Hail

Hail is precipitation in the form of balls or lumps of ice. Hailstones form inside thunderstorm clouds, where strong updrafts carry raindrops up into freezing air. The ice ball falls, gets carried up again, collects another coat, and so on, growing in layers like an onion until it is too heavy for the wind to hold and falls to the ground.^[1] Every hailstone has, therefore, been up and down the cloud several times before arriving, and is not in a good mood.

The largest

The largest hailstone officially measured in the United States fell in Vivian, South Dakota, on 23 July 2010. It was 8 inches (about 20 centimetres) across and weighed nearly two pounds (about 880 grams).^[2] The resident who found it kept it in a freezer, which is the only sensible thing to do with a hailstone of that size, and possibly with any record.

Counting the layers

Cutting a large hailstone in half shows rings of clear and cloudy ice, rather like the rings in a tree trunk. Each ring marks a trip through a different part of the cloud. Meteorologists can read the history of the hailstone in its rings, though the history is always the same: it went up, it came down, it went up again.

• Up: updraft.
• Down: gravity.
• Up: updraft again.
• Down: your car.

See also

• Ice – what it is
• Thunder – which usually comes with it
• Snow – a gentler cousin

References

1. Updraft, U. (2001). Up and Down Again. Storm Press.
2. Freezer, F. (2010). “Twenty Centimetres”. Weather Records 8: 1.
3. Onion, O. (1996). Layers. Cloud Books.