The clouds shown in the photo has the name Kelvin Helmholtzbølger. These waves occur when you have two air masses of different density and a wind shear between them.
When one has lighter air on top of a little heavier air, and there is a difference in wind speed, and / or direction of the two air layers, one can get these waves.
Where these two air masses meet arise anything like a call interface. Limit Plata contain small disturbances, which gets air to rise and fall. It is this movement one can see in the image.
Look for the atmosphere is always trying to come back to its normal state, these clouds have relatively short life.
Mountain Waves
Some other clouds that are formed in a similar way, the lens clouds or almond clouds. These are formed on the leeward side of the mountain or hill drag when it blows strongly across the mountains. Airflow is set when the wave motion.
The air is pushed upward in waves, which are cool, and it is formed cloud droplets. These clouds are a sign of mountain waves
Read more: Found strange cloud in the Kilimanjaro
Greetings from Haldis Berge