We have recently added a new feature to the animation menus of the GFS and NAM models. At the bottom of the animation menu bar there is a place to select NAM/GFS Comparison and dProg/Dt. The model comparison allows you to have a side by side animation of the NAM and the GFS model for the same time periods.
The dProg/Dt feature which is available on the NAM currently, allows you to compare the current model run to the previous model run, a 6 hour difference.
We will be adding many more features in the coming months that will give the user more flexibility in the type of animations.
Please feel free to provide us with feedback on what you would like to see.