Hello everyone,
the first thing I should say is that I know very little -- close to
nothing -- about meteorology. I find it very interesting, but I just
never got into it.

A few months ago, while browsing wikipedia, I came across a curious
meteorological phenomenon which took place in Australia (or New Zealand,
I can't remember).
It is a 'wall of clouds' which forms suddenty and discharges a violent
storm. I remember reading some pages on other websites about it, and how
some crazy people 'rode the clouds'.
If I recall correctly, it's a common event in a specific part of
Australia (or NZ, again), but for some reason it's not widely known by
the rest of the world.

Could anyone give me some hint about its name? I vaguely remember that
it has "Great" in its name, but I'm not 100% sure.

Thank you very much!
--
Jollino