On Saturday, 16 August 2014 18:39:47 UTC+1, wrote:
Looking at the visible satellite image there seems to be widespread wave-like structure in the clouds over most of the UK and Ireland. I know about gravity waves which form in the lee of mountains etc., so is it simply topography which is causing all the structure apparent today? The wavelength is greater in southern Scotland than elsewhere. Is this due to the greater range of topography?

It's topography that initiates it but to generate a long stream of waves you need a certain temperature structure which normally involves an inversion. There is a strong one at about 850 mb (about 5000 ft). The air cannot readily rise through this and is forced to bounce back, keeping the wave going. A bit rough and ready, admittedly, but it may help. :-)

Tudor Hughes, Warlingham, Surrey