In actuality, all the indexes can be seen to have this expanding shape in the all-hours mode which may be the clue that this is a Minute [iv] and these spasms higher are the final burst of P2.
Just my theory. See my RUT chart for one index in which this translated pretty well http://1.bp.blogspot.com/_TwUS3GyHKsQ/S0KkJieKEkI/AAAAAAAADWM/Yp_uk8caYwE/s1600-h/rut30.png
The best-hidden triangles are the ones that work best and I kick my self for not spotting them over the past weekend. Who can deny that the move up from Monday wasn't a thrust -type move?