This year's flattish stock market hides a sea of turbulence under the surface—and that could be the early warning signs of a long-overdue stock market correction, some strategists say.
The S&P 500 is up about 1 percent for the year, but as of early Wednesday 56 percent of the S&P stocks were down 10 percent or more from their most recent highs. Some names in the energy sector, like Marathon Oil, Noble Energy, Transocean and Apache were down more than 50 percent.
"I think this is it. At least, it's a seasonal bull market correction. Kind of all signs point to that," said Ari Wald, technical analyst at Oppenheimer Asset Management. "You have the internal breadth breakdown. More stocks are really starting to diverge with the broad market. Momentum is waning and seasonals are very weak."