We’ve had some hearty monsoon thunderstorms this season, with plenty that included some hail.
We don’t see it too often in Phoenix, but if the conditions are right, these little balls of ice can fall from the sky.
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So how does hail form?
It’s quite similar to a snowball rolling down a hill, but kinda the opposite direction.
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Hail is formed when thunderstorm storm updrafts are strong enough to thrust water droplets high in the atmosphere above the freezing level.
The temperature cools with height in the upper reaches of the atmosphere, and when water droplets are pushed up there, they freeze.
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This freezing process is the start of hail formation.
Much like a snowball, it starts pretty small and then grows and grows as it rolls downhill collecting more and more snow on the outside layer.
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A hailstone does the same thing. A hailstone forms in the freezing temperature and then begins to fall.
Those thunderstorm updrafts (upward moving air in a storm) continue to toss the hailstone into the air, each time coating it with another layer of ice.
Eventually, after several coatings of ice, the hail becomes too heavy for the updraft and the stone falls to the ground.
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The strength of the updraft will determine how big the hail is. The stronger the updraft, the more times the hail is coated before it falls to the ground.
In 2010, a very destructive hailstorm hit Phoenix, causing nearly $3 billion in damages. That was one of the costliest hail storms ever in the United States.
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