Saturday tornadoes confirmed; severe risk returns
Severe weather is expected again in Oklahoma this week after meteorologists confirmed tornadoes hit central parts of the state Saturday.
Survey teams with the National Weather Service in Norman assessed damage left behind Saturday night by severe thunderstorms near Tuttle and Harrah, rating them as “weak” tornadoes on the Enhanced Fujita scale.
“At a point 8 miles west of Harrah, we’ve got evidence of EF1 damage, based on what we’ve seen so far,” said Forrest Mitchell, observations program leader at the National Weather Service in Norman. “Near Tuttle, it’s EF0, and fortunately mainly in open country.”
Meteorologists also were conducting surveys Monday in Lawton and Pauls Valley. The cause of damage in Lawton was dismissed as heavy straight-line winds, but “complicated” preliminary data suggested a weak tornado also might have briefly touched down in Pauls Valley. EF1 tornadoes are characterized by wind speeds between 86 and 110 mph, which can damage roofs, cause doors and windows of structures to break and mobile homes to overturn.
On the other hand, EF0 tornadoes can be challenging for meteorologists to determine, but Mitchell said the main difference between them and merely straight-line winds is the debris pattern they leave behind.
“The damage on the ground, if you look at it from an aerial view, typically has a concentrated, cyclonic swirl to how the debris is oriented,” Mitchell said. “For straight-line winds, the direction that the debris is laying is fairly uniform.”
Mitchell said survey teams largely rely on social media postings from residents and broadcast coverage of severe weather to gain a sense if certain locations need to be evaluated further.
“It’s not like we go out there with a lot of photographers, take a bunch of pictures and come back with them to review,” Mitchell said. “We just go there and take a closer look at the details of the damage and ask ourselves, ‘How strong of a wind would be needed for this particular damage?’”
Severe storms and the risk of flashflooding moved out of Oklahoma and into Texas Sunday night, but meteorologists expected the risk to return later in the week. Another storm system was projected to move into the central U.S. mid-week, with chances for scattered showers in Oklahoma as early as Thursday. The risk of severe thunderstorms across Oklahoma goes up Friday, with increased humidity and southerly winds alongside a drop in temperatures. This unstable climate will contrast with a layer of warm air, often called a “cap,” forming a few thousand feet above the ground and potentially keeping humid air from ascending into the atmosphere and creating heavy storms.
“This is a common challenge that forecasters face with springtime weather systems,” Mitchell said. “Which is going to be stronger: The upward lift from the main storm system, or the strength of the ‘cap’ that’s keeping that relative humidity and unstable air closer to the ground?”
While the chances of severe rain and tornadic activity in late April concerned Mitchell, he also pointed out an ongoing issue – that western Oklahoma hadn’t been receiving enough rain.
“With these increased winds that are coming up and the warmer temperatures, the fire danger is going to become extreme Friday,” he said. “We’re talking about sustained winds of 25 mph, with gusts up to 45, and relative humidity in western Oklahoma below 15%.”
Western Oklahoma has been experiencing drastic drought conditions since late 2021, and portions of the Oklahoma Panhandle have fought widespread wildfires in recent months.
“Especially from Wednesday through Friday, residents in western Oklahoma need to also be alert to the possibility of critical fire weather, with the peak on Friday,” Mitchell said.
Another storm system was projected to move into the central US mid-week, with chances for scattered showers in Oklahoma as early as Thursday.