Self-explanatory short. This center-line has served fairly well. Note how price usually never stays exactly on the line but fluctuates back-and-forth on either side. Center-lines can be thought of as picket fences in that sense.
In light of the current considerable downward momentum, I suspect price will simply come up for a final touch of this line, but fail to get onto the other side of the "fence". If it does, stops do not need to be far above 550.