Hail

What is hail?

Hail is a variety of differently shaped ice balls or lumps. Hail or hailstones are made up of water ice and can be any size; it can be measured anything from five millimetres and two hundred millimeters. Hail is produced during thunderstorms and heavy rains.

What is a hailstorm?

A hailstorm is a thunderstorm that produces hail.

How does hail form?

Hail is created when small water droplets are caught in the updraft of a thunderstorm. These water droplets are lifted higher and higher into the sky until they freeze into ice. Once they become heavy, they will start to fall. If the smaller hailstones get caught in the updraft again, they will get more water on them and get lifted higher in the sky and get bigger. Once they get lifted again, they freeze and fall. This happens over and over again until the hailstone is too heavy and then falls to the ground.

How does hail fall to the ground?

Hail falls when it becomes heavy enough to overcome the strength of the updraft and is pulled by gravity towards the earth. How it falls is dependent on what is going on inside the thunderstorm. Hailstones bump into other raindrops and other hailstones inside the thunderstorm, and this bumping slows down their fall. Drag and friction also slow their fall, so it is a complicated question! If the winds are strong enough, they can even blow hail so that it falls at an angle. This would explain why the screens on one side of a house can be shredded by hail and the rest are unharmed!

How fast does hail fall?

We really only have estimates about the speed hail falls. One estimate is that a 1cm hailstone falls at 9 m/s, and an 8cm stone, weighing .7kg falls at 48 m/s (171 km/h). However, the hailstone is not likely to reach terminal velocity due to friction, collisions with other hailstones or raindrops, wind, the viscosity of the wind, and melting. Also, the formula to calculate terminal velocity is based on the assumption that you are dealing with a perfect sphere. Hail is generally not a perfect sphere!

What areas have the most hail?

Though Florida has the most thunderstorms, Nebraska, Colorado, and Wyoming usually have the most hail storms. The area where these three states meet – “hail alley,” averages seven to nine hail days per year. The reason why this area gets so much hail is that the freezing levels (the area of the atmosphere at 32 degrees or less) in the high plains are much closer to the ground than they are at sea level, where hail has plenty of time to melt before reaching the ground. Other parts of the world that have damaging hailstorms include China, Russia, India and northern Italy.

Does hail fall in paths?

When viewed from the air, it is evident that hail falls in paths known as hail swaths. They can range in size from a few acres to an area 10 miles wide and 100 miles long. Piles of hail in hail swaths have been so deep, a snow plow was required to remove them, and occasionally, hail drifts have been reported.

How large can hail get?

Hail is usually pea-sized to marble-sized, but big thunderstorms can produce big hail. The largest hailstone recovered in the U.S. fell in Vivian, SD on June 23, 2010 with a diameter of 8 inches and a circumference of 18.62 inches. It weighed 1 lb 15 oz.

What types of thunderstorms produce large hail?

Supercell thunderstorms have sustained updrafts that support large hail formation by repeatedly lifting the hailstones into the very cold air at the top of the thunderstorm cloud. In general, hail 2 inches (5 cm) or larger in diameter is associated with supercells. Non-supercell storms are capable of producing golf ball size hail.

How is hail measured?

Hail size is estimated by comparing it to a known object. Most hail storms are made up of a mix of sizes, and only the very largest hail stones pose serious risk to people caught in the open.

• Pea = 1/4 inch diameter
• Marble/mothball = 1/2 inch diameter
• Dime/Penny = 3/4 inch diameter
• Nickel = 7/8 inch
• Quarter = 1 inch — hail quarter size or larger is considered severe
• Ping-Pong Ball = 1 1/2 inch
• Golf Ball = 1 3/4 inches
• Tennis Ball = 2 1/2 inches
• Baseball = 2 3/4 inches
• Tea cup = 3 inches
• Grapefruit = 4 inches
• Softball = 4 1/2 inches

Can meteorologists detect when hail is going to form in a thunderstorm?

Meteorologists can predict when thunderstorms are going to happen and can detect hailstorms and hail occurring. This can be done through weather radar imagery and satellites used especially for predicting weather and weather changes. When the hail is created and are larger than normal or average size, then they will fall at greater speeds. However, things such as friction with wind and air; and melting and the hail’s interaction with other hailstones and rain can slow down the speeds.

What kind of damage does hail cause?

Hail can actually cause a lot of damage especially to cars and vehicles, aircrafts, buildings, crops and animals. More often than not, it is the roofs which take full effects of the hailstorm damage and can cause cracks in buildings and leaks in the roof. Hailstorms are very troublesome to drivers of vehicles because they can reign down on vehicles and cause a lot of damage to roofs, hoods and even come crashing through sunroofs. Windshields are often the target of hailstones and can crack or shatter them completely.

Why does the sky look green during some hail storms?

Scientists don’t agree on why the sky may appear green during severe weather, although there is plenty of anecdotal evidence that it can mean hail may be nearby. One theory is that large amounts of water and ice in a severe thunderstorm will scatter green light during the strong updrafts that occur in severe storms.