When hail hurts

Back when News Cut was a young boy, he traveled to the top of the Empire State Building, where his sister told him if he threw a penny off, it would make a crater in the streets of Manhattan below. Then, as now, News Cut didn’t have any money to throw, but the image has persisted. Then, as now, News Cut’s sister was in error.

So when we heard today that golf-ball sized hail fell in Backus (and it’s heading East), we were naturally inclined to figure out how big of a hole a golf ball could make, if a penny could take out 42nd Street.

We really only have estimates about the speed hail falls. One estimate is that a 1cm hailstone falls at 9 m/s, and an 8cm stone, weighing .7kg falls at 48 m/s (171 km/h). However, the hailstone is not likely to reach terminal velocity due to friction, collisions with other hailstones or raindrops, wind, the viscosity of the wind, and melting. Also, the formula to calculate terminal velocity is based on the assumption that you are dealing with a perfect sphere. Hail is generally not a perfect sphere!

Another factor in assessing the danger of hail is how fast the wind is blowing that might make them speed toward earth.

In any event, the golf-ball sized hail likely presents less of a danger than, say, a golf ball. Unlike the example above showing a .7kg object travels 108 mph (175 km/h), a golf ball weighs a fraction of that — about .04 kg, and travels about 125 mph when someone who knows what their they’re doing hits it. So a driven golf ball likely presents more of a danger than a falling one.

People are killed by hail. We just don’t hear about it much. In Egypt in February, four people were killed by hail. But the last U.S. death from hail on record was in 1979. A man went out to move his new car out of the hailstorm, when he was hit.

But while rare, death by golf ball has occurred more recently.

And yet, we’re not interrupting programming today to warn you about the guy on the 7th hole.

• Allison

I was in Cairo during that fatal hailstorm. Cairenes told us there hadn’t been hail in Cairo for a generation. I’m one of those Midwesterners who find storms thrilling. In this case, I was sad that it cut short my once-in-a-lifetime feluca trip on the Nile; I am even sadder now to know that people lost their lives.

(But thanks for posting this story. I looked in vain after the storm for some analysis. This is the first I’ve seen.)