Nimbostratus

Latin Translation 

Nimbus = “rain bearing” 

Stratus = “flattened” or “spread out” 

Height  

Between 6,500 to 23,000ft (~ 2000 to 7000 metres) in mid-latitudes. 

Nimbostratus clouds tend to be thick, between 2km and 8km. This can block a lot of sunlight, making the day feel dull even if it isn’t raining.

About 

Nimbostratus clouds are thick mid-level clouds. They turn the sky dark grey and are associated with persistent rain or snow.  

How do they form? 

They often form when a relatively warm, moist airmass meets a colder airmass (such as a warm or occluded frontal boundary). The colder airmass cools the water vapour along the boundary, forming water droplets or ice crystals (cloud). Once the cloud is thick enough, the water droplets or ice crystals become too heavy to stay aloft and fall as rain or snow. The cloud that they fall from is nimbostratus.  

How to spot it? 

Nimbostratus is quite a featureless cloud, and often hard to see in heavy precipitation. But if the sky is dark grey with persistent rain or snow, then it’s likely to be nimbostratus.