Everything You Needed to Know About...Hail!

6/7/2018 (Permalink)

1. Hailstorms are statistically one of the most costly natural disasters

    As stated in "Hale Depot", according to the National Weather Service, hail results in some of the highest rates of property damage in terms of natural hazards. In 2015, hail caused 586 million dollars in property damage, and in 2016, hail caused 3.5 billion dollars in damage.

2. Hail does not immediately fall after it forms

   Hail forms inside the clouds of a thunderstorm, and actually begins as just a tiny drop of supercooled water. This just means that it is below freezing temperatures, but still in a liquefied form. If it stays at this extra cold temperature for long enough, it will eventually freeze and solidify into a small hailstone. The tiny ball of ice still isn’t heavy enough to fall yet and remains suspended in the thundercloud by an updraft caused by the storm. These hailstones tumble around and collect more condensation, which freezes and makes the hailstone bigger – kind of like rolling a snowball around in the snow to make larger. Once the stone becomes too heavy to stay afloat, it falls to the ground.

3. There is a threshold for what is considered “severe” hail

   The National Weather Service classifies “severe” hail as being at least 1-inch in diameter, about the size of your average gumball. It seems like a lot of hail storms are considered severe because that’s what we see on the news, but most hailstorms involve hailstones that are closer to the size of peas. Even hail that does not reach the “severe” state can still cause damage to cars and injure people.

4. The largest hailstone ever recorded was the size of a volleyball

   We often refer to sizes of hailstones in terms of recognizable, everyday objects. We’ve already done it in this article! For some perspective, a hailstone that is 1 inch in diameter is the size of a gumball. After that, a hailstone that is 1.5 inches is most recognized as the size of a ping-pong ball, and next comes some golf ball-sized hail at 1.75 inches across. When people talk about “baseball-sized hail,” they’re referring to hailstones that are about 2.75 inches in diameter. The largest hailstone ever recorded was bigger than a baseball. It was bigger than a softball. 

5. Hail happens most often during the summer

   No, it isn’t opposite day. Even though balls of ice fall from the sky during a hailstorm, these occurrences are actually most common during the summertime and warmer months. So why does this happen? Hail forms inside of thunderclouds, so there need to be proper atmospheric conditions that support both thunderstorms and hail. This happens in the early months of summer when the ground temperatures are warm, but temperatures in the upper atmosphere are cold enough to form ice. The greater the contrast between upper and lower temperatures, the stronger the updraft of the storm will be. Stronger updrafts can suspend hailstones for longer periods, meaning that the ice continues to collect and grow the hailstone bigger until they eventually fall. That’s why warm summer months are the perfect time for hail to form and ultimately fall.

6. Hailstones fall fast… really fast

   The bigger the stones, the faster they fall. Hail often falls so fast that it doesn’t really lose a lot of mass between when it leaves the thundercloud and when it reaches the ground. The speed at which hail is falling when it hits the ground is often referred to as terminal velocity, and this speed varies depending on the size of the hailstone. A hailstone that is about 1 centimeter in diameter has a terminal velocity of about 20 miles per hour. What about a stone the size of a baseball? This size of hail can hit the ground at a walloping 100 miles per hour. To put that into perspective, the fastest fastball baseball pitch ever recorded was clocked at 105.1 miles per hour. So if you ever find yourself stuck in a hailstorm of any proportions, please take cover.

7. There is a place called “Hail Alley”

   You’ve probably heard of Tornado Alley, where tornadoes frequently occur, but did you know there is a Hail Alley as well? We talked above about how hail forms in thunderstorms. It would follow that the areas that receive the most hail are places that have the most thunderstorms – like Florida. However, Colorado, Nebraska, and Wyoming report the most hailstorms, and the region where these states meet is called Hail Alley. This is because these states have high elevations where parts of the atmosphere that remain below freezing temperatures are closer to the ground, meaning the hail is more likely to stay frozen as it travels to the earth. Internationally, China, Italy, Russia, and India also receive large amounts of hail storms each year.

8. You can tell how many times a hailstone circulated a thundercloud by cutting it in half

   You’ve probably heard about tree trunks having rings inside that help you determine how old the tree is, but did you know that if you cut a hailstone in half, you can also see rings in the cross-section. These rings form when new layers of ice freeze on the hailstone, and usually alternate between clear and milky white. Scientists believe that the clear layers occur when the stone is at the lower end of the thundercloud where the temperature is slightly higher. This makes the water freeze more slowly and appears clear, just like when you make ice cubes in your freezer at home. The milky layers are thought to form when the hailstone is at the top of the cloud where temperatures are well below freezing. This means that water droplets freeze almost immediately upon contact with the hailstone, creating white air bubbles.