Distinguish the Different Types of Clouds

Cloud watching or observing is for dreamers, scientists, nature lovers, and you. While it may be tempting to refer to those big fluffy things as "heavy, rain-sodden or dark," if you're interested in cloud classification, it's fun (and useful) to know the terminology. First invented by the English scientist Luke Howard, the classification for clouds is divided by their height: low, middle and high altitudes, their shape: cumulus and stratus, and by the weather they bring with them.

Steps

  1. Become more familiar with the clouds. There are many different types of clouds, and clouds are a great "collectible" for record-keeping. Cloud knowledge is fun for dinner party chats, and, for some people pursuing activities like hiking or boating that can be dangerous if the weather turns sour, cloud knowledge is vital for survival. Reading cloud shapes can help you to determine the weather headed your way without having to use additional instruments.
    • The shape of clouds will tell you a lot about the stability of the atmosphere.
    • The height of the clouds will tell you the distance of any approaching storm.
    • Shape and height of clouds together will tell you the likelihood of precipitation (rain/snow/hail).
    • Fun facts: Some UFO sightings are actually the result of cloud shapes. Lenticular (lens-shaped) clouds in particular are typically associated with warm fronts on the lee side of mountain ranges.
  2. If you enjoy outdoor activities, take time to learn to tell the weather from clouds. While this article isn't specifically about forecasting, it's helpful to know that the seasoned outdoors person can tell what each type of cloud means for the weather. Different types of clouds form along warm fronts and cold fronts, and a field forecaster should be able to tell what weather is coming by reading the cloud shapes and height. For more information, read How to forecast the weather using clouds.

Cloud shapes

  1. Identify clouds by shape. The two shapes are cumulus and stratus:
    • Cumulus clouds: These are the big, "fluffy" clouds that look a bit like cotton balls. These clouds have a thickness that is usually equal to or greater than their width and they have very distinct edges. Cumulus clouds tend to indicate that the atmosphere is unstable at the altitude where they are found.
    • Stratus clouds: These clouds are layered and often look flat. They're usually much wider horizontally than vertically. Stratus clouds typically indicate a stable atmosphere but can also herald the onset of a non-violent storm. When fog appears it is usually accompanied by stratus clouds.

High altitude clouds

  1. Look for high altitude clouds (also known simply as "high clouds"). These are considered to be clouds that are between 19,500 feet (5,943 meters) and 42,500 feet (12,954 meters). This encompasses cirrus, cirrostratus and cirrocumulus clouds. These clouds tend to be frozen (filled with ice crystals) and have blurry outlines; they are generally thin and wispy to the human eye.
    • Contrails from jet airplanes are also found at this level in the Earth's atmosphere.
    • High clouds produce beautiful red, orange and yellow colors in the sky at sunrise and sunset.
    • Rings of light around the moon or the sun are caused by cirrus clouds. A halo around the sun or moon can suggest rain or snow on the way, especially if accompanied by thickening lower clouds.
    • Cirrus clouds often partially obscure the sun.
  2. Know your cirrus cloud. Cirrus clouds are distinguishable by their thin, white and wispy appearance. They generally reach an altitude above 20,000 feet (6,000 meters). The thinness tends to be due to the frigid winds in the upper atmosphere. Cirrus clouds are made up of ice crystals formed by supercooled water droplets.
    • Cirrus clouds that are sparse and stay that way usually show signs of fair weather. When cirrus clouds change into cirrostratus clouds, wind and precipitation are probably on their way within the next 24-36 hours. Cirrus indicates moisture above; if cirrus changes to altostratus and then stratus, a storm approaches soon.
    • You'll see cirrus clouds as a warm front advances.
    • The direction in which cirrus clouds move will usually tell you the direction of air movement, namely the weather coming your way.
    • Cirrus clouds are sometimes referred to as horse's or mare's tails because they curl out like a horse's tail.
  3. Spot a cirrocumulus cloud. These clouds are often found in rows and they look like little puffed-up ripples. Some people think these clouds look like fish scales. The broken or rippled nature of these clouds is caused by air turbulence; it's bad news for anyone flying through them, but great news on the ground because these clouds usually mean that the weather is going to stay the same with no major sudden changes.
  4. Look for cirrostratus clouds. These clouds tend to lack shape and have a hazy appearance. They usually spread across much of the sky. They suggest moisture is present in a large part of the sky, indicating that rain might be due soon. Thicker cirrostratus clouds can come from the top of an advancing storm system.
  5. Learn how to tell the difference between cirrus clouds and cirrostratus clouds. Cirrostratus clouds are made up of ice crystals as well, but unlike cirrus clouds they can cover the entire sky and be up to several-thousand feet thick. Cirrostratus clouds are sheetlike and nearly transparent.
  6. Watch for contrails. Although these are machine made by jet airplanes, contrails can help you to know the weather in the heights above. Contrails are condensation, formed when the jet's warm exhaust mixes with the very cool air surrounding the jet in the upper atmosphere.
    • If the contrail disappears quickly, or you see a jet with no contrail, this means that the upper atmosphere you're observing is dry. On a lovely day, you can usually take this as a sign that the weather is going to remain fine for a while.
    • On the other hand, if the contrail is obvious for a time, is long and spreads, the upper atmosphere you're observing is wet. Grab your coat and umbrella because the weather will probably change soon, if it hasn't already.

Mid-level clouds

  1. Get acquainted with middle or mid-level altitude clouds. These clouds usually have a height between 6,500 feet and 19,500 feet (1,981 meters and 5,943 meters). They are prefaced with the prefix "alto," and are known as either altocumulus or altostratus clouds. They tend to be less defined than lower clouds, although warmer middle clouds will display sharp edges due to water content, and colder middle clouds will show distinct edges shaped by ice crystals.
    • Scattered middle clouds against a blue sky indicate continued fair weather, and are often succeeded by clear skies and a high pressure system.
    • Altostratus clouds that are becoming lower and have southerly winds in the northern hemisphere (vice versa for the southern hemisphere) can indicate an oncoming storm, but this will usually be several hours away.
  2. Discover altocumulus clouds. Altocumulus clouds are the clouds that you usually see during summer days. They come in many small clouds that are spread across the sky. Altocumulus clouds form by convection (vertical atmospheric motions) and cold fronts. Altocumulus clouds usually are followed by warm and humid summer mornings then a thunderstorm in the afternoon.
    • You can tell the difference between altocumulus clouds and high level clouds by noting the shading. Altocumulus clouds usually have shading underneath portions of the clouds.
  3. Look for altostratus clouds. This middle cloud isn't very exciting––it tends to be grayish and sheet-like without shape. You might spot a glow of the sun behind this cloud. It's a good idea to prepare for wet or snowy weather when this type of cloud crosses the sky.
  4. Look for lenticular clouds around mountain ranges. These lens-shaped clouds or "cloud caps" don't happen everywhere––they tend to only form over mountain ranges and peaks due to the way that winds travel up the slopes. You're probably okay on the ground, but if you're up on the mountain or flying overhead, expect strong winds or turbulence. If you are on a mountain and a cloud cap descends, expect bad weather and seek suitable shelter.

Low-lying clouds

  1. Check out the low clouds. These clouds are usually under 6,500 feet (1,981 meters), and they help to cool the Earth through reflecting back the Sun's heat away from the Earth's surface. They're usually a grayish-blue color and they are often rain clouds because they are filled with water droplets. Early morning low clouds might dry out before they have a chance to rain if the sun is able to evaporate them, which will result in a clear day, but expect rain if this is not the case. In fact, low clouds are the most likely source of rain or snow because their precipitation doesn't have a chance to evaporate before reaching the ground.
    • Rain or snow is fairly guaranteed if you see a lot of low clouds with dark bases. Low clouds of 3,000 feet (914 meters) thickness tend to mean precipitation; since you probably can't guess that height accurately from your observation point, look for the darkness.
  2. Look for nimbostratus clouds. Nimbostratus clouds are dark, low level clouds, followed by light to moderate rainfall, and often continuous in nature. This cloud type frequently forms what looks like a sheet of cloud. Low lying clouds are generally made of water droplets, and can bring snow as well as rain. They're distinguishable from the aforementioned clouds because of their dark, big, and gloomy looking appearance.
  3. Check the skies for the cumulonimbus cloud. This cloud is easily distinguished from other clouds by its massive nature. Cumulonimbus clouds can fill up much of the sky with their massive and puffy pile, making it easy to tell them apart from cirrus or altocumulus clouds. Cumulonimbus clouds are mostly affiliated with thunderstorms, lightning, heavy rainfall, blizzard or hail. They can turn into super cells or tornadoes.
    • This cloud type can look like a big explosion or some see a resemblance to an anvil; the anvil tip points the direction that the weather is moving in.
    • In the event of extreme atmospheric instability, you might see what is known as a towering cumulus cloud. This cloud can have its base as low as a low cloud (6,500 feet) and reach as high as a high cloud. It's a warning sign because it can indicate gusting high winds, lightning, heavy rainfall and hail. In some areas, this cloud can also indicate an oncoming tornado.
    • This cloud brings with it a nasty weather system, but usually it is short lived. The weather following this cloud is often clear.

Tips

  • Cloud color, shape, and size are great ways to tell different cloud types apart.
  • Fog is low-lying cloud. It's thick and wet, and if you're walking through it you might feel it "weighing" heavy upon you in terms of a sensation. Fog can hang around if the winds aren't very strong, especially in areas near large bodies of the water such as the sea or large lakes. When it's windier, or the sun burns off the fog, it can leave quickly.
  • This article doesn't cover all the possible variations of a cloud. If you're interested in more information, check out the International Cloud Atlas, or an online cloud atlas such as the University of Missouri/Columbia (http://weather.missouri.edu/OCA/).

Related Articles

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  • Make a Wind Vane
  • Prepare for a Skywarn Basic Class
  • Make Weather Instruments

Sources and Citations

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