SWAW: All hail the hailstone!
Posted February 28, 2011
Can you imagine a chunk of ice that measures 18 inches around and weighs two pounds falling from the sky? Well, it happened last year in Vivian, South Dakota. On July 23, 2010 this small town was thrust into the worldwide spotlight after massive hailstones fell from a thunderstorm that hot afternoon, and some went down as the world's largest! Eyewitnesses said the hailstones were so large they left dents in the ground -- some as large and as deep as coffee cans!
Fortunately for us, North Carolina rarely sees hail larger than golf balls. From time to time though, we see reports of tennis ball and baseball sized hailstones! As part of Severe Weather Awareness Week in North Carolina, we are reminded of the ferocity of thunderstorms and what kind of impact they can have.
New Hail Criteria
In 2010 the National Weather Service redefined the hail criteria for severe thunderstorms. Hail stones must reach at least one inch in diameter, or the size of a quarter, to be classified as severe. Prior to this change, hail three-quarters of an inch in diameter (or penny sized) was considered severe. The increase in severe hail criteria resulted in a reduction in the number of warnings issued for hail. In fact, only 23 hail events produced hail quarter size or larger in Central North Carolina last year. On average, only about 40 percent of all hail reported is quarter size or larger.
Hail season typically runs from March through July in North Carolina with May usually being the month with the greater number of hailstorms.
Wind Also a Threat
The wind criteria for a severe thunderstorm, 58 mph or greater, remains unchanged. The season for storms with damaging winds runs from March through September, with the most notable storms from May through August.
The National Weather Service says severe gusts of wind from a thunderstorm called downbursts or straight-line wind are a serious danger. Nationally over the last 30 years, nearly as many people have been killed by straight-line winds as from tornadoes. Thunderstorm wind gusts rush down from the storms sometimes reaching speeds in excess of 100 mph. Thunderstorm winds of this magnitude affect large areas and cause widespread damage and injuries from flying debris. Straight-line winds can cause damage equivalent to that of a weak tornado.
To protect yourself from severe weather it is advisable to pay attention to the weather around you and be aware of quickly changing weather conditions. In the event you see dark skies and hear the rumble of thunder, seek shelter and remain indoors until 30 minutes after the last rumble of thunder. Being indoors offers the greatest protection from hailstones and severe wind gusts. It takes personal responsibility on your part and vigilance to make sure you are safe from severe weather. North Carolina offers many outdoor activities; make sure you remain informed about the weather when enjoying your favorite sports and hobbies. Be aware and be safe this severe weather season.