Strange clouds and storms swirl over Sydney

Spectacular mammatus or 'mammary clouds' form over Sydney as storms swirl nearby

ABC

3 January 2019

As hail, heavy rain and storms continue to hit multiple areas across New South Wales, keen weather-watchers have documented unusual cloud formations called mammatus, or "mammary clouds", in the skies over parts of Sydney.

A number of people have posted snapshots to our ABC Weather Obsessed Facebook groupdocumenting the clouds.

Mammatus clouds appear as rounded pouches or bulges hanging underneath the base of a cloud, and are generally associated with severe weather or storm activity.

The word "mammatus" is a Latin term that means breast, udder or mammary gland, and the clouds form their distinctive shape when cold air sinks below the cloud.

Mammatus clouds appear as rounded pouches or bulges hanging underneath the base of a cloud, and are generally associated with severe weather or storm activity.

The word "mammatus" is a Latin term that means breast, udder or mammary gland, and the clouds form their distinctive shape when cold air sinks below the cloud.

PHOTO: Mammatus clouds photographed over Manly Dam on Sydney's northern beaches. (Supplied: Laurie Wilson, Facebook)

According to the Bureau of Meteorology (BOM) Storm Spotters Handbook, the clouds are "dramatic, beautiful adornments, especially when side-lit".

PHOTO: Mammary-shaped clouds seen over Sydney's Olympic Park. (Supplied: CJ Lightning, Facebook)

Mammatus clouds are often associated with extreme weather, but when they are formed in the sky it merely indicates "descending pockets of small droplets or ice crystals from an anvil surface", BOM said.

PHOTO: Unusual mammatus clouds over North Curl Curl beach on Sydney's northern beaches. (Supplied: Lorraine McManus, Facebook)

And, according to BOM, while they might look pretty dramatic and often appear around the same time as severe storms, mammatus clouds themselves are perfectly harmless.

PHOTO: Mammatus clouds in the sky above a suburban Sydney street. (Supplied: Debbie Barnes Reid, Facebook)