A blanket of unusual clouds formed over Sydney on Tuesday in the latest of a string of bizarre weather events in the last few weeks.
Awestruck observers along the New South Wales coast shared photos of the ominous sight, revealing oddly clumped dark clouds rippling across the sky.
Though uncommon, experts say the phenomenon is no cause for worry; the distinctive ‘lumpy’ clouds are known as mammatus clouds, and form in association with storm-causing cumulonimbus clouds.
Pictures of the unusual formations have been popping up all over social media since yesterday.
The clouds appear as a thick blanket covering the sky, concentrating in lumpy masses toward the center with a smooth, flat outer edge.
These are mammatus – or ‘mammary’ – clouds, coming from the Latin term for breast or udder.
Typically, turbulence within the cumulonimbus cloud will cause mammatus to form, especially on the underside of the projecting anvil as it rapidly descends to lower levels.
This reverses the usual cloud-forming process of upward growth, making for an uneven cloud base.
Meteorologists say it could signal coming arrival of thunderstorms, which are forecast to begin moving through the region and could bring hail, heavy rains, and high winds.
Over the last few weeks, Sydney has been experiencing a lot of strange weather, from unexpected fog to hail stones that look like flowers.
In mid-December, an ominous mid-morning fog rolled through Bondi Beach and cast an eerie haze over the region as a result of moist conditions over the sea.
Just days later, on the 21st, social media lit up with photos of strange ravioli-shaped hailstones that many likened to flowers or tiny planets.
On the same day, stormwatchers posted eerie photos of green lights spotted in the clouds amid the hailstorm.
While it isn’t clear what exactly causes the phenomenon, experts suspect it has something to do with the filtering effect of thunderstorms.