## Hail’s damaging effects tricky to predict

March 11, 2009

Dave Ozaki, American Family Insurance physical damage examiner, Lawrence, gets an eye-level view of the dents and depressions of hail damage on the roof of a vehicle following an April 2006 storm.

This hailstone, nearly the size of a baseball, fell in the 600 block of Maine Street in Old West Lawrence during an April 2006 storm.

#### Storm tip

It’s often tricky to get an accurate measurement of the diameter of hail while it’s falling, according to the National Weather Service.

But the government’s weather agency said the following table can help you estimate the size of hail by comparing it to the average diameters of common items:

• Pea = 1/4 inch • Marble/mothball = 1/2 inch • Dime/penny = 3/4 inch • Nickel = 7/8 inch • Quarter = 1 inch • Ping-Pong ball = 1 1/2 inch • Golf ball = 1 3/4 inches • Tennis ball = 2 1/2 inches • Baseball = 2 3/4 inches • Tea cup = 3 inches • Grapefruit = 4 inches • Softball = 4 1/2 inches

It can shower down looking like peas, golf balls, oddly shaped pancakes or anything in between.

The weather phenomenon known as hail can be destructive, big and sometimes deadly.

The frozen ice chunks are typically less than 2 inches in diameter — or smaller than a golf ball — when they reach ground. But hail can also be as big as a baseball, softball or even larger.

The National Weather Service considers hail with a diameter larger than an inch — about the size of a quarter — to be severe. It’s hail of this size that could cause someone to be injured as the blobs of ice race to the ground at speeds that can reach 120 mph.

But even the small stuff can be hazardous, said Dennis Cavanaugh, NWS meteorologist in Topeka.

“Small hail driven by 70 mph winds is still incredibly dangerous,” he said. “Not only would it hurt a lot, it could cause property damage.”

Hail causes \$1 billion in damage to crops and property each year, according to the NWS.

There is no science to measuring hail. It’s generally measured by finding the largest piece that fell and comparing it to the size of a coin or a common sports object, such as a golf ball, baseball or softball.

“These are things that people are all familiar with. They know how big these objects are,” said Donna Tucker, Kansas University associate professor of geography.

Sometimes more than one hail stone will be fused together before falling to the ground. The entire object is measured together because of the weight it adds to the stone, which can in turn cause more damage when it falls, Cavanaugh said.

The city of Manhattan was hammered by softball-sized hail — measuring 4 1/2 inches in diameter — during a storm June 2, 2008. Hail of that size is rare and quite destructive.

The largest recorded hailstone fell June 23, 2003, in Aurora, Neb., according to the NWS. It was 7 inches in diameter, had an 18 3/4-inch circumference and weighed just less than 1 pound. The heaviest hailstone — weighing 1.67 pounds, with a diameter of 5.7 inches and a circumference of 17 1/2 inches — fell Sept. 3, 1970, in Coffeyville.

Tucker said hail is most commonly seen in the United States in areas of northeast Colorado and southeast Wyoming. It’s a weather event that’s difficult to predict.

“We don’t know as much about forecasting hail as we know about forecasting tornadoes, or even strong winds,” Tucker said. “There just hasn't been a lot of research done on hail.”

She said funding for hail research has been limited, because the phenomenon doesn’t have a big history for killing people — like tornadoes do.

6News chief meteorologist Matt Elwell contributed to this report.