Why markets may be setting up for a Yellen surprise

Markets are only half listening to the Fed, and that leaves room for a bigger reaction if Fed Chair Janet Yellen sounds as hawkish as the comments of some other Fed officials suggest she might.

"The market has shut them out. The market is only pricing a 50/50 chance of a hike this year. If they want to get this done, and they don't want to shock the market and create a whole repeat of last year's market volatility from not going [last September] … they have to inject the expectations of another rate hike. The best defense is a good offense," said Robert Tipp, head of global bonds and foreign exchange at Prudential Fixed Income.

Over the weekend, Fed Vice Chair Stanley Fischer joined two other recent hawkish-sounding Fed speakers, who were pushing the idea in speeches last week that the Fed is close to raising rates. Fischer's message was more on the economy, and he said the Fed is close to meeting its objectives, a comment taken as slightly hawkish.

"I think the confluence out there suggests that there must be a consensus across the Fed that they will get a rate hike done this year, if they can," said Tipp. "I think she will aim for the dovish hike. The problem with the dovish hike is I don't think you can do that in September. If you want to do so, a dovish hike is much easier in December. If you do it in September, you're going to have a lot of participants pricing in another hike in December." Tipp said the Fed wants the door to be open for a September hike, though it's highly unlikely it would act then.

"It's just not going to happen in September, in my opinion," said McCarthy. "If anything else, the Fed does not want to throw itself in the crosshairs of this potentially ugly presidential campaign one week before the first debate."