why does hailstones have layers at night?

The Deep Dive

The layered appearance of hailstones, often referred to as "rings," is a fascinating testament to the dynamic conditions within a thunderstorm. It's not an indicator of nighttime formation, but rather a record of the hailstone's journey through varying atmospheric environments. As a hailstone grows, it's tossed around by powerful updrafts and downdrafts within the cumulonimbus cloud. When it encounters regions of supercooled liquid water (water that remains liquid below freezing), this water freezes rapidly on its surface, creating a layer of clear ice. If the hailstone then gets carried into a drier area of the cloud or a region with fewer supercooled droplets, it may accumulate graupel or soft rime, which are less dense and appear opaque. This process of cycling between wet and dry environments, or between different densities of water accumulation, leads to the alternating layers of clear and opaque ice that we observe when a hailstone is cut in half. The size and thickness of these layers depend on the hailstone's trajectory, the intensity of the updrafts, and the availability of moisture at different altitudes within the storm.

Why It Matters

Understanding hailstone layers helps meteorologists reconstruct the life cycle of a hailstone and the atmospheric conditions that produced it. This information can improve weather models and forecasting, leading to better warnings for severe weather events. Analyzing hailstone layers can also reveal details about the specific storm dynamics, such as the strength of updrafts and the cloud's freezing level. This scientific insight allows us to better predict the size and destructive potential of hail, which can cause billions of dollars in damage to crops, vehicles, and property annually.

Common Misconceptions

A common misconception is that the layers in hailstones are analogous to tree rings, indicating age or seasonal growth, and that they form specifically at night. This is incorrect; hail forms within thunderstorms, which can occur at any time of day or night. The layers are not seasonal but are formed by repeated cycles of growth within the storm cloud. Another myth is that all hailstones have many distinct layers. While some do, the number and clarity of layers vary greatly depending on the storm's intensity and the hailstone's path through different moisture and temperature zones.

Fun Facts

• The largest hailstone ever recorded in the United States was found in Vivian, South Dakota, measuring 8 inches in diameter and weighing 1.94 pounds.
• Hailstones can grow to be the size of a grapefruit or even larger, depending on the strength of the thunderstorm's updraft.