Clouds are segregated into 4 categories: High clouds, Mid-level clouds, Low clouds, and special clouds. Each category is defined by how high the cloud is floating, and is then further segregated into sub-categories depending on their shape. Cirrus Clouds — Thin, wispy, and delicate, these feather-like clouds are mostly made up of small ice crystals spread across a large area.
Cirrus clouds are the kind of clouds you see on an almost-clear day, and while they can be pleasant to look at, they are also harbingers for a change in weather: their appearance comes from the wind currents that spread them out into their shape.
Cirrostratus Clouds — Similar to cirrus clouds, cirrostratus clouds are also wispy; but rather than long, thin strands, cirrostratus clouds cover the sky in a thin veil.
Usually encountered during winter, cirrostratus clouds also cause halos to appear around the sun and the moon, not to mention cause the appearance of partial or complete halo phenomena around the sun or the moon.
Be careful though: cirrostratus clouds are almost always followed by rain or snow a day after. Cirrocumulus Clouds — small, thin, patchy, puffy, and sheet-like, cirrocumulus clouds often look like ripples in the sky, giving it a grainy looking texture. In temperate climates, this often indicates cold, but fair, weather; in tropical countries, however, this could indicate the coming of a hurricane.
Altocumulus Clouds — Altocumulus clouds are small, mid-level clouds that are made up of smaller patches of clouds called cloudlets. These cloudlets usually appear like rounded clumps and can be made up of several layers of grey and white.
Altocumulus clouds are often signs of fair weather. These clouds are most commonly seen in the winter, and can cause the appearance of a halo around the sun or the moon. Weather prediction: Rain or snow will arrive within 24 hours!
Cirrocumulus clouds are thin, sometimes patchy, sheet-like clouds. Weather prediction: Fair, but cold. However, if you live in a tropical region, these clouds could be a sign of an approaching hurricane! Altocumulus clouds have several patchy white or gray layers, and seem to be made up of many small rows of fluffy ripples. They are lower than cirrus clouds, but still quite high. Weather prediction: Fair. Altostratus clouds are gray or blue-gray mid-level clouds composed of ice crystals and water droplets.
The clouds usually cover the entire sky. Weather prediction: Be prepared for continuous rain or snow! Nimbostratus clouds are dark, gray clouds that seem to fade into falling rain or snow.
They are so thick that they often blot out the sunlight. Weather prediction: Gloomy with continuous rain or snow. The lowering clouds indicate that the front is drawing near, giving a period of rain in the next 12 hours. Stratus is a low continuous cloud sheet covering the sky.
Stratus forms by gently rising air, or by a mild wind bringing moist air over a cold land or sea surface. Stratus cloud is thin, so while conditions may feel gloomy, rain is unlikely, and at most will be a light drizzle. Our final two cloud types will not help you predict the coming weather, but they do give a glimpse of the extraordinarily complicated motions of the atmosphere.
Smooth, lens-shaped Lenticular clouds form as air is blown up and over a mountain range. Once past the mountain, the air sinks back to its previous level.
As it sinks, it warms and the cloud evaporates. But it can overshoot, in which case the air mass bobs back up allowing another Lenticular cloud to form. This can lead to a string of clouds, extending some way beyond the mountain range. The interaction of wind with mountains and other surface features is one of the many details that have to be represented in computer simulators to get accurate predictions of the weather.
And lastly, my personal favourite. Above: Cirrus clouds on a beautiful day Courtesy geograph. Now we reach the clouds that are sometimes at the center of controversy, contrails. No, they are not formed as a result of chemicals emitted into the atmosphere, but mainly because of the water vapor released by the exhaust of an aircraft.
When the aircraft releases the hot water vapor at such a high altitude, it becomes trapped in a very cold environment where it almost immediately condenses and forms a cloud.
Depending on how dry the upper atmosphere is, the contrail cloud may stick around for mere seconds or spread out and become cirrus clouds for hours. However, these clouds are not associated with any weather. The lenticular cloud is one of the more unusual cloud types and is more common to those living out west, especially in the Rocky Mountains.
This cloud resembles a lens and is typically positioned over a high hill or mountain. As the wind blows against the mountains, it is forced upward and moisture condenses, forming a cloud that stays stationary until the uplift or moisture feed ends. Although these clouds could produce precipitation if dense enough, they are mainly an indicator of air turbulence downstream.
However, due to their unique shape, many times they have been mistaken for UFO sightings! Finally, we have mammatus clouds. These almost look like little pouches or bubbles of cloud hanging from the above cloud deck.
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