Hail is often associated with thunderstorms but not just any thunderstorm. Hail is associated with stronger thunderstorms where the updraft is strong enough to keep hail stones suspended in the atmosphere without falling to the ground.
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An updraft is an upward current of air, flowing from the ground up into the storm cloud. Updrafts can be in excess of 100 mph! The stronger the updraft, the longer the hail stones are suspended aloft and the bigger it gets.
So how does hail form?
Hail forms from raindrops that are carried upward by the updraft into a very cold part of the storm where it freezes into a tiny ball of ice. The hail stone will circulate within the storm cloud until it becomes too heavy for the updraft to support it. As the hail stone tosses around in the storm cloud, it collides with many other super cooled water droplets. Super cooled water droplets are tiny particles of water that are cooled below their freezing point. When the tiny hail stone collides with super cooled water droplets, the droplet instantly freezes on the hail stone, allowing the hail stone to grow in size. This process is known as accretion.
Once the hail stone becomes too heavy for the updraft to keep it suspended in the air, it will come crashing to the ground. Hail stones that are roughly one inch in diameter (quarter size) or larger are known to cause damage. They can make the surface of a vehicle look like the surface of a golf ball. Very large hail stones such as baseball-size hail can fall at speeds near 100 mph, busting out windows and causing lots of damage. Hail this size may be lethal if you’re caught out in it.
Here’s a fun fact. The largest hail stone ever recorded in the United States was found in South Dakota back in 2010. It was 8 inches in diameter and weighed nearly 2 pounds! That’s about the size of a volleyball!
If you split a large hail stone in half, you can see many rings on the inside. It kind of looks like rings on a tree. Each ring in a hailstone represents how many times that hail stone circulated around the cloud before it came crashing down to Earth. Pretty cool!
Meteorologists often refer to hail sizes by using a list of common reference items.
Hail Sizes (diameter):
· Pea: ¼ inch
· Marble: ½ inch
· Penny: ¾ inch
· Quarter: 1 inch (This size is considered severe)
· Pingpong ball: 1.5 inch
· Golfball: 1.75 inch
· Baseball: 2.75 inch
· Grapefruit: 4 inch
· Softball: 4.5 inch
Most hail stones are small and it’s very difficult to have large hail in Florida. It’s not because we lack thunderstorms. Florida receives more lightning than any other state in the U.S. However, our freezing level is much higher in altitude than over South Dakota. Therefore, hail stones don’t have the same opportunity to grow large in size. In addition to Florida’s warmer climate…a lot of the hail that does form melts as it falls toward the ground.
There are times where storms can produce large hail over Florida. Look back to April 10, 2018 when a nasty thunderstorm dropped hail larger than baseball size (3 inch diameter) near Jacksonville. Large hail can happen and when it does, it usually happens in the spring when our freezing levels are low.
Let’s demonstrate how hail forms in this easy to do experiment!
Experiment: How Hail Forms
Purpose: To demonstrate how hail forms and grows within a thunderstorm
What you need:
- Glass cup, beaker or glass measuring cup
- Lots of salt
- Glass test tube
- Tap water
- Purified water
- Ice cubes
- Metal stir rod
1. Fill the glass cup 2/3 of the way with tap water
2. Pour a lot of salt into the cup, enough where you can see salt grains on the bottom of the cup. You can’t have too little salt.
3. Fill the rest of the cup with ice
4. Use the metal stir rod to mix the ice and salt water
5. Place purified water into the test tube
6. Place the test tube into cup of salt water
7. Every minute for the next 6-7 minutes, stir the ice water around
8. After 7 minutes, removes the test tube with the purified water and place a small piece of ice into the tube.
9. Congrats, you just made hail!
Results: The super cooled water inside the test tube instantly froze when the small piece of ice was added to the test tube.
Conclusion: Hail grows when it comes into contact with super cooled water. In this experiment, the salt lowers the freezing point of water, allowing the water inside the test tube to be super cooled. Once the small piece of ice came into contact with the super cooled water, the water instantly froze over. This is significant in the real world because when a piece of hail comes into contact with super cooled water droplets, the hail stone will grow larger. The longer the hail stone circulates in the cloud, the larger the hail stone will become.