Well, try not to concentrate too much on the broadband patterns.
What you're seeing is the contact's bearing and its bearing rate over time.
Low bearing rate (traces that are mostly vertical) usually mean that the contact is distant and/or mostly on the same course as you are. A trace that shows a lot of a curve towards the horizontal means the contact's bearing rate is changing.
This could be due to speed, closer range, CPA, or a maneuver (aka, a Zig). When you see that big bend in your waterfall display, its usually a good time to check your solution to see if its holding up.