On this date in 2021 hailstones the size of golf balls hit Essex. 10 things you might not know about hail:
Hail is formed in thunder clouds where there can be winds blowing upwards. The temperature in these upper reaches of clouds can be below freezing, so raindrops forced upwards by the updrafts into this zone will freeze into hailstones.
This can happen several times as the hailstone catches the upward wind again on its way down. One source described hailstones in a cloud as being like balls in a lottery machine. The process is repeated until the ball of ice is too heavy for the wind to blow it back up and that’s when it falls to earth. Hence, the stronger the wind in the cloud, the bigger the hailstones. According to the US National Weather Service, upward wind speeds of 64 mph will support a hailstone as large as a golf ball, while a Grapefruit-sized stone needs a 98-mph updraft.
In order for hail to form the temperature of the top of the cumulonimbus cloud must be colder than -20C.
If you cut a large hailstone in half it has rings, like an Onion or a tree trunk, so you can tell how many times it bounced to the top of the cloud. Some rings are milky White while others are clear. Clear layers form when the hailstone is in a part of the cloud where the air temperature is just below freezing so the water slowly freezes over the hailstone and air bubbles can escape. Opaque layers of ice form when the air temperature is well below freezing and a water droplet freezes immediately upon colliding with the hailstone, trapping the air bubbles.
An ice crystal with a diameter of more than 5 mm (0.20 in) is considered a hailstone.
They can get a lot bigger than that. The largest hailstone in the UK fell in Horsham, West Sussex, on 5 September 1958 and weighed 142g. In the US an even bigger one fell in Vivian, South Dakota on 23 July 2010. It weighed 0.88kg and was 20cm in diameter, about the size of a volleyball.
Needless to say, hailstones that big can cause a lot of damage as they can fall at speeds ranging from 44 to 72 mph and some monsters might even reach 100mph. This can damage buildings, vehicles parked outside, crops and can even kill people. 250 people in India were killed by falling hail in 1888.
Mountain ranges and high elevations in mid latitudes get the most hail. In North America, hail is most common in the area where Colorado, Nebraska, and Wyoming meet, This is known as "Hail Alley". Central Oklahoma has reported the most 1-inch-plus hail events in the U.S. since 2015, with over 2,200. In Europe, southern and western Germany, northern and eastern France and northern Italy get the most hailstorms, but the world prize goes to Kericho, Kenya, which experiences hailstorms, on average, on 50 days annually. Kericho reached the world record for 132 days of hail in one year.
In the UK, we get hail in summer. Hail in winter is more likely to be graupel, which is softer than hail and forms when supercooled water droplets add a layer of ice or rime to falling snowflakes.
In the Middle Ages, church bells would be rung in an attempt to prevent hail and preserve the crops.
Character birthday
Dorothy Mayfield, Ultra Grav’s mother.
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