The dollar has enjoyed an incredible run over the past three months, rising 7 percent against the basket of currencies in the U.S. dollar index. And while currency expert Jens Nordvig says the move has legs, he believes that a continued dollar rise will now depend on strength against riskier emerging market currencies.

"I think we could see batches of enhanced U.S. dollar strength against select emerging market currencies, so that's going to be a little different from the composition of dollar gains we've seen in Q3," said Nordvig, global head of foreign exchange strategy at Nomura, on Tuesday's "Futures Now."

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The euro actually makes up 57.6 percent of the dollar index (often known by its index symbol, DXY) so recent weakness in the euro has certainly been a tail wind for that measure of dollar strength. But Nordvig predicts that the weakest currencies in the fourth quarter will be emerging market currencies like the South Korean won, the Malaysian ringgit and the South African rand.

As the Federal Reserve ends quantitative easing and looks to raise the fed funds rate, "that could be tricky for risk assets in emerging markets ... so some of those risky currencies could be very wobbly in the fourth quarter."

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Additionally, another massive quarter of gains for the dollar index simply looks unlikely.

"It was up almost 8 percent in the third quarter. If you just analyze, historically, the chances of getting two quarters of more than a 5 percent gain in the dollar index, it has happened only two times since the '70s, so it's very rare," Nordvig said. "That's just a word of caution for the ones who want to extrapolate, in a linear fashion, what we've seen in the last quarter."