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Back in July 2010, a monster hailstone plummeted to Earth from a slate gray South Dakota sky. It was found by ranch hand Leslie “Les” Scott near a small town of about 100 people named Vivian, on the high plains of South Dakota.

The hailstone was 8 inches in diameter and weighed almost 2 pounds! That broke the previous record for North America, when a 7-inch hailstone smashed down in Aurora, Nebraska, in June 2003.

I spoke with Leslie Scott about the hailstone discovery at his home near Schoolhouse Hill in Vivian.

That day, Leslie spotted a “finger tornado” while he was working and decided to head home. A few minutes later, Leslie and his wife, Debra, heard what sounded like bricks smashing against their home from an angle. What they heard that evening were enormously large hailstones, which smashed through their roof, leaving baseball-sized holes in their ceiling, and broke out many of their windows.

After the deafening noise stopped, Leslie and Debra ventured outside and saw countless large hailstones lying on the ground.

“One hailstone caught my eye because it had numerous fingers of ice sticking out of it, but there were other stones that size and even bigger that fell,” he said.

Leslie took the hailstone and placed it in his freezer. He told me it melted somewhat because he lost power to his home after the storm.

A meteorologist from the National Weather Service retrieved and sent this record-breaking chunk of ice to the National Center for Atmospheric Research in Boulder, Colo. The National Climate Extremes Committee confirmed the record weight and diameter. By the way, the world record belongs to a 2.25-pound hailstone that fell in Bangladesh in April 1986.

So, how are these monster hailstones formed?

Hail is produced in cumulonimbus clouds, otherwise known as thunderstorms. Strong updrafts within the cloud will keep supercooled raindrops suspended thousands of feet in the sky. Supercooled liquid will freeze on contact with particles like dust or even insects and grow larger and larger in the strong updrafts as they collide with other supercooled liquid droplets.

When the hailstones become too heavy to be supported by the updrafts or carried away by winds aloft, they fall to the Earth. Often in Santa Barbara County, hail will melt before reaching the ground. However, growing amounts of sunlight in April and May heats the Earth’s surface, which in turn warms the surface air and causes it to rise into the atmosphere. This convection circulation can severely destabilize the atmosphere as the relatively warm air slams into the cold air above, which can produce thunderstorms and hail.

The hailstone that Leslie found probably took violent updrafts that exceeded 160 miles per hour to remain suspended in the cloud over the course of five to 10 minutes!

“It just wasn’t my house. The whole community was hit really hard,” Leslie said.

Please join us, Pacific Gas and Electric Co. employees Saturday, April 13, to celebrate Earth Day at Montaña de Oro State Park. The event is one of a number of service projects sponsored by PG&E and the California State Parks Foundation. If you plan to join us, register at the California State Parks website, Rangers will provide tools and supervision at the event.

John Lindsey is PG&E’s Diablo Canyon Power Plant marine meteorologist and a media relations representative. Email him at or follow him on Twitter: @PGE_John.


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