Picture courtesy of Freedigitalphotos.net by Jennifer Renee
Nimbus is one of the 5 main cloud categories and simply means rain bearing (from the Latin). The others are: Alto – high, Cirrus – thin and wispy (see my previous post on Clouds for an example), Cumulus – puffy and Stratus – layer (Latin for spread out).
The latter four categories are cloud names in their own right. Nimbus is always combined with another to give a cloud name. All the categories may be combined with others to give us a wide variety of names, which if you know the above code it tells you exactly what the cloud is like: thus Altocumulus means a high, puffy cloud. The most dramatic is Cumulonimbus which is the very tall, puffy rain bearing cloud often with an anvil shape at the top. It's this type of cloud which gives us the stormiest of weather.
There are many sub-categories of cloud and the list is still being added to. For example there's Mammatus, which is a special bubble shaped form of Cumulonimbus. I saw an example of these last year on my way to Malvern Spring Show. Have a look here for a full list of clouds with links to their definitions.
For more in the way of N, do visit the ABC Wednesday blog.