with the arrows pointing in the direction of "lift"
In essence. Strictly, the graphic shows a representation of pressure variation via pressure tapping measurements.
I've just done a few net searches to find some interesting stuff to illustrate what is going on.
this is a basic setup video for the pressure tappings
this gives a more serious story. Unfortunately the pressure variations are shown as a graph rather than as direct pressure tapping pressures which are the basis for the picture in megan's post.
I found this video showing the manometer height variation with alpha. Not as useful as I had hoped to find but it gives you the idea.