Weather Academy: Hail Formation

MONROE, La. (KNOE) - We are discussing a new topic this week on the Weather Academy. Let’s talk about hail formation!

In order to talk about hail, we need to take a field trip inside a thunderstorm. Within the thunderstorm, winds are moving in the vertical and the horizontal. So we have side-to-side winds, but also up and down winds, and you typically see precipitation falling from the storm. Sometimes that precipitation can get caught in the upward moving air of the storm, also known as an updraft. As the updraft carries the liquid water droplets up into the storm, it will reach a very cold layer, or what we call the freezing level. At this level, the liquid droplets will cross past that freezing level. We’ll start to see the liquid freezing into ice, and therefore we’ll have ice pellets. Now they don’t necessarily stay above the freezing level. They can move up and down. It will collide with more liquid water droplets as it moves below that freezing level. And then, as it moves above the freezing level, we will see those liquid water droplets continue to freeze on our original pellets. So basically, what’s happening here is additional layers are building on our original piece of ice. Now, if the water freezes on contact, what happens is air bubbles get trapped, and it appears cloudy. But if the water freezes very slowly, those air bubbles have time to release, and therefore our ice will appear clear. Eventually, all these layers add up, and they continue to add weight to our hailstone.

Once that weight exceeds the force of our updraft, the updraft can no longer hold the hailstone in the air. And so we see the Hailstone fall to the ground. Now it can fall to the ground in many different sizes anywhere from a pea size, all the way up to the size of a grapefruit which is about four and a half inches in diameter. For hail to be considered severe, it must be at least an inch in diameter. So these are typically a little bit more rare compared to the more common ones that we see here in the arkLaMiss, which are the penny size, marble size, as well as nickel. The biggest hailstone ever recovered was eight inches in diameter in Vivian, South Dakota, weighing almost two pounds. Luckily, we don’t see anything like that here in ArkLaMiss, but of course, we’re gearing up for severe weather season, so hopefully, this helped you learn how a hailstone forms in what is considered severe hail.

Join us as we make our own hailstone.

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