Clouds are collective masses of either water droplets or crystals of ice. Clouds are a near ever present companion to the sky lines, sometimes molding themselves into abstract shapes or amassing in a great mass of gray and black warning of storms. Due to the many different shapes and sizes of clouds they have be classified into a variety of different types of clouds.
While there are a great many of subcategories, clouds are organized into three primary groups based on their location in the sky—High level, medium level, and low level. The high level being the highest in the sky and the lowest being the closest to Earth, obviously.
High Level Clouds
Cirrus clouds are found high in the sky at around 16,500 feet. Due to this high altitude, the water that makes up lower clouds freezes into ice crystals. This clouds are near transparent and very wispy. They often tend to near blend into the sky as they are so high up. Some may think that these mean pretty stable weather, however they are often a sign of a gathering storm.
Below the cirrus at around 16,000 feet, the clouds become known as Cirrocumulus. Like the Cirrus, they are also made up of ice crystals. However, the Cirrocumulus is fairly rare. They are essentially just little clouds evenly spaced apart that create a rippling veil layer over the sky. Consider yourself lucky if you see them as they are a marvelous sight. These are often confused with Altocumulus as they look much the same, but Altocumulus are lower in the sky.
Medium Level Clouds
These clouds appear much like Cirrocumulus in shape. They appear as a rippling veil in the sky, however they are lower in the atmosphere. However, instead of a bunch of little clouds being separately spaced, these clouds are actually connected and thicker as the atmosphere is slightly warmer at their level. These clouds on warm humid days can usually indicate the onset of a coming storm.
These bluish or gray clouds can be composed of both water droplets and ice crystals depending on the temperature. They have kind of found the nice middle point in which water turns to ice. They are thick and wavy in pattern due to the wind constantly being blown through them. They are responsible for those lazy overcast days where you can still see the sun, but everything looks darker. They can occasionally produce slight precipitation.
These are the big thick rain clouds that everyone is familiar with. They are thick and gray and block out the sun. Whereas Altostratus produce overcast days where you can see the sun through them, these produce rainy days. Though usually, they are accompanies by Altostratus on days where the rain is spotty. Depending on the temperature, these clouds can also produce snow. However, while they can produce snow and rain, they cannot produce any kind of lightening or thunder.
Low Level Clouds
These clouds cover the sky in a thick sheet and do not form vertically like some other low level clouds. These clouds can also sink close to the ground in the form of fog or mist before evaporating in the sun. While these formations are thick and have little transparency, the sun or moon can be seen through them if there are no other formations in the higher levels of the sky. On occasion, these clouds can be responsible for light drizzle and flurries.
These clouds are present in the sky during all sort of weather. They do not produce precipitation. They share certain similarities to the Altostratus and the Cirrostratus clouds as they can often look rippled. However, the cloud is one big thick layer.
These are perhaps the most famous formations, especially for the leisurely activity of cloud watching. They form vertically upwards giving them a tall looking shape. Most frequently, they look like big heaps of cauliflower in the sky, allowing for people to see many abstract shapes in them. While they can have a dark appearance on the bottom indicating rain, they are more often a sign of fair weather. However, if they get big enough in size, they can produce rain showers. Because of the heights they can reach, they can be made up of water droplets and ice crystals, however they are primarily water.
These clouds are famous for looking huge, similar to the Cumulus but taller and frequently one giant mass. These are the types of clouds that are responsible for producing thunderstorms. They are extremely dense and heavy, often making them signs of a coming heavy rain storm. Because of their high, water droplets can often get swept up into colder regions of the sky and produce hailstorms as well. When the winds cause the cloud to vortex, it can also produce tornados. So they next storm with heavy rains, thunder, and a potential for tornadoes, you are staring at big old Cumulonimbus.
Kelvin Helmholtz Clouds
These are more commonly known as billow clouds. They are an extremely rare sort of cloud occurrence in which two different air currents clash at different speeds and the clouds get caught in their wake. If you see these, it means there is some instability in the atmosphere due to various causes.
These wedge shaped clouds are caused by rain chilled air dropping to the ground and spreading laterally. SThis formation is a very ominous sight indeed as they are a precursor to some of the most fierce thunder storms. If you see one, snap a picture and be ready to spring into the storm shelter, they are a precursor to bad weather and can often signify a storm with heavy potential to produce a tornado.
These are perhaps the rarest of formations. Lenticular clouds adopt the guise of a saucer in the sky. Because of this, I am sure some have mistaken it for a UFO. These formations occurs at very high altitudes, usually around mountainous regions due to the varied air flow.