[Pleasures]

Dark, brooding and menacing. This apparition, which materialised over the skies of Hertfordshire, looks like an expensive special effect from a horror movie.

The strange globular clouds, which resemble drops of oil poured into a murky pond, appear to herald the appearance of an alien spacecraft, here to cause havoc.

In fact, this picture shows a rare but perfectly natural (and perfectly harmless, provided you do not try to fly through it in light aircraft) meteorological phenomenon known as a mammatus cloud.

Freak: The weird weather is called a mammatus from the Latin word for breast

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Spoiler!

Named after the Latin for breast, mammatus clouds are associated with the powerful storms which can occur in the summer, and are a sign of the massive quantities of water vapour that are held in the languid summer air.

Mammatus lobes can form under several types of cloud but this particular spectacle appears to be associated with the cumulonimbus thunderclouds which caused the storms that afflicted much of southern England last week.

How they form is something of a mystery.

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Foreboding: Ian Pattison photographed the outside his home in St Albans, Herts

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Clouds in general consist of water droplets, ice crystals or a mixture of both, and the shapes of the various cloud forms are caused by a number of factors such as temperature, the ratio of water and ice, the altitude of the cloud and the windspeeds within it.

The exact forms are also governed by a complex interplay of wind, rising and falling air, and changes in humidity and density.

But while most clouds have wispy edges, mammatus lobes, which are usually stable for only a few minutes-have unusually sharp and well-defined boundaries. Each lobe can be up to a mile in diameter.

They are also nearly opaque, making them look far more tangible than a mass of droplets and ice flecks.

This picture was taken by Ian Pattison, 31, an assistant librarian, outside his home in St Albans last week. He said: 'I got a new phone last week and when I saw this amazing sky, I just grabbed it and started snapping.'

Strange clouds such as these are probably behind one of the most perplexing phenomena of modern times - the UFO sighting.

When agglomerations of condensed water vapour become concentrated-enough, and the light strikes them in the right way, some low-level clouds can give the appearance of being solid objects.

But there was nothing alien over the skies of St Albans last week. Just a lot of very British rain and a sheet of spectacular, if rather unsettling, water droplets in the sky.

Spoiler!

Do you know your cirrus from your cumulonimbus?

1. Is it Altocumulus, Altostratus or Cumulonimbus?

2. Is it Stratus, Stratocumulus or Nimbostratus?

3. Is it Cirrostratus, Cirrocumulus or Cirrus?

[xibo]

please reformat your post.

[Pleasures]

lol i tried to tidy it..but the images messed it up..how do i get the words under the picture? i entered Enter but doesnt go down.

[KLoWn]

Shit i would've want to see that, i love clouds and stuff like that.

[flyingwind]

....Nice cloud formations.....

[rakaz]

its nice to watch cloud in sunny days.

[Beba]

this is really nice,,
sorta sad, but that's the beauty of nature..
thanx for the post, and sorry i can't help u with ur problem..

[InDiGo]

Hmm... they sure know how to name such things.

[Renji]

Very interesting cloud formation, and a well-taken photograph. You can really get the details of the clouds' shape.

[xo chriis]

I've always wanted witness clouds like that in person but unfortunately nothing like that seems to happen where I live. Clouds are very beautiful.