| Altocumulus stratiformis | |
| Image Location: | Altocumulus stratiformis translucidus.jpg |
| Image Name: | Altocumulus stratiformis over Germany in 2011 |
| Abbreviation: | Ac str |
| Genus: | Altocumulus (high, heaped) |
| Species: | stratiformis |
| Variety: |
|
| Altitude M: | 2,000 - 6,000 |
| Altitude Ft: | 6,500 - 20,000 |
| Level: | medium |
| Appearance: | Patchy and shallow; often semi-transparent. |
| Precipitation: | Uncommon |
| Thickness: | < 500 m |
Altocumulus stratiformis is the most common species of the Altocumulus genus of clouds.[1] They tend to form broad layers of individual, cell-like clumps, often separated from each other, though they sometimes can coagulate into a larger individual cloud. They often have a vertical extent of less than 500 m.[2] Due to their formation dynamics, they are commonly associated with the imminent arrival of precipitation.
The presence of stratiformis clouds in the mid-levels of the atmosphere is indicative of some instability at that level;[3] atmospheric pressure falls, often associated with nearby systems of low pressure, can depress the altitude of stratiformis into the lower atmosphere, often evolving into Nimbostratus clouds, which precipitate. [4] Altocumulus stratiformis clouds may also form when a cold front is approaching, due to the difference in air masses.