A SPECTACULAR cloud formation over St Albans on Tuesday evening caught the eye of local resident Ian Pattison who took this photograph from Holywell Hill. It followed a brief downpour of rain at around 7.30pm during a day which was showery and overcast. T

A SPECTACULAR cloud formation over St Albans on Tuesday evening caught the eye of local resident Ian Pattison who took this photograph from Holywell Hill.

It followed a brief downpour of rain at around 7.30pm during a day which was showery and overcast.

The Herts Advertiser forwarded the picture to the Met Office for a view on what weather conditions could create such a sight and why.

The explanation was that it was a good example of a cloud formation called mammatus which was usually associated with severe weather conditions.

A spokesperson for the Met Office explained that as the photograph shows, it is a spectacular and distinctive cloud formulation that consists of pendulous globules of cloud - mamma is the Latin for breast - that hang from the underside of stratocumulus or cumulonimbus clouds, especially underneath the anvil of the latter.

They are caused by powerful downdrafts when pockets of cold, moist air sink rapidly from the upper to the lower parts of the cloud, reversing the usual cloud-forming pattern of the upward convection of warm, humid air.