why does hailstones have layers in the morning?

The Deep Dive

Hailstones form within the intense updrafts of cumulonimbus clouds, commonly known as thunderstorms. The process begins with a tiny ice crystal or frozen raindrop, called an embryo, suspended high in the cloud. Powerful updrafts, which can reach speeds of over 100 miles per hour, lift this embryo into regions of the cloud where supercooled water droplets exist. These droplets remain liquid below freezing temperatures. As the embryo collides with these supercooled droplets, they instantly freeze onto its surface. If the freezing is slow, often occurring in warmer parts of the cloud or when the hailstone is briefly suspended, air bubbles escape, forming clear ice. If the freezing is rapid, typically in colder regions or during fast accretion, air gets trapped, creating an opaque, milky layer. The hailstone may then become too heavy for the updraft, falling into the lower parts of the cloud, sometimes partially melting, before being caught by another updraft and lifted again. This cycle of being lifted, accreting ice, and falling can repeat multiple times, with each trip through different temperature and moisture zones adding a new layer of clear or opaque ice, much like the rings of a tree. Eventually, the hailstone becomes too heavy for even the strongest updrafts and falls to the ground.

Why It Matters

Studying the layered structure of hailstones provides invaluable insights into the dynamics of severe thunderstorms. Meteorologists can analyze the number, thickness, and composition of these layers to reconstruct the internal conditions of the storm, including updraft strength, temperature profiles, and the amount of supercooled water present. This information helps improve our understanding of storm development and intensity, leading to more accurate forecasts and warnings for severe weather events like damaging hail. Furthermore, understanding hail formation is crucial for agriculture, as hail can devastate crops, and for aviation, where hailstones pose significant hazards to aircraft. Research into hail suppression techniques also benefits from this detailed knowledge.

Common Misconceptions

A common misconception is that all hailstones are perfectly spherical. In reality, hailstones often have irregular shapes, including jagged edges and lobes, due to their chaotic journey through the storm and the way ice accretes unevenly. Another myth is that larger hailstones always indicate a stronger updraft. While strong updrafts are necessary for large hail, the duration of the hailstone's journey within the storm and the abundance of supercooled water are equally critical factors. A hailstone needs sufficient time to grow and enough liquid water to accrete multiple layers, regardless of the maximum updraft speed it encounters.

Fun Facts

• The largest hailstone ever officially recorded in the United States fell in Vivian, South Dakota, on July 23, 2010, measuring 8 inches in diameter and weighing nearly 2 pounds.
• Hailstones can fall at speeds exceeding 100 miles per hour, making them incredibly dangerous projectiles.