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John Myers, Forum News Service, Published March 29 2013

NWS expands severe weather warnings

DULUTH – National Weather Service forecasters are working to be more descriptive and detailed when they issue severe storm and tornado warnings starting Monday with a new, three-tier warning system aimed at persuading people to take action based on real risk.

The new “impact-based warnings” will be issued not just for a specific area the storm is approaching but also based on the potential power of the storm and the known level of threat.

Starting Monday, residents of Minnesota, Wisconsin, North Dakota and nine other states will join Kansas and Missouri, where the warnings were tested last year.

• The most-basic warning will be issued when meteorologists “see” a potential tornado-bearing storm on Doppler radar. This is the most frequently issued warning. But these also often are funnel clouds that don’t result in much, if any, damage. Those warnings now clearly will list that the tornado has not been confirmed and say what and where any potential danger is located.

• When there is evidence of a large or otherwise dangerous tornado, the warning will include the phrase “this is a particularly dangerous situation.” Forecasters hope that will convey a high-threat level. This warning always will include language warning of “considerable damage” being possible.

• When the public or storm spotters report that a definite tornado exists likely to produce devastating damage, the warning broadcast to radio, TV, websites and smartphones will announce a “tornado emergency” and direct the public to seek shelter immediately. That warning always will use the phrase “catastrophic” to describe possible damage. This highest threat level will be reserved for the biggest storms, like the deadly EF-5 that struck Joplin, Mo., in 2011.

“It’s a new way to better describe the seriousness of the situation,” said Carol Christenson, warning coordination meteorologist for the National Weather Service in Duluth. “All tornado warnings, we want people to take them seriously. But there are times when, if we don’t have confirmation of a tornado, the call to action for that situation might be different than a huge EF-5 tornado we know is on the ground barreling toward a populated area.”

The same system of grading the potential impact of the storm will be used to tier severe thunderstorm warnings, which are more common than tornado warnings in northeast Minnesota and northern Wisconsin, Christenson said. Severe thunderstorms already known to be producing 100 mph straight-line winds with baseball-size hail will get a higher threat level than those with heavy rain and quarter-inch diameter hail, she said.

Christenson said the new system comes after the Weather Service enlisted social scientists and human-behavior specialists to find out what specific words are most likely to spur people to action. Even though there were ample warnings issued for the Joplin tornado, many people chose not to take cover and 160 people died.

“When it does get bad, we want people to take action. We’re hoping this conveys the seriousness of the most-serious events,” Christenson said. “When we issue warnings and 160 people died anyhow, that left us wondering what we could do better to get people to act.”

The effort follows a weather service move several years ago to shrink the area covered by each storm warning. Instead of issuing a warning for an entire county, as was previously done, most counties are separated into multiple zones so the warning is issued for a specific area where the storm is located or is headed and “reduce the cry wolf or false alarm syndrome,” Christenson said.

Social behavior has played an increasingly important role in meteorology in recent years as forecasters help citizens and emergency officials “assess their vulnerability” in each storm. Emergency managers in Kansas and Missouri said they liked last year’s test run, reporting that the more descriptive warnings gave them more insight into what a forecaster was thinking.

The nine other states joining the Impact Based Warnings project are Colorado, Illinois, Indiana, Iowa, Kentucky, Michigan, Nebraska, South Dakota and Wyoming. Now all of the most tornado-prone states in the nation are included.

“This project was born out of the recognition that language matters, and how we convey risk can mean the difference between life and death during a weather emergency,” John Ogren, acting director of the National Weather Service’s Central Region, said in announcing the expansion. “One important lesson we learned from 2011 is that standard one-size-fits-all tornado warnings contribute to public complacency. … These enhanced warnings allow us to ring the bell a little louder in those (most-serious) situations.”

Because of the area’s so-far cool spring, with few if any severe storms, the first time people get to hear the new warnings may be during Severe Storm Awareness Week, April 15-19. Christenson said the new system will be used for a mock tornado warning set for April 18 in Minnesota.


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