6. Stratus - Flat layered clouds, usually dull grey, which cover
most of the sky, even blocking out the sun. They begin as a bank of
fog that has risen higher than ground level.
7. Nimbostratus - 'Stratus' meaning broad layers covering the
whole sky, and 'Nimbo' meaning that they are producing steady, long
lasting, though not heavy, rain that covers a broad area. They are
dark grey clouds that usually mean a dull day and possibly rain.
They completely block out the sun.
8. Cumulus - Meaning puffy and heaped.
9. Stratocumulus - Meaning they are basically a flat sheet of
clouds covering most, if not all of the sky, but "cumulus'
meaning that the layer is somewhat puffy.
10. Cumulonimbus - 'Cumulo' meaning puffy, and 'nimbus' meaning
there is precipitation falling from them. Characterized by dark
bases and puffy tops, heavy rain, and thunder and lightening.
Any low altitude clouds that are dark, threatening rain or
producing rain get the designation 'nimbus' or 'nimbo'.
Cumulus and Cumulonimbus clouds have a base that starts at less
than 2000 metres, but often grow tall enough to reach into the middle
and sometimes high ranges. Only cirrus-type clouds are true high
altitude clouds. They a base starting above 6000 meters.
Extended Notes About Cloud Shapes:
Cumulus means a heap or pile in Latin. These are white puffy
clouds that look like giant bunches of cauliflower with flat bottoms.
They are seen mainly in the summer on warm, sunny days. The sun warms
the ground and huge bubbles of heated air rise into the sky. As with
other clouds, the air cools, condenses, and in this case forms a cloud
that is big and fluffy looking due to the cloud being formed with
liquid versus ice crystals.
Cumulus clouds reflect sunlight well because of the water droplets
and they look very white. They are darker on the bottom because the
sunlight gets filtered out more and more as it passes through these
thick clouds, especially when they are at their largest. We generally
don't see these in winter because it is too cold for the droplets to
Cirrus means a curl or a tuft of hair (wispy) in Latin.
These are feathery, wispy clouds with curled tails, like a horse's
tail blowing in the wind. These are high-altitude clouds made the same
way that all clouds form, but the water droplets are frozen to form
millions of tiny ice crystals. They are often the first clouds to
appear in a clear, blue sky.
Stratus means a flat layer or 'stretched out' in Latin.
These are dull grey clouds. They cover most of the sky and block out
direct views of the sun. They often start as a bank of fog (low dense
cloud) that rises higher in the sky.
How Do Clouds Form?
Clouds occur at weather fronts. Weather fronts occur where warm and
cold air masses meet.
Warm air is pushed higher and as it rises and cools, this causes
condensation, which forms clouds. Clouds, mist and fog are made of
millions of water droplets of condensing moisture from the air. They
can also be made of tiny ice crystals that form as a result of the
cooling process happening more quickly, or to lower surrounding
Rain and snow, as well as freezing rain and hail are variations of
the precipitation that falls from clouds depending on the conditions
in which they form. The conditions are influenced by the geographic
location, weather fronts, climate, season of the year, amount of
moisture in the air that results in the daily temperature, and the
occurrence, amount, and form of precipitation.
Fog is a cloud up close. It forms close to the ground as a result
of air currents and fronts. A cloud is exactly the same as the white
puffs of air that we see when we breathe outside on a cold day. The
warm air from our lungs contacts the cold air and condenses into water
droplets, forming the visible white cloud of condensed air. The same
is true of water vapor (the gas form of water once heated to the
boiling point) as it escapes a pot of boiling water. The air in the
room is cooler than the temperature in the pot and as the warm vapor
hits the cooler air, it cools, condenses and forms what we call steam,
which is a cloud.
The most important factor that must exist to form a cloud is the
amount of moisture in the atmosphere. If there is not enough water in
the atmosphere then there can be no condensation into tiny droplets
that form clouds. The water in the atmosphere comes from oceans, lakes
and plants through the water cycle. Water in lakes and oceans
evaporates, just as water left in a bowl for a period of time will
eventually disappear. Water that plants draw up through their roots
eventually evaporates through the leaves of the plants.
It evaporates, rising as a gas into the atmosphere, but condensing
as it begins to cool in higher altitudes to form clouds. The water
droplets grow larger as more warm air condenses and eventually become
too heavy to continue rising or to be held up by the rising warm air.
At this point the water droplets fall in the form of precipitation.
Forms of Precipitation
Water is part of a cycle called the Water Cycle. As water evaporates
from the various bodies of water, plants, and animals, it rises into
the atmosphere. There, some of the water rises high enough to cool at
the higher altitude, which causes the water vapor to condense into
tiny water droplets that form clouds. Some clouds produce
precipitation, during which the water that forms the clouds falls back
to the earth.
Precipitation is in different forms depending on the altitude of
the cloud. The altitude affects the temperature in the atmosphere and
therefore the form of the water droplets that form the clouds. Another
influence on the type of precipitation that forms is whether there are
strong upward drafts of air inside the cloud.
Rain is a water droplet in liquid form, usually in lower
Snow falls when clouds are in higher and colder altitudes,
which causes the water vapor to freeze as it condenses to form ice
crystals instead of water droplets that form the cloud.
Sleet is rain that freezes as it is falling in cold
Freezing Rain is rain that freezes when it contacts the
Hail forms inside tall clouds with air currents blowing the
water droplets up and down. Rain starts to fall inside the cloud, but
it is caught by an upward sweeping wind and forced into a higher
altitude. The drop of rain freezes in the higher altitude and falls,
forming more condensation on it. It can be swept up again to refreeze,
forming a larger hailstone. The size of the hailstone depends on the
number of times this cycle repeats, which depends on the strength of
the upward draft of wind in the cloud.