Understanding Size, Formation, and Damage

Hail, a type of solid precipitation that forms within thunderstorm updrafts, has fascinated and intimidated humans for centuries. Frequently causing damage to homes, cars, and aircraft, and posing a significant threat to people and livestock, these formidable ice orbs are a spectacle of nature’s power.

From Raindrop to Hailstone: How Hail Forms

Hailstones take birth when ordinary raindrops are lifted by thunderstorm updrafts into the frosty regions of the atmosphere. Here, they freeze and start their journey of growth, colliding with other liquid water drops that freeze onto their surface. This growth process can result in hailstones having layers of clear and cloudy ice, depending on the conditions they encounter during their ascent.

Interestingly, these layers don’t form due to the hailstone going through up and down cycles within the thunderstorm, contrary to popular belief. Thunderstorm winds are not just vertical; they also have a horizontal component that can significantly influence the hailstone’s trajectory and growth.

Gravity’s Pull: How Hail Falls To The Ground

A hailstone’s descent is all about timing and balance. It falls when it becomes too heavy for the thunderstorm’s updraft to support or if the updraft weakens. Smaller hailstones, due to their lightweight, can be blown away from the updraft by horizontal winds. As such, larger hail tends to fall closer to the updraft than smaller hail.

The speed of falling hailstones depends on a plethora of factors: their size, the friction they encounter with the surrounding air, local wind conditions, and even the degree of their melting. The expected fall speed ranges from 9 mph for small hailstones to over 100 mph for those with diameters exceeding 4 inches.

The Geography of Hail: Where it Strikes the Most

In 2024, the United States once again claimed its title as the hail damage capital, with Nebraska, Colorado, and Wyoming—known as “Hail Alley”—experiencing the most frequent storms. These states endure an average of 7-9 hail days per year, with the 2024 season breaking records for both frequency and severity.

Hailstorms create paths known as hail swaths as the storms move while the hail falls. These swaths can vary from a few acres to an area 10 miles wide and 100 miles long. Some storms churn out a mass of small hail instead of large hailstones, which can create hazardous conditions resembling icy winter roads when covering roadways completely.

Hail Size: From Peas to Grapefruits

According to NOAA National Severe Storms Laboratory, the largest hailstone recovered in the United States fell in Vivian, South Dakota, on June 23, 2010. It had a massive diameter of 8 inches, a circumference of 18.62 inches, and weighed almost 2 pounds. However, hail sizes vary significantly. They’re often compared to everyday objects for easier estimation:

• • • Pea = 1/4 inch diameter
    • Mothball = 1/2 inch diameter
    • Penny = 3/4 inch diameter
    • Nickel = 7/8 inch
    • Quarter = 1 inch (hail this 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
    • Teacup = 3 inches
    • Softball = 4 inches
    • Grapefruit = 4 1/2 inches

In the end, it’s crucial to remember the damage potential of hail and take appropriate safety measures during hailstorms. From car windshields to rooftops and from crop fields to livestock, hail can wreak considerable havoc. Stay informed and stay safe!

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