How a Hailstone Records Its Route Through a Storm
A hailstone is built from supercooled water: liquid droplets that remain unfrozen even though they are below freezing. When a growing stone sweeps through these droplets, they strike its surface and can freeze there. What happens next depends on how much liquid arrives and how quickly the stone can lose heat.
Why Some Layers Look Clear and Others Cloudy
If the stone is relatively cool, incoming droplets freeze quickly. Air gets trapped in the ice, making the layer look milky or cloudy. If the surface is warmer and coated with liquid water, freezing takes longer. Air has more time to escape, leaving clearer ice. These different growth conditions can alternate as the hailstone moves through regions with different temperatures and supplies of water.
The contrast is not a perfect marker of altitude or a precise map of the storm. It reflects the conditions at the stone’s surface while each layer formed—especially the balance between water arriving and heat escaping.
The Storm’s Updraft Builds the Layers
A storm’s updraft, a rising current of air, can keep a hailstone aloft while it gathers more droplets. The stone may move through zones where liquid water is abundant and others where it is less available, while its temperature and rate of freezing also change. Each shift can add another band of ice. Eventually, the stone becomes heavy enough to fall out of the updraft and reach the ground.
That is why cutting a hailstone open can reveal more than its size: its alternating bands preserve a small, physical record of changing growth conditions inside the storm.
