Thunderstorms, which can be life-threatening, are not all the same, and varying hazardous conditions include tornadoes, flash flooding and large hail, the weather service said. The agency believes it will better be able to convey the severity and potential impact of the thunderstorms by adding a "damage threat" tag to severe thunderstorm warnings like it does for its tornado and flash flood warnings.
The three categories the weather service developed, which are ranked from highest to lowest, are "destructive," "considerable" and "base." The tags and additional messages are designed to spur immediate action, based on the threats.
The addition of damage threat tags, which the weather service implemented on Aug. 2 , are part of the broader Hazard Simplification Project to improve communication of watches and warnings to the public.
"This is kind of analogous to tornado warnings where you can be reached anywhere," said Carl Jones , a meteorologist at the National Weather Service in Grand Forks. "Some of these storms can be just as impactful as these tornadic systems."
The warning includes a "call to action," which describes what the public should do when it receives the warning. That includes going indoors to the lowest floor of a building and staying in the center, away from windows, Jones said.
In 2020, 13 of the costliest weather disasters, including the Iowa derecho that caused $11 billion in damage, were severe thunderstorms. The new "destructive tag," would have activated a wireless emergency alert for those storms, the weather service said.
The categories' criteria are:
Destructive: Baseball-sized hail (hail that is at least 2.75 inches in diameter), and/or 80 mph thunderstorm winds. Warnings with the destructive tag will activate a wireless emergency alert on smartphones within the warning area.
Considerable: Golf-ball sized hail (hail that is 1.75 inches in diameter) and/or 70 mph thunderstorm winds. The warning will not activate a WEA.
Baseline: The warning is unchanged and is quarter-sized hail (1-Inch) and or 58 mph thunderstorm winds. The warning will not activate a WEA. When there is no damage tag on a warning, damage is expected to be at the base level.
An average of about 10% of severe thunderstorms, nationwide, reach the destructive category each year, the weather service said. Most of the storms that cause damage are wind events, such as derechos and some larger, more intense thunderstorms called "supercells," which produce large hail.
NOAA Weather Radio. weather.gov, Emergency Alert System and dissemination systems to emergency managers and partners will continue to issue and distribute severe thunderstorm warnings to the public.
___
(c)2021 the Grand Forks Herald (Grand Forks, N.D.)
Visit the Grand Forks Herald (Grand Forks, N.D.) at www.grandforksherald.com
Distributed by Tribune Content Agency, LLC.
