions are correct usually for any tornado,” he said. “So it's very rare. It's rare to get the atmosphere unstable and with a high enough wind shear to support an EF5 tornado at all.”
The Newcastle/Moore, south Oklahoma City tornado had a track of 17 miles and packed peak winds estimated at 200 to 210 mph, according to the damage at Briarwood Elementary. And that is part of it. The structural damage factors heavily in the EF rating.
“On Monday, the dryline was set up just west of Newcastle,” Speheger said. “So you had this air converging at the dryline, it helped form the storm west of Newcastle, which then continued to intensify because of the instability and wind shear into what became that tornado.”
Nationally, the National Weather Service records since 1950 show Monday's massive tornado as the 59th F5/EF5 in the U.S.
The last F5 tornado recorded in the nation was that of May 3, 1999, which included areas such as Bridge Creek and Moore. The Enhanced Fujita scale was implemented early in 2007. And then about 9:30 p.m. May 4, 2007, an EF5 struck Greensburg, Kan.
Steve Hewitt, now the city manager in Clinton in western Oklahoma, was the Greensburg city administrator at the time.
“It's like a bomb basically goes off,” Hewitt said. “You see these buildings that have been downtown on a main street for over 100 years that are made really strong, they're 18 inches thick of concrete and brick and they become rubble. They had stood the test of time, but within a matter of minutes there was nothing.”
Hewitt and his family sought shelter in their basement. After the tornado passed, he walked up the basement stairs and looked straight up to see nothing but the night sky.
“A bomb went off, and there's no salvaging anything,” he said. “There's nothing to repair.”
Rick Smith, of the National Weather Service in Norman, said the thing about EF5s that continues to amaze him is the total destruction.
“When you can't find recognizable pieces of a house, when you can't tell the make and model of a car,” Smith said, “you just have to think about the energy and the violence that it takes to do that. You can't put your arms around it.”