Something I often do when I see the 'hair squigglies' on the forehead is to select the hair in question, and scale it to 101% or so, at the 'root' of the hair node tree (i.e. not head, hip, etc). This is the 'universal' scale slider, not the x, y, or z sliders individually, although sometimes I might mess with those as needed. This usually works. Sometimes I'll try adjusting parameters individually, but I usually do that when I first add the hair, to get the hairline, etc. where I want it. Afterwords, I mostly use the hair parameter morphs for moving ponytails, bangs, etc. around.
For me, the squigglies usually appear after I apply a pose, which seems to be the case in the example above.
But yeah, the 'scale up 1% or so' trick usually works for me.