Working on some slides for a seminar last week, it was apparent that breadth indicators on the NASDAQ signaled a divergence from the price action of the market.
Looking specifically at AD Ind and HI/LO, although other breadth measures told the same tale.

The AD indicator explained


The Advance/Decline Indicator is an exponentially weighted average of the net advancing versus declining issues. With this indicator, the direction of the trend is of importance and not the actual value of the indicator. When the indicator is increasing, advances are outweighing declines, and when it is decreasing, there are more declining is­sues than advancing.
The  Advance/Decline Indicator is a breadth indicator very similar to the Advance/Decline Line.  However, this indicator tends to be more sensitive and at times will signal a move earlier than the Advance/Decline Line.
The breadth was telling us something was amiss from last week. Take a look at this chart of the NASDAQ clearly a divergence was in place before the downturn.
Today’s (10-10-18) 316 point drop in the NASDAQ a 4% drop and nearly 9% drop from the high is close to the 10% corrective point and some buyers may come in over the next few days and keep the decline in check or not.
The markets are down between 6 and 10% in 5 days. Keeping good stops is a must in your portfolio to protect you from the worst of this. Using trailing stops between 7 and 10 % on stocks that are moving and protective stops 5 to 7 % below initial investment for example can easily reduce your losses in these volatile markets.