How can hail stay in the air before falling down, and how can it be big sometimes but small others?
In: Earth Science
It starts small, and stays in the air because it’s low weight and wind can blow it upwards. But the longer they stay in wet air under the freezing point the bigger they grow until they can’t be kept up anymore and fall down.
How big they can grow depends on the strength of wind mostly, giant hail only occurs in heavy storms that is able to keep such big objects in the air for long enough
Wind.
In storm clouds there is a strong updraft, that’s what gives thunderstorms that mushroom cloud look. Little ones can be held up for a long time in the updraft, until they grow so large the wind can’t hold them up (or the storm weakens).
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.
The vertical winds in storm clouds can be crazy fast, both up and down, and at top of the cloud it’s cold enough that water freezes. Little seeds of ice form there and fall down. The next wind gust going up carries the small pieces of ice along where another layer freezes onto them. They drop a bit and get blown upwards again, and the hail balls grow layer by layer. Stronger upwards drafts can carry heavier balls of ice, until they’re finally so heavy that they fall out of the cloud.
ETA: It’s funny, we had just this topic earlier today and this is the actual elementary school explanation.
The same way a hurricane can flip over your car. The wind up there can go pretty fast, and hail is basically a raindrop which is blown upwards on a powerful updraft, back to where it’s so cold, the rain freezes into a small pellet. Then if the updraft continues, it stays up there as it attracts and condenses more of the moisture on its surface, like frost on a mug full of a cold beverage. When the updrafts cease to be strong enough to keep the hail aloft, down they come.
There are up draughts in the clouds which push the hail up until gravity overcomes the force lifting it up, the more times the hail goes up and down the cloud the bigger and heavier it gets. https://youtu.be/tNyDxBBAeeg
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