Starting Monday, the National Weather Service is adding new “damaging threat” categories to severe thunderstorm warnings when they are issued. They’re implementing this change to better communicate the severity of individual severe thunderstorms.
There are three categories: baseline, considerable and destructive.
The baseline is the criteria that severe thunderstorm warnings are currently issued for: winds up to 58 mph and quarter-sized hail or hail that is 1.00” in diameter.
The considerable threat will be issued when there is wind up to 70 mph and at least golf ball-sized hail or hail that is 1.75” in diameter.
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A destructive threat will be triggered when there is wind up the 80 mph and hail that is baseball-sized or 2.75” or larger. When a destructive threat is issued, you’ll get a Wireless Emergency Alert on your smartphone if you’re within the warned area. These will be just like alerts you already get through your smartphone for tornado or flash flood warnings.
Bryce Williams, who is a meteorologist at the National Weather Service in Boston, explains how they decided to send alerts for some severe thunderstorms, but not all.
“Severe storms are so prolific in the United States in spring, summer, really any time of year that people would get desensitized to it if they got an alert for every one,” Williams explained. “So we talked to social scientists and researches that have looked into how people want to know about the most dangerous storms heading their way.”
Williams goes on to say, “it really could save lives when it comes to those tornado force winds, they just happen to be straight-line wind, those really strong, really large hailstones that could deadly. It’s really going to help us improve safety across the country.”
It's important to note that severe thunderstorms that would meet that destructive criteria are very rare in New England. But remember if a severe thunderstorm warning is issued for your area, you need to seek shelter indoors and away from windows.