Courtney's Cloud Corner: Cumulonimbus Clouds

You know the drill- it’s humid outside, you look towards the sky and find some angry clouds approaching looking dark and elongated. There is bound to be some rain and possibly some severe weather. We all know what Mother Nature has in store for the near future. Some may flee at the sight and some bask in the drum these clouds will make. Although, what are these large and dark appearing clouds? Cumulonimbus Clouds.

These storm clouds come from the Latin words cumulus “heaped” or “pile” and nimbus “rain”.  They can rise up to about 12,000 meters or 39,000 feet, and form in unstable atmosphere. They are created in three stages: the Cumulus stage, the Mature stage, and the Dissipating stage.  During the Cumulus stage the Cumulus stage, warm moist air (or thermals) rises through an updraft. These thermals will continue to rise, cool, and condense. All the clouds need is to continue growing in some forcing triggers. These triggers can come from ascending up a steep incline, a frontal boundary, convergence, turbulence or simply warming the earth’s surface.  If the updraft continues ascending warm moist air in an updraft, the cloud will continue to grow. This leads to the Mature stage.

In the Mature stage, the raindrops begin to grow and the cloud begins to expand to great heights. This stage is when the Cumulonimbus cloud has been built. The droplets within the cloud collide with other drops and begin to become heavy. Once they become heavy enough, they descend through the Cumulonimbus cloud. Both the droplets and cool air rushes to the surface, called a downdraft.  During the Mature stage, both updrafts and downdrafts can occur. If the updraft continues so does the storm. If the updraft weakens and the downdraft take over, our final stage will appear, the Dissipating stage.

The Dissipating stage is the ending stage of the Cumulonimbus cloud. Eventually the downdraft overpowers the updraft by limiting its supply of warm moist air. It leaves behind the reminisce of what was a Cumulonimbus clouds.