Roger's SkyPix

Mini Cloud Atlas

Altostratus Undulatus Asperatus

Altostratus Undulatus Asperatus

These sharply defined undulations to altostratus formations have taken on a new name in the cloud-watching community, asperatus, derived from a Latin verb meaning "to make rough". They occur most often in areas of elevated low-level warm advection, atop a relatively stable boundary layer. Such conditions often exist either in the morning or behind an earlier area of storms and precipitation. Asperatus formations seem to be relatively common on the American Plains, probably because of fewer intervening low clouds to block the view. Back in 2000, before hearing of the term asperatus, I photographed a skeletal example, surrounded by blue sky and topped by small convective turrets, from the roof of NSSL in Norman. This was a larger field of such clouds but not quite as deep in wave amplitude.

2 NNE Hoople ND (10 Jun 12) Looking SW