1. Formation: Hailstones begin as tiny ice crystals, similar to snowflakes, in the upper regions of thunderstorms. These clouds contain supercooled water droplets, which are liquid water below freezing point (0°C or 32°F).
2. Upward Drafts: Strong updrafts within the storm lift the ice crystals higher into the cloud. As they ascend, they encounter more supercooled water droplets.
3. Accretion: The ice crystals collide with the supercooled water droplets, which freeze onto the crystal's surface, causing it to grow. This process is called accretion.
4. Layer Formation: As the hailstones continue to rise and fall within the cloud, they can experience different temperature and humidity conditions. This leads to the formation of layers of ice with varying densities, creating the distinctive layered appearance of some hailstones.
5. Growth Cycle: This process of accretion and layering continues as the hailstone cycles through the storm, growing larger with each trip. The size of the hailstone depends on factors such as the strength of the updrafts, the amount of supercooled water, and the duration of the storm.
6. Falling Out: Eventually, the hailstones become too heavy to be supported by the updrafts and fall to the ground.
Here's a simple analogy: Imagine a snowball rolling down a hill, collecting more snow as it goes. Hailstones work similarly, but instead of snow, they collect supercooled water droplets.
Factors Influencing Hailstone Size:
* Updraft Strength: Stronger updrafts lead to larger hailstones as they allow for more time to accrete ice.
* Supercooled Water Content: Higher concentrations of supercooled water result in faster growth.
* Storm Duration: Longer storms allow for more time for the hailstone to grow.
Note: The entire process of hailstone formation can be quite complex and involves numerous meteorological factors. However, the basic principle of accretion and upward drafts remains crucial for understanding how these icy pellets grow.
