The lines run perpendicular to the direction the swell is moving, just like swell lines in the ocean. The colors vary depending on direction.
This is a hobby project by artist and game developer Dave Frampton - @majicDave. I've written an application which takes freely available GFS and WAVEWATCH III weather model data, and produces nice looking images. I will try to keep these images up to date, but make no guarantees on the reliability or accuracy.
Times and dates are displayed for your local timezone.