photo #6799723

Doug Goold (Member 56,370) spotted an Altocumulus volutus, or roll cloud, off the coast of Newcastle, New South Wales, Australia. This long, smooth tube of cloud likely formed due to cool sea breezes flowing in from the ocean interacting with warmer air over the land. Roll clouds are rare formations, but one place to look for them is over coastal waters like this. Normally, they appear lower in the sky (when a roll cloud would be described as Stratocumulus volutus), and it is particularly rare to see a mid-level version like Doug’s Altocumulus volutus. Since it is a formation that can be caused by the coastline, a roll cloud can extend over a long distance. ‘It was sitting just above the coastline,’ Doug remembers, ‘and extended north-east to south-west for about 100 km [60 miles].’