Above: Nimbostratus


Nimbostratus clouds are a cloud formation that is characterized by their shapeless appearance. The Latin word "Nimbus" denotes precipitation and therefore the cloud title Nimbo reflects this. As a stratus cloud it is identified as being a low level cloud. This is actually a fascinating point, as this cloud normally is formed in the medium altitude levels that are between 6,000 and 20,000 feet, but on formation nimbostratus clouds descend to lower levels as they begin to produce rain.

What are nimbostratus clouds?

Nimbostratus clouds are easily identified as a shapeless grey cloud that appears uniform in color and when formed will bring rain. Nimbostratus clouds start life as another form of cloud that develops into nimbostratus clouds. They are normally very thick compared with other clouds types and can be as much as 2,000 feet in depth, this helps to explain their often dark grey color.

Types of nimbostratus clouds

  • Nimbostratus virga
  • Nimbostratus pannus
  • Nimbostratus praecipitatio

What height are nimbostratus clouds found?

Nimbostratus clouds start their formation at medium cloud levels as altostratus clouds. They will begin to cause rain to fall from altitudes as high as 10,000 ft. As they develop and continue to rain, the clouds gradually begin to descend and once there cloud base drops below 6,000 feet therefore they become  defined as low level clouds and so are classed as nimbostratus clouds.

Classification of nimbostratus clouds

As a stratiform cloud nimbostratus clouds are in the D1 class of clouds, they get this classification as they are rain bearing. This classification applies in parts to all rain bearing clouds regardless of their altitude. 

How are nimbostratus clouds formed?

Nimbostratus clouds are formed at medium altitudes and then they gradually descend to lower altitudes where they are able to cause rainfall to start. As they descend they grow in their density and this allows the rain to start falling in a light drizzle that can develop into a more steady rainfall that can continue for some time. Having been formed they can last for days or even a week or more if the weather conditions do not change. As they are more frequently found in the middle latitudes of the earth, neither the poles nor the equatorial zones, they are able to remain in place for a longer period of time without being disturbed by strong weather fronts driving in.

What do nimbostratus clouds look like?

They are very featureless clouds that appear as a dark grey cloud carpet that progressively covers the sky as the nimbostratus cloud gains more moisture and therefore is ready to start raining. Essentially the nimbostratus cloud is one of the most formless and featureless types of cloud that can be observed in the sky.

How common are nimbostratus clouds?

You will be able to find nimbostratus clouds in the following conditions:

  • In temperate regions rather than at the poles or the equator


  • They can best be found during the autumn and winter when weather conditions are generally quieter and there is little variation in temperature

Where can I see nimbostratus clouds?

In most parts of the world nimbostratus clouds can be observed. The best place to see them is in continental areas well away from the oceans and the associated stronger winds.

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