National Weather Service rolls out new warnings for severe thunderstorms

For years, tornadoes, powerful flash floods and snow squalls have triggered emergency warning alerts from the National Weather Service on cellphones within the danger area.

Beginning Monday, destructive thunderstorms — such as the hurricane-like derecho that ripped across Iowa last summer — will be added to those automatic alerts.

“The overall goal is getting out information in a way and in a format that is going to get folks’ attention and spur them to take action during dangerous conditions and get themselves into shelter,” said Rich Kinney, warning coordination meteorologist in the National Weather Service’s Quad Cities office.

Before this latest change, the weather service issued wireless emergency alerts on cellphones in areas that were under tornado, high-impact flash flood and snow squall warnings. Thunderstorm warnings are the latest addition, Kinney said.

“This is something we’ve been evolving toward … as cellphone technology and capability has evolved,” he said. “It was really kind of a no-brainer to take the next step and add (severe thunderstorms) to the wireless capability.”

It won’t be just any thunderstorm warning that triggers a wireless alert, however. Kinney said the National Weather Service also is changing how it classifies thunderstorms.

The agency previously had a designation for baseline thunderstorms — those with 1-inch hail and/or 58 mph winds — but is adding two new damage threat categories:

• Storms with a considerable damage threat could have at least golf ball-sized hail and/or winds reaching 70 mph.

• Storms with a destructive damage threat could have baseball-sized hail and/or 80 mph winds. The Aug. 10, 2020, derecho would have fallen under the destructive category.

Storms with the destructive tag will automatically activate a wireless emergency alert while storms with the baseline or considerable damage threat tags will not, Kinney said.

“That means this is really one you should pay attention to and you need to get to shelter as quickly as possible,” Kinney said of the destructive storms.

While less powerful storms won’t trigger a wireless alert, Kinney noted that in many areas — including Cedar Rapids — storms with winds reaching 70 mph will activate outdoor warning sirens.

Kinney said the updated storm warning system was in the works prior to the derecho and was not created in response to the devastating storm.

“It takes some time,” he said. “That whole process takes some time and you want to do it right.”

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