[JOKE_SNOW]

Pictures simply can't do the justice of representating just how large and under-hanging these mammatus formations were which followed a particular strong cell at the end of this convergence-zone day. The cell in question looked relatively benign as it was crossing into the western peaks however thanks in-part to max daytime heating and the convergence, the cell literally exploded into life within tens of minutes.
Thunder once every 30 seconds and torrential rain blanketing the moorsides, it wasn't until the back-edge started to move through before I realised the spectacle to follow.







The mammatus were under-hanging from mid-altitude, so much so that downdraughts were forcing them to the surface in places as areas of precipitation. It was a textbook example of when a TCU rapidly develops into a CB, but then exhausts its energy through latent heat and evaporative cooling takes care of the rest.
Photography wise the ISO settings were all over the place so I went with 64-100 to compensate for the back lighting of the sun, which turned out a little grainy but luckily boosted up by HDR and a bit of tweaking with contrast settings.

[Bazmundo]

Impressive, could you possibly resize them? If not, I'll have a crack at getting them down to 800px.

Done.

[Conrad]

I have never seen mammatus that big before. Nor had I ever heard of the mamma reaching ground level but clearly it is possible. There was something special about this storm. Maybe a lot of very cold and dry air higher up?

[skanky]

I think that's part of the same system that moved through here. The mammatus then was stll big. The second last in my set gives some idea as it waned, but the image doesn't show it as clearly as it was to the naked eye.

Great shots.

[Chris CW (aka Seedubs)]

Oh cracking Mamma, huge too! Thanks for posting, are these the same that were on NetWeather?

Can someone with more knowledge explain how they form and why?

[JOKE_SNOW]

I'm not sure if PICASA can resize images but i'll have a shot. Recently moved onto that platform for its ease of HDR manipulation but have still yet to master it. Yep I Posted 2 of these shots on 'the other' website aswell lol, and these are no doubt the same mammatus you guys in Sheffield also saw. Although I didn't photograph it, behind this lot towards Bleaklow there was even more beginning to form but low-level cloud didn't allow the mammatus to become bathed in sunlight and so the features were less evident.

You're more than welcome to have a go at resizing Glyn. In hindsight given the ISO noise, at least I know next time to boost it up to 200 at the least for exposure compensation.

[Floss the dog]

Wonderful photos. Thanks a lot

[mrfizz]

Faaaaaaaantastic!

[Bazmundo]

JOKE_SNOW, on 13 April 2012 - 11:24, said:

I'm not sure if PICASA can resize images but i'll have a shot. Recently moved onto that platform for its ease of HDR manipulation but have still yet to master it.

Picasa can resize using the 'Export' function, though it's "HDR-ish" is an effect and not true HDR image-stacking.

I did it quite simply using MS Office Picture Manager, though that does lose a little quality on resize...

[Lin]

Wow! That is seriously impressive mama!

[Chris CW (aka Seedubs)]

For resizing etc, just download Infraview (http://www.irfanview.com/), its free and handy.

[Ed.]

Can only echo all comments so far - that sure is one heck of a show! we got a fair bit our way but nothing quite so special

[OCEANSTORM]

Wow! Those are really impressive, I've never seen anything even near to such a scale as that!