VIVIAN, SD – Parts of our area have seen pea-to-nickel-sized hail this past week, which is pretty common in summer storms. It was around this time of year, on July 23, 2010, when the largest hailstone recorded fell in Vivian, South Dakota.
The National Weather Service in Aberdeen measured it to be 8″ in diameter, which is approximately the size of a volleyball!
It weighed nearly two pounds too.
In a press release, they said this broke the previous record of a 1970 hailstone in Kansas that weighed 1.67 pounds and a 2007 hailstone in Nebraska that was 7″ in diameter.
And to think...there was a power outage afterward that caused the Vivian stone to melt prior to official measurement.
How does hail grow?
A hailstone of 1″ in diameter or higher is considered “severe.”
Thunderstorms originate from an updraft, or rising air. Generally, the more quickly this air rises, the larger that hail can grow. The National Weather Service in Aberdeen estimates that the updraft that caused this hailstone ranged between 160 and 180 mph!
In addition to hot and humid air at the surface that allows the air to rise, there needs to be a sufficient amount of cold air in the highest parts of the storm. It’s estimated that temperatures at the top of this storm were more than 90°F below zero.
This violently rising air, in addition to very cold air thousands of feet up, allowed the hailstone to continue to grow so large before falling out of the cloud.
Thankfully, no one was hurt.