July/August 2003
One hail of a storm
An Aurora resident with a handful of hail.
One of these hailstones was the largest ever recovered in the United States. The National Climate Extremes Committee, which is responsible for validating national records, has formally accepted the stone's measurements from the National Weather Service forecast office in Hastings, Nebraska. With a diameter of 17.78 centimeters (7 inches) and a circumference of 47.63 centimeters (18.75 inches), the Aurora stone surpasses the famed hailstone that fell in Coffeyville, Kansas on September 3, 1970.
Even hailstones that didn't break records were easily big enough to bust roofs and gutters in Aurora and make whistling noises as they fell through the air. They left craters in the ground up to 14 inches across and 3 inches deep. “I’ve got a bean field out there,” Glen Obermeier, an Auroran with a particularly large crater on his property, told NCAR staffers. “Who would have thought that there would be something so spectacular in it?”
The hailstones were also big enough to bring back memories. "I'll never forget the first hailstorm I was in as a kid back in '39 on Dad's farm," said Don Ward of Aurora. "The hail ruined our corn harvest. The next day, the banker said that was it. It was the end of the farm."
Not surprisingly, the hailstones caused almost as much of a stir at NCAR as they did in Nebraska. Nancy Knight, semi-retired NCAR expert on hail and ice, drove to Aurora on 1 July with UCAR photographer Carlye Calvin to retrieve hailstones that residents had stashed in their freezers and were willing to donate in the name of science. They chatted with Aurora residents, and Nancy told stories about the famous Coffeyville stone from 1970.
Nancy Knight examines a hailstone in NCAR’s cold room.
Previously the largest known hailstone to fall in the United States, the Coffeyville stone weighed .75 kilograms (1.65 pounds) with a diameter of 14.4 centimeters (5.7 inches) and circumference of 44.7 centimeters (17.6 inches). Nancy and her husband Charlie were the principal researchers who measured the stone. The stone no longer exists, but replicas of it can be found at NCAR and at the Dalton Defenders Museum in Coffeyville. It still holds the record for the heaviest U.S. hailstone, since it outweighs the Aurora stone.Nancy served as special consultant to the committee that certified the Aurora hailstone as the nation's largest. She brought a sampling of the Aurora hailstones back to NCAR's cold room in a cooler with dry ice. Repeating the same procedures she and Charlie used on the Coffeyville stone, she weighed them and made precise measurements across thin sections of their diameters.
"It's not as easy as you might think to accurately size a large hailstone because of its irregular shape," she says. "Measuring its mass is more straightforward." •Nicole Gordon
Aurora resident Don Ward lost a chunk of his roof in the storm.
Also in this issue...
Delphi Question: Priarie dog display
NCAR names two new senior scientists
