system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can hail stay in the air before falling down, and how can it be big sometimes but small others?
gpt
In the upper atmosphere, air can tumble like a high-speed clothes dryer. Some very cold air falls in parts of the cell usually while relatively hot air funnels up toward the top. These winds go at such high speeds that the wind lifts a falling water droplet back toward the cold top of the system where it freezes.

This frozen droplet then falls, catches the wind, and is flung to the top of the system again. As this droplet continues to tumble, it runs into other droplets which freeze to its surface.

The stronger and higher winds are in the system, the heavier of a piece of ice it will be able to lift back to the top of the system leading to bigger and bigger pieces of hail as it keeps getting coated in water and freezing it. If it's not a super strong system, then the ice gets too heavy for the tumbling wind to carry much sooner and the ice falls as smaller hail.