Explain types of clouds? – Cirrus, Stratus, and Cumulus

Most of us have fantasized while admiring clouds; but have you ever wondered why clouds float?  As long as the cloud is warmer than the outside air around it, it will float.

angels in the sky
cloud that looks like an angel

The height of the cloud in the atmosphere depends on the temperature and amount of water vapor of the rising air.  For example, drier air has to rise higher to cool enough to start condensation.

Microburst Monsoon cloud
vertically developed – cumulonimbus clouds

Cumulus clouds can grow into cumulonimbus clouds which are larger and often spread out in the shape of an anvil or plume. Cumulonimbus may produce heavy rain, lightning, severe and strong winds, hail, microbursts, and even tornadoes.

Clouds are grouped by their shape and by their height in the atmosphere.

Arizona storm clouds monsoon
Nimbostratus – rain bearing clouds

The characteristics of clouds are established by the elements available, including amount of water vapor, temperatures at the height, wind, mountains and other air masses.

The names of clouds come from Latin words that describe their characteristics. The main types of clouds are:

  • Cirrus means “curl” or “fringe”,
  • Nimbus means “rain-bearing”,
  • Stratus means “layer”,
  • Cumulus means “heap” or “pile”
arizona desert clouds
Cumulus cloud

Cumulus clouds are probably the most recognized clouds. These clouds form below 6,000 feet but in some extreme cases they can be in altitudes as high as 39,000 feet! They look like white, fluffy cotton balls. The reason cumulus appear fluffy is because bubbles of air, called thermals, linger in the cloud.

In mountainous areas, clouds may form lines at an angle to the wind. Wave clouds do not move downwind as clouds usually do, but remain fixed in position relative to the obstruction that forms them, for example: mountains.

clouds and wind
cumulus wave clouds by a mountain

Lenticular clouds form on the downwind side of mountains and are lens-shaped. Wind blows most types of clouds across the sky, but lenticular clouds seem to stay in one place.

clouds that look like UFOs
lenticular clouds are lens shaped

Strato-cumulus clouds form in altitudes below 6,000 feet.  Below photo shows a low layer of strato-cumulus clouds spreading the remains of larger cumulus clouds.

cumulus and stratus clouds
Stratocumulus clouds

Alto-cumulus clouds differ from Strato-cumulus  because they are slightly smaller. One easy way to determine if the cloud is alto-cumulus or strato-cumulus is to hold your hand up to the sky,  alto-cumulus clouds are about the size of a human thumb nail while strato-cumulus clouds are the size of a fist.

cumulus clouds
Strato-cumulus and Alto-cumulus clouds

Stratus clouds belong to the low cloud (surface-2000m, below 6,000 ft) group.  They are uniformed layered, gray in color and can cover most or all of the sky

stratus fog clouds
stratus clouds can look like fog

Stratus clouds can look like a fog  and are associated with overcast weather. Only drizzle comes from stratus clouds, if heavier rain falls then their title is changed to nimbostratus.

The most common of the high clouds is Cirrus.  These clouds are composed of ice and are thin, curly, wispy, feathery clouds. 

long cirrus clouds
wispy CIRRUS clouds

Cirrus clouds are usually white and predict fair weather even though they are so cold and composed entirely of ice.  They are the fastest moving cloud because the wind current is very strong at that high altitude.

identify clouds white long
Cirrus clouds

Cumulonimbus clouds belong to the thunderstorm clouds or clouds with vertical growth group. Reaching heights to 10km, high winds will flatten the top of a cumulonimbus cloud out into an anvil-like shape.

monsoon cloud in arizona
Thunderstorm clouds

Cumulonimbus clouds, also called Storm Clouds, cause heavy rain, lightning, hail, snow and tornadoes.

Cumulus clouds, which indicate low-level atmospheric moisture often precede storms. In this picture of a Cumulonimbus cloud or thunderstorm cloud, much lightning was occurring with the winds increasing rapidly.

Arizona monsoon weather storm clouds
Cumulonimbus cloud – Thunderstorm clouds

Mammatus clouds are pouches of clouds that hang underneath the base of a cloud. They are usually seen with cumulonimbus clouds that produce very strong storms.

storm clouds cumulus
mammatus clouds

Mammatus clouds look like a field of tennis balls, melons, or like female breasts. That is where the name comes from.  

Cirrostratus clouds form in the 18,000 feet and above. The refraction of light by the ice crystals in the Cirrostratus clouds cause a halo around the sun or moon.

stratus clouds
Cirrostratus clouds

You can not see the halo when this happens but the sun or moon will be less visible because the Cirrostratus clouds condense too much for clear visibility. Clouds are usually white and predict fair weather. These clouds often follow Cirrus clouds therefore Cirrostratus clouds are indicators of good weather.

Desert Monsoon weather, facts and details

What is MONSOON?  The word monsoon is derived from the Arabic word mausim, which means season. Traders fishing the waters off the Arabian and Indian coasts noted that dry northeast winds in the winter suddenly turn southwest during the summer, and bring heavy rains to Asia.

mexico arizona storm weather
summer Monsoon flow graph

We now know that these Monsoon large wind shifts from dry desert areas to moist tropical areas occur in other parts of the world including Arizona.  Strong yearly variations of temperature over land masses is a primary cause of MONSOON.

Tucson Phoenix Monsoon Season map
Monsoon Information weather chart

The monsoon weather in Arizona is not as intense as Monsoon season in Asia and India mainly because the Mexican Pleateau is not as high or as large as the Tibetan Plateau in Asia.  In Arizona, the monsoon process starts with the hot and dry weather of May and June.

Tucson, Phoenix, AZ Monsoon weather storm clouds
Monsoon dark clouds over Coronado Mountains

Most of Arizona’s humid air comes from the Sea of Cortez and the Gulf of Mexico. Our hot desert sun heats the moist air causing the familiar thunderstorm cumulonimbus clouds.

Monsoon weather Arizona storm clouds
Cumulus clouds, Monsoon thunderstorm

Cumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means “heap” or “pile” in Latin. These clouds typically form when warm air rises and reaches a level of cool air, where the moisture in the air condenses.

If the top of the cumulus cloud reaches above the altitude where the temperature is at or below the freezing level, then precipitation from the cloud is possible. 

Usually by May or June,  our strong Arizona heat causes temperatures to soar over these desert land areas. The intense heat causes surface air pressure to fall, forming an area of low pressure known as a thermal low.

Eventually, the cooler and much more humid air over the ocean is drawn toward the hot, dry air over land. This moist air moving onto the hot land eventually becomes unstable and develops into thunderstorms.

Once this occurs and rain begins to fall, humidity levels increase over land, which only triggers more thunderstorms.  Now you have the Arizona Monsoon Season!

This cycle will continue until land areas begin to cool in the early fall and the monsoon gradually ends.

Dark Monsoon Storm Clouds Arizona
Thunderstorm cumulonimbus clouds

Until the late 1970s, there was serious debate about whether a monsoon truly existed in North America. However, considerable research, which culminated in the Southwest Arizona Monsoon Project (SWAMP) in 1990 and 1993, established the fact that a bonafide monsoon, characterized by large-scale wind and rainfall shifts in the summer, develops over much of Mexico and the intermountain region of the U.S.

Dark Thunderstorm Clouds Monsoon
Monsoon Clouds , Microburst cloud in desert

Rainfall during the monsoon varies with distinct “burst” periods of heavy rain and “break” periods with little or no rain. Monsoon precipitation accounts for a substantial portion of annual precipitation in northwest Mexico and the Southwest U.S.