If you have followed my work for some time, then you recognize that I am often mentioning relative performance comparisons between indices. For example, I mentioned on Sept 20th concern that both Small Caps- RUT and Financials - RIFIN were weakening relative to SPX. While SPX was flirting with the highs from Friday Sept 16th, the picture was much different for these indices.
Many times it is the subtle things to pay attention to, and this weakening was indicating at least some type of pullback was approaching. The strength of the selloff was surprising, and was not picked up by my cycle analysis method which was unusual.