NORMAN — The instability in the atmosphere stirring Friday above central Oklahoma was of rare proportions, a meteorologist said.
There was a mix of incredible amounts of moisture and warm, muggy conditions, said Kevin Brown, a senior forecaster with the National Weather Service, Norman Forecast Office.
A large, slow-moving cluster of supercell thunderstorms moved across central and northern Oklahoma in the late afternoon and evening on Friday resulting in at least five tornadoes. Other storms developed to the west and moved over the same areas as the first storm.
This produced significant flooding in areas including the Oklahoma City metro.
“When the atmosphere becomes very unstable like yesterday,” Brown said Saturday, “then a lot of times when we get storms to develop, it's not just one supercell, it's a huge conglomerate of very intense storms. We had this massive area of severe weather across Canadian and Oklahoma counties.
“And when the atmosphere is that unstable they start to alter the environment around them.”
As a result, storms that developed over southwest Oklahoma dissipated as they approached central Oklahoma, Brown said.
On Saturday, the National Weather Service, Norman sent out three damage survey crews to various parts of the Oklahoma City area.
The first tornado developed around 5:55 p.m. Friday near El Reno. This storm then moved east to southeast into western and central portions of Oklahoma City, producing other tornadoes. The primary tornado that started near El Reno has been given a preliminary rating of EF3 while the other preliminary tornado ratings include two EF1s and two EF0s.
For the EF3, a primary damage indicator during Saturday's survey was a single family dwelling just east of U.S. 81 near El Reno, Brown said. Based on the damage, the peak wind speed was estimated at 156 mph. He said additional EF3 damage was found in other locations both east and west of U.S. 81 near El Reno.
And the floods resulted as four to eight inches of rains fell in areas of the Oklahoma City metro to the Oklahoma/Arkansas state line, Brown said. This occurred primarily in a span of three to four hours.