This will be key factor in future Fed decisions

Don't expect the Fed to have any big surprises in 2016, no matter what current conditions might suggest.

As a history-making year comes to a close for the U.S. central bank, investors continue to try to read the tea leaves as to what to expect in the 12 months ahead.

A divergence in expectations between where the market expects rates to be and where Fed officials have placed their own estimates has convinced some that the Fed may take on a more hawkish tone.

On one hand, there was the so-called dot plot, or the diagram where Federal Open Market Committee members indicate where they think the fed funds rate will be in the years ahead. According to the chart released along with the rate hike, the FOMC expects four moves in 2016 — presumably one at each of the meetings where Chair Janet Yellen holds a news conference afterward.

On the other hand, there are market participants — namely the traders who place their own bets on when the Fed will move on the rate banks charge each other to borrow money. Futures are indicating the likelihood of just two or three increases in the year ahead, with a 60 percent chance the first will come in March.

This conflict, the thinking goes, could rattle markets that have come to depend on the Fed for a historically high level of accommodative monetary policy.

Read MoreThe Fed raised rates. So what happens now?

In some quarters, the allegedly hawkish tone of the central bank statement was even welcome news to those who think the FOMC should be more aggressive now that the Dec. 16 rate hike is behind it.

Janet Yellen
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Janet Yellen

"If the backdrop unfolds as we expect (we will stress again for emphasis: the hurdles are lower than most people seem to appreciate) not only will the market be wrong to think that the Fed will hike only twice next year, but the Fed's forecast of four hikes could actually prove too conservative," Tom Porcelli, chief U.S. economist at RBC Capital Markets, said in a note to clients.

The problem with that view is that the Fed — the Yellen Fed in particular — has shown absolutely no appetite for upsetting markets. After months of promising to hike rates before the end of the year, the FOMC waited until futures had priced in the near certainty of a move, despite a year that featured, if anything, a steadying at best and an outright weakening at worst in economic data.

With the past as prologue, the idea that the Fed would surprise markets with a rate increase seems far-fetched.

"I'm sort of in a dump-the-dots mode," Diane Swonk, chief economist at Mesirow Financial, told CNBC after the December FOMC meeting. "I think that could be the Achilles' heel that they will have to deal with in communications going forward."

Indeed, the dots have seemed increasingly irrelevant as time has gone by through the days of zero interest rate policy. For the better part of the past two years FOMC members have been well ahead of market expectations for the pace of hiking.

It's become clear that the financial markets win that argument every time.

Read MoreFair? Banks hike prime rates, but not deposit rates

"They've been pretty transparent so far as to what they're going to do. I don't see them wavering from that," said J.J. Kinahan, chief market strategist at TD Ameritrade. "Think back to October. The futures market was pricing in a pretty big probability for a while, then shifted. At the end of the day, they matched up pretty well."

What's ahead, then, likely is a Fed that professes data dependency but which will continue to be market dependent as well.

"People should expect from this new Fed a level of direct and frankly honest communication about the complexity of the world we're in and the futility and mistake of looking for easy and simple patterns," said Zachary Karabell, head of global strategy at Envestnet. "This is clearly a Fed ... that is determined to treat the world like grown-ups."