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Reviewing Storm Standards

Experiment tests threshold for severe thunderstorm warnings
Friday, May 13, 2005 | 12:00 a.m. CDT; updated 4:12 p.m. CDT, Tuesday, July 22, 2008

Fewer severe thunderstorm warnings and a new definition of severe weather could be the result of a National Weather Service experiment in western Missouri and Kansas.

Currently, the threshold for a severe thunderstorm warning is at least three-quarter-inch hail or winds in excess of 58 mph.

In the experimental area, the weather service is using a standard of 1-inch-diameter hail.

James Kramper of the National Weather Service in St. Louis said the regular warning guidelines were established years ago by the National Weather Service and the U.S. Air Force. This experiment marks the first time the weather service has changed the criteria for severe thunderstorms.

One of the reasons for the experiment is the frequency of severe storm warnings. Some people have come to give them short shrift, said Steve Runnels of the National Weather Service in Springfield.

“Many groups expressed concern over the number of severe thunderstorm warnings, and this tends to lend a lessened response when people hear them,” he said. Runnels said the requirement for hailstones increased to a 1-inch diameter in the experiment area because that is the size at which hail is more apt to damage cars and homes.

“We’re trying to find out if the warning message does carry more value when it’s issued less frequently, and if the emergency community finds it is a prudent move in raising that criteria,” Runnels said.

Runnels said the National Weather Service wants to determine whether residents in the experimental areas would react to the new standards for severe weather. Based on the response, officials might expand the project. If that occurs, Kramper said, the first expansion would probably be regional rather than national.

“Right now, a lot of people in the Midwest would agree we’d want to change it,” Kramper said. “But there are a lot of people in the country who wouldn’t want to because they don’t get hail as often.”

For now, only Kansans and Missourians who live in counties served by National Weather Service offices in Springfield and Kansas City will see a change. Warnings and other advisories for Boone County are issued by the National Weather Service in St. Louis.

“The biggest impact mid-Missourians will see are fewer warnings west of Columbia,” Runnels said.

Boone County has seen 216 severe thunderstorm warnings since 1986, according to recent statistics in the National Weather Service interactive warnings database.

In 2004, 11 severe thunderstorm warnings were issued for Boone County. There have been more than a half-dozen so far this year.

The experiment began in March, and Runnels said any change the experiment brings to the number of severe thunderstorm warnings probably won’t be evident until after July, when thunderstorm activity tends to pick up.

Alerting the public about severe weather is a shared responsibility. The National Weather Service issues storm warnings, but local emergency officials make decisions on whether to sound sirens.

Donna Hargis of the Joint Communications Center in Columbia said there is no rule of thumb for setting off the sirens; whether the sirens go off depends on the circumstances of each storm. Although some people might not take weather warnings and outdoor sirens seriously, she said, these actions are necessary precautions.

“There are always going to be people who disagree with you.” Hargis said. “If you set off the sirens, they might be seeing clear skies, but a couple of miles down the road that might not be the same case. You’re going to have pros and cons as far as what people think.”

Even with the National Weather Service and local emergency officials getting the word out about incoming storms, Kramper said, everyone should take time to turn on the TV, radio or weather radio to learn more about the threat and what precautions should be taken.

“When you hear a warning, it doesn’t mean go blindly into your storm shelter; it is an alert system to tell you to find out what’s happening,” Kramper said. “People want to be spoon-fed, and that’s just not possible.”

Hargis said that when people hear sirens, they should take shelter and seek additional information.

“As far as activating sirens, people should immediately go inside and seek information from local radio stations and TV stations,” she said. “Hopefully, those people should be giving out the information that these people need.”


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