What You Need to Know:
Name(s): Altocumulus Stratiformis; Ac Str
Common Altitudes of Formation: 2,000-6,100m (6,500-20,000ft)
Signals: The altocumulus stratiformis clouds are a harbinger of possible bad weather and unstable conditions. It will signal an exchange of the current fair skies with periods of unsettled weather.
Meaning of the Name: alto- high, cumulus-heap; stratiformis- spread out in an extensive horizontal sheet or layer
Elaborated, more comprehensive information:
This species is the thinnest of the altocumulus genera. Their formation is the result of light low-level winds carrying water particles to medium altitudes. Wind shear at this altitude forms the water particles into altocumulus clouds.
Altocumulus clouds are usually found between the warm and cold fronts in a depression. The stratiformis is identifiable by the individual cloudlets and its occupancy of a large amount of sky.
Cloud 9 