The white line in this Directional Movement Indicator is an average (ADX) of the DX. It is high when it is over 40. On my chart there is also a DX line, which combines positive and negative direction to show a total. When this line gets over 60 it indicates real overbought or oversold conditions and means there will be near term selling or buying. This has happened three times this year, as indicated by the dotted vertical lines.
I bought 7/24 expiry 370 puts, and 7/17 expiry 385 strike puts (which I will sell Wed-Thurs), small position of each.