Weather HD animation

I just want to know how is the animation done in the Weather HD App: http://itunes.开发者_如何学运维apple.com/us/app/weather-hd/id364193735?mt=8

Is it done by Images, Videos, actually animation or a mixture of all.

To me it looks like that (mix) and how to actually implement it. I just want to get an idea of how to do something similar.

Thanks

It looks like this is all done by videos. There are 30 videos with a total size of about 100 MB in the app bundle (free version). There are separate videos for iPhone and iPad.