Clouds are such a common part of our everyday lives that we rarely pause to consider the different types and what this can tell us about the weather. By studying the local clouds you can begin to make short and long term forecasts of your own.
Most clouds are identified and named using 5 Latin words. When combined, these words describe the cloud characteristics and the height of the cloud in the sky. These 5 words form the basis for the most common cloud types:
Cumulus: lumpy, fluffy, heaped cotton ball clouds
Stratus: layer, flat, pancake clouds
Cirrus: wispy, curly, high clouds
Nimbus: rain clouds
Alto: refers to clouds of medium height in the sky
Compounding these simple words enables you to more accurately describe almost any type of cloud in the sky. For example, a medium level, fluffy cloud is an altocumulus cloud, and a low, flat rain cloud is a nimbostratus cloud.
Not only do the names of clouds tell you about the cloud's characteristics, but they can actually tell you something about what weather you can expect in the future. A general rule to follow is that increasing clouds that become lower in the sky indicate bad weather on the way. Additionally, clouds that begin to develop vertically (clouds that become higher and higher) indicate a good chance of heavy rain and possibly severe weather. Listed below are some of the most common cloud types and what they can tell you about the weather.
These clouds occur over 20,000 feet in the sky and are made of ice crystals.
Cirrus - Cirrus clouds are high, wispy clouds made of ice crystals. Often called 'mare's tales,' these clouds follow the dominant wind direction, meaning that in the US, they usually blow from west to east. Cirrus clouds (especially when they appear to be lowering and increasing in size) may be a warning that a warm front and rainy weather is approaching.
Cirrocumulus - These fluffy clouds are very high, and appear very small. Cirrocumulus rarely cover the entire sky and may mean that precipitation will occur shortly.
Cirrostratus -These high sheet-like clouds are often so transparent that they only appear as a film over the sky. They are usually most visible by the halo they form around the sun or the moon. This can mean lowering clouds and precipitation in 48 hours.
These clouds occur between 6,500 and 20,000 feet and are made of both cloud droplets and ice crystals.
Altocumulus - These mid-level, medium sized, fluffy clouds are between cirrocumulus and cumulus clouds in both height and size. When these appear in the morning they may be a warning of thunderstorms in the afternoon (within 24 - 48 hours).
Altostratus - these clouds are thicker and lower then cirrostratus and don't have a halo. When these clouds become darker it may mean precipitation within 48 hours.
These clouds occur below 6,500 feet and are made mostly of cloud droplets.
Stratus - These are low, flat clouds. Technically, fog is a type of stratus cloud. These clouds do not allow much sun to pass and thus the ground often remains cool.
Nimbostratus - These are basically stratus clouds that are raining and appear a dark color in the sky.
Vertically developed clouds
These are the tall clouds and can extend into the sky over 39,000 feet.
Cumulus - Cumulus clouds are fluffy, or heaped clouds that often occur during the afternoon in the summer. These clouds get taller when the air is more unstable. In general, these clouds mean fair weather, however, when they grow taller and closer together, they can indicate thunderstorms.
Cumulonimbus - These are the big ones. These massive clouds stretch high into the sky and are thunderstorms. These storms often produce severe weather and should be taken seriously.
You are now on your way to making your own forecasts! Once you get the hang of these basic clouds and begin to become familiar with the different patterns in your own area you may find you have just as much luck making forecasts as the professionals!