What were these rare clouds spotted over Vancouver? [Video]

Weather watchers were treated to a unique display on Friday evening as rare cloud formations filled Vancouver skies.

The weather phenomenon cast sheets of grey-tinged cloud, knitted together to form an undulating pattern, across skies from North Vancouver to Port Moody throughout the evening.

The striking weather was a result of asperitas clouds, an exceptionally rare cloud formation that holds much mystery even for forecasters, said Environment and Climate Change Canada meteorologist Nan Lu.

“Unfortunately, we currently do not have a clear answer for their formation,” said Lu.

Typically, they tend to appear before and after storms, and while little is known about why they occur the formations are believed to be associated with unstable atmospheres, she said.

Changing wind directions are likely the reason behind the wavy texture of the clouds, she added.

According to the Met Office, the first documentation of the cloud formation to the World Meteorological …