Courtney's Cloud Corner: Forming Precipitation | weatherology°
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By: Meteorologist Courtney Steimann
Updated: Feb 25th 2019

Courtney's Cloud Corner: Forming Precipitation

How does precipitation form in clouds?

Well, there are two types processes that deal with warm clouds and cold clouds forming precipitation, the warm clouds process and the cold cloud process. The warm cloud process works with the collision and coalescence process with only liquid water. It’s the growth process of water droplets as smaller droplet collide with other smaller droplets to create a bigger droplet. The droplet will grown in size which will cause it to drop from the cloud. For example, if you looked at a window with raindrops on it, you can see some of the droplets are attaching to others and growing. This results in them getting heavy enough to fall down the window.

The cold cloud process deals with both liquid water, ice crystals, and supercooled water. Supercooled water occurs when the atmosphere at or below the freezing point (32 degrees Fahrenheit) and still remains in its liquid form. When in a cold cloud, there is a difference between the water vapor pressure. The ice crystal will then grow in size and gain enough weight to fall. Even if the cloud forms and drops ice crystals, they may still appear as raindrops on the ground. This can occur if the temperature is above freezing and stays above freezing the whole time the droplet falls.

Different size water droplets.
Different size water droplets that can attach and grow large enough to fall. This can be done through the warm cloud process.
Different size snowflakes.
Different size snowflakes formed from the cold cloud process.