Kids of all ages will enjoy safely participating in this science experiment as they watch “hailstones” fly through the air. It’s time to dive in and learn How Does Hail Form.
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I loved using this demonstration to teach elementary students about the water cycle and how hail forms when I was a Broadcast Meteorologist. Now I get to show you how to make a hail storm with a few supplies from your own home!
How Does Hail Form
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Supplies Needed:
- Electric hair dryer
- Ping pong ball
- Bag of assorted size Styrofoam balls
- A large 4″ of 5″ Styrofoam ball
Steps:
- Plug your electric hair dryer into a wall outlet
- Grab the smallest styrofoam ball and see if you can make it float
- Use a ping pong ball to show how the density and size of a hailstone can vary
- Move to the next size up and see if the ball can still float in the air
- Continue the process until you get to the biggest ball that will not float
- Hold the hair dryer at a 45° angle and see if the ball will stay in the air
Step 1: Plug in your hair dryer
Find a good open area to plug your hair dryer into a wall outlet. If you are doing this as a demonstration to a large classroom of students, you will want to be in the front of the room where everyone can see.
Depending on the set up of the room, you might need to use an extension cord to allow you to be in a good visible location.
Step 2: Start with the smallest ball and make it float
This is the part where we are going to pretend that the styrofoam balls are hailstones flying around in a big thunderstorm cloud!
Go ahead and hold your hair dryer so that the air is blown directly upward. From your collection of styrofoam balls place the smallest ball on the hair dryer and turn it on high to simulate a hailstone being suspended in a thunderstorm updraft.
If you have a lot of little ones as your audience, or a class full of students, you might want to ask for volunteers to “place the hailstone in the cloud.” The kids always get a kick out of this and watching the hail fly through the air!
Step 3: Use the ping pong ball to see how high it will go
After you have wowed your audience with the high flying smallest “hailstone,” turn off the hair dryer and let the styrofoam ball fall to the ground. This will represent the thunderstorm updraft weakening enough for the hail to fall to the ground.
Now grab a ping pong ball out of your assortment of balls and explain that not all hailstones are the same size or density for that matter. The different material that the ping pong ball is made from will cause a slightly different result than a styrofoam ball of the same size.
Believe it or not, when the right atmospheric conditions are present in a thunderstorm, some hailstones can actually be very clear and transparent, while others take on more of a white look. We will learn more about this later, but for now lets move on to an even bigger hailstorm!
Step 4: Grab the next biggest styrofoam ball and try again
By the time we have gotten to this step you should start to see a pattern with how high the balls are able to fly. As the balls, or “hailstones” get bigger and bigger they are not able to be pushed as high into the cloud.
The ball should still float in this step, but it just won’t be soar quite as high as the smallest ball.
Overtime these hailstones are accumulating more and more ice and getting bigger and heavier. Eventually, they will get heavy enough that the thunderstorm updraft will not be strong enough to fight the gravity and the icy ball will fall to the ground.
Step 5: Use the biggest ball you have and see if it will be too heavy to float in the updraft
Nobody ever want’s to get caught in a hailstorm with a hail stone this size! Go ahead and pull the biggest ball (should be around 5 inches diameter) in your collection out of the bag and see if it will float.
Depending on the strength of your hair dryer, your massive pretend hailstone will likely hover just above the air discharge on the hair dryer before falling to the ground.
We can now really see the effect that gravity has on a hailstone as it gets larger and heavier. Even though the thunderstorm updraft is just as strong as before, the hailstone has become so heavy that it just can’t stay in the cloud any longer and it crashes to the earth at an incredible speed!
Step 6: Hold the hair dryer at a 45° angle and make the ball spin
Full disclosure: I added this step after accidentally doing this one time in front of a classroom of first-graders and was shocked at what happened!
Use the biggest ball that you have again and place the ball into the updraft from your hair dryer. Once the ball is trying to float, very slowly and carefully tilt the hair dryer to a 45° angle and see what happens.
If you do this step just right, you will watch in awe as your ball starts to spin very quickly in the current of wind created by the hair dryer. This spinning motion will also help propel the ball away from the hair dryer and remain floating.
This is a great example of wind shear in the atmosphere and how wind direction can change with height in a thunderstorm. If this kind of wind shear is strong enough, it can even lead to tornadoes forming.
What is Hail?
Hail is a type of frozen precipitation that falls from the clouds. Hailstones are made up of balls or lumps of ice. These balls of ice can vary in size from 1/4″ to over 5″ in diameter!
Another way to visualize this is that the smallest hail is about the size of a pea and large hail can be as large as a grapefruit!
Fun Fact: The largest hailstone reported in the United States fell in Vivian, South Dakota on June 23, 2010. It was a whopping 8 inches in diameter and weighed 1 lb 15 oz!
How Fast Does Hail Fall?
The speed of hailstones falling from a thunderstorm depends on the size of the hail, the friction of the surrounding air, the speed and direction of the wind, and how fast the hailstone is melting.
Rough estimates have clocked the largest hailstones falling over 100 mph! Although most small hailstones fall at speeds between 9 and 25 mph. Larger hailstones in Severe Thunderstorms can fall between speeds of 25 and 72 mph.
How Does Hail Form in Warm Weather?
The fascinating thing about hail is that it often falls during the summer months when it is warm outside. Even though the temperature is usually well above freezing at the ground when the hail falls, high up in the atmosphere the air stays very cold.
The warm, humid air on a hot summer day is the perfect recipe for a thunderstorm to develop. As the hot and humid air rises high into the atmosphere it cools and condenses and forms a cloud.
Eventually, the cloud will begin to form water droplets (raindrops). The air rising into the thunderstorm creates an updraft of wind that carries the raindrops into the upper parts of the cloud where it is cold enough to freeze to ice.
This process of the hailstone going up and down in the thunderstorm will continue into the hailstone gets several layers of ice and becomes heavy enough for gravity to win the battle between the updraft and pull the hailstone to the ground.
The strength of the updraft in the storm determines how large the hail will get. The longer the hailstones remain in the cloud and continue getting coated with ice, the larger they will become.
Why Are Some Hailstones Clear?
Different temperatures and liquid water content conditions in a thunderstorm can determine why some hailstones look white, or cloudy, and others look clear.
Because of these conditions in the thunderstorm, hailstones that take on a cloudy appearance have lots of tiny air bubbles trapped within the ice layers.
Hailstones that are clear were able to form in an environment with higher water content and do not have air bubbles trapped between the layers of ice that make up the hailstone.
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