I made this video clip starting with a directory of individual radar images in PNG format and then used the mencoder tool (part of mplayer) to generate a MP4 video clip from the frames.
mencoder mf://*.png -mf fps=5:type=png -ovc lavc -lavcopts vcodec=mpeg4 -o video.mp4
Note that I've set the frames per second to 5 (fps=5). The usual 24 frames per second is too fast.
Images from Met Éireann (the Irish Meteorology service).