Why did Oklahoma get storms Wednesday, but not North Texas? It’s all about the ‘cap’
Storms stayed north of Texas Wednesday because of the “cap,” according to the National Weather Service Fort Worth office.
So, exactly what is it?
“The cap is just a layer of warm air aloft that essentially prevents the air at the surface from lifting,” said Sarah Barnes, meteorologist at the NWS Fort Worth office. “For thunderstorms you need to be able to lift the air in order to get the thunderstorms.”
For example, when water and oil mix together, the latter always rises to the top. That’s what happens with warm and cool air, because warmer air wants to rise because its less dense, Barnes said.
That’s where the cap comes into play. It keeps the cooler air from rising thus suppressing thunderstorms.
The ‘Cap’: How this weather phenomenon occurs
The cap develops frequently overnight when the air near the surface cools and the warmer airs rises to a few thousand feet above the ground, Barnes said.
If there isn’t enough surface heating from the sun or a dry line or cold front, the cap is going to stay where it is. Since there wasn’t much lift yesterday, she said the cap suppressed any thunderstorm chances.
“It was just a little bit too strong, so yeah we ended up not seeing any storms but Oklahoma did,” Barnes said.
How is the “cap” measured?
Weather balloons are used to measure the strength of the cap.
The NWS Fort Worth office released multiple balloons Wednesday to asses how the cap was holding up, Barnes said. By the 3 p.m. balloon, the cap was holding so strong that the meteorologists thought that North Texas wouldn’t see many storms at all.
This story was originally published February 16, 2023 at 12:53 PM.
