Friday, July 30, 2010

Largest Hailstone in U.S. History Just Recorded

A week ago, on Friday, July 23, 2010, a severe thunderstorm hit the town of Vivian, South Dakota. That storm ended up not only producing hail, but the largest hailstone to ever be recorded as long as records have been kept.

The hailstone, as seen on the left, was an amazing 8" in diameter and weighed 1.9 lbs.

The previous record for the largest hailstone recorded occured back in 2003 in Aurora, Nebraska, when a hailstone measured 7" in diameter.

To give you some perspective on how big that hailstone was, here is a chart comparing hail size to a real object.

1.75"---Golf ball
8.00"--Vivian, SD hailstone this past week.

If you had to put a description of how big 8" diameter hail is, it is roughly the size of a volleyball.

Golf ball size hail can put small dents in your car and cause minor roof damage. Baseball size hail can put holes in your windshield, do severe damage to your vehicle, and completely ruin your roof.

Just imagine the kind of damage the size of this hailstone could do?

So how can hail become that big? It ultimately depends on the updraft of a thunderstorm, or how fast air is rising based on a very unstable atmosphere.

Below is a brief chart of how strong the updraft speed has to be in order to generate these large hail cores.

Hail Size: Updraft Speed:
Baseball 90 mph
Softball 110 mph
Soccer ball 190 mph

The bottom line is in order for a thunderstorm to produce large hail, you need a very unstable atmosphere and very cold air in the mid to upper levels of the atmosphere. As air rises, it cools and condenses into water droplets. If the vertical motion is strong enough, some of these droplets can freeze and combine with other water molecules to form hail.