Clouds form when water evaporates off of oceans, seas, rivers, lakes and ponds, and then condenses in the atmosphere. The names of cloud types are determined by how they form and what they look like to someone on the ground.
In basic terms, cloud classification can be summed up in to three height levels for clouds and five description terms that rely on Latin words. The classification looks like:Height Level Name Altitude High-level clouds 20,000 feet and above Mid-level clouds 6,500 to 20,000 feet Low-level clouds Below 6,500 feet Descriptive Names Latin Root Translation Cumulus “Heap” Stratus “Layer” Cirrus “Curl of Hair” Nimbus “Rain” Alto “Mid” or “Middle”
The Highest CloudsHigh-level clouds are primarily made of ice because they are formed at such high, and thus very cold, elevations. These clouds are often very thin and look starkly white during the day. When the sun is rising or setting, however, they will refract light in the atmosphere and can be adorned in a multitude of blues, purples, pinks, and reds.
Cloud types in this range include the cirrostratus, cirrus, and cirrocumulus. These clouds tend to stretch over long areas when they form.
Cirrus clouds are wispy and often look feather-like. Meteorologists use these clouds as indicators of warm fronts moving through an area.
Cirrostratus clouds look like a ribbed blanket or veil covering the sky. These clouds are known for creating a ring around the Sun or Moon when they lie in front of it. Their ice crystals refract light very well.
Cirrocumulus clouds usually form in layers with a lumpy or bumpy look. They often look like pieces of cotton tossed high in the sky but sometimes can form as large bumpy sheets.Middle-elevation Clouds The mid-level group of clouds is often made of a mixture of ice crystals and water droplets, though they usually have more droplets in the mix. In winter months, these clouds often do not contain snow except at lower elevations.
Clouds in this range include the altostratus and altocumulus clouds.
Altostratus clouds usually appear flat and uniform in shape, with the viewer being able to see sky above them clearly. These clouds usually enter areas when a warm front approaches and can thicken with water and fall into lower elevations to become rain and snow clouds.
Altocumulus clouds look like a low-sitting blanket with clumpy parts and show that two different air zones may be colliding.
Low-flying CloudsLow-level clouds are your water-based clouds and often your rain clouds. When the weather gets cold, these are also the clouds that bring icy rain, sleet, and snow to your front door. The nimbostratus and some stratocumulus clouds are the most common cloud types in this region.
Stratocumulus clouds are clumpy layered clouds that seem to go as high up as they do spread across. They are very common and usually show up in the sky before or after a front moves in. Nimbostratus clouds are those that seem to blanket the entire sky at points and are often the clouds that create steady, heavy rain and snow. They are very long and can be short on sunny days.
Clouds are created by the accumulation of water vapor and ice in the atmosphere. Different names are given to clouds depending on what the clouds are made of, where they are located, and how they look.
The appearance-based naming aspect is relative to their observation by someone on the ground, not anything in the air.
Cloud names and types follow a basic structure of elevation groupings plus names based on descriptive Latin Words.
The height groupings are:
- High-level clouds that appear at 20,000 feet and above;
- Mid-level clouds located between 6,500 and 20,000 feet high; and
- Low-level clouds that form below 6,500 feet.
- Cumulus, which means “Heap;”
- Stratus, which means “Layer;”
- Cirrus, which means “Curl of Hair;”
- Nimbus, which means “Rain;” and
- Alto, which means “Mid” or “Middle.”
High-level cloudsClouds formed at this elevation are made mostly of ice and tend to be thin and long. These clouds are most commonly of the cirrus, cirrostratus, and cirrocumulus types.
Cirrus clouds are thin and wispy, signaling that a warm front is on its way. Cirrostratus clouds are blanket-like and thin. Because they are so high and icy, they often will create a ring or halo look around the Sun or Moon. Cirrocumulus clouds are large and bumpy, but very high. Cirrocumulus often show areas of the sky where clouds will ascend or descend.
Mid-level CloudsClouds in this middle elevation range are a mix of ice and water, though they do not rain or sleet from this elevation. Most clouds are more water than ice. The two most common types of mid-level clouds are the altostratus and altocumulus.
Altostratus clouds are very flat looking and smooth, with a uniform shape and a movement that impacts the entire formation. These clouds often enter ahead of a warm front. If the front stalls or meets another one, they can grow and turn in to rain clouds as they absorb water and descend.
Altocumulus clouds also have a large, uniform shape, but instead of being smooth they look like blankets with bumps and ridges. These clouds often form when two air fronts collide and they signal the potential for storms to occur.
Low-level CloudsThe lowest clouds are the ones that often become storm clouds for both rain and snow. These clouds are fluffier than the rest and are most commonly the nimbostratus and some stratocumulus clouds.
Nimbostratus clouds appear to cover the entirety of the sky and often signify a prolonged rain or snow storm. These clouds can last for a long time after a storm because they form when there is little atmospheric movement. Stratocumulus clouds are clumpy clouds that have many layers vertically and horizontally. They show up and move swiftly in the sky as fronts arrive and leave.