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Height of base:

Between 600 and 6000 m (2000 - 18000 ft) (low to mid-level clouds)


Very dark, grey ragged shreds; featureless layers

Steady precipitation (rain, snow, graupel)

Ragged base

No visibility of sun

Deep layers, extending over large areas


World-wide; common in midlatitudes

Made of:

Supercooled water droplets, snow crystals, ice crystals, rain drops


Moderate, steady precipitation


Lowering of altostratus

Droplet growth through coalescence

Ice crystal growth through Bergeron-Wegener process

How to distinguish from

Altostratus (As)

Ns is darker and produces heavier precipitation

As often allows to determine position of sun

Cumulonimbus (Cb)

Cb produces intermittent very heavy precipitation

Thunder, lightning and hail are signs of Cb


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Nimbostratus with pannus

(Hebgen Lake, June 2006)


Freiberg, Germany, July07


Fichtelberg, Germany, July07


Lansing, Michigan, Dec07





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Last modified: 1/14/2008

Maintained by Sylke Boyd


The views and opinions expressed in this page are strictly those of the page author. The contents of this page have not been reviewed or approved by the University of Minnesota.