Hailstorm Hits New England, But How Do These Rocks Form?

Hail is a form of precipitation that occurs primarily in summer. It forms when raindrops are drawn high enough into a thundercloud in the cold areas of the upper atmosphere, then accumulate supercooled water, which in turn freezes. The more water, the larger the hail.

Huge hailstones measuring 4 to 5 inches wide, about the size of a grapefruit and a CD, have been known to fall in parts of the Midwest and Great Plains.

Why do some storms produce large hail while others don’t?

The answer lies in the strength and speed of the updraft, or rather the column of air that rises. A thunderstorm has many elements, and the most robust types of thunderstorms, called supercell storms, can not only produce hail but are also responsible for most tornadoes in the United States.

The updraft can be so powerful—reaching wind speeds of over 100 mph—that it can create a rainless zone because raindrops cannot reach the ground; they are instead blown skyward.

There is a lot of activity in the upper regions of a thunderstorm. Supercooled water, which is actually liquid water at less than 32 degrees, water and chunks of ice are colliding.

Depending on the strength of the updraft, hailstones can continue to grow and reach sizes that are not only damaging, but deadly in the most powerful storms.

Note below the strength of the updrafts in some storms. It is no wonder that a raindrop can be carried so high to form this most interesting type of precipitation. Wind speeds range from 24 mph to produce pea-sized hail to 98 to 103 mph for grapefruit- and softball-sized hail, respectively.

Depending on the temperature of the upper atmosphere, storms can create cloudy or clear hail. If the ice forms quickly, the air bubbles remain intact, resulting in cloudy ice called “dry growth.” Supercooled water that spreads over a small ice core and freezes more slowly allows the air bubbles to escape, leaving the ice clear: this is “wet growth” hail.

Hail in New England

Our thunderstorms, even the largest ones, generally do not develop the type of structure conducive to sustained updrafts with enough speed to generate the largest hailstones.

Additionally, unlike some more mountainous areas of the country, the distance between the ground and the freezing level during the summer when thunderstorms occur is much greater, meaning hail has plenty of time to melt before reaching the ground.

Which states experience the most hail?

Although Florida is the state with the most thunderstorms in the United States, places like New Mexico, Colorado, and Wyoming experience the most hailstorms because the frost layer is closer to the ground, while in Florida the frost layer is very high, making it more difficult for hail to form.