Jeremy Siegel's forecast for the financial markets

One well-known market bull believes that stocks are set to keep climbing, but is looking for a key catalyst to drive further market growth.

Jeremy Siegel predicted that equities could jump by as much as 15 percent in the second half of the year. He reinforced his outlook,by saying that strong earnings season is needed or the market could see its wings clipped.

"I think we need an earnings acceleration If we really want to get this market moving," said Siegel. "But in the presence of a 1.5 percent 10-year [Treasury note yield], low rates, the Fed [giving] at most one increase [this year] and the dividend yield on the stock market being over 2 percent, people are saying, 'Hey, it's not bad being here.'"

Siegel sees the S&P 500 headed above 2,300 this year, which means that the index would have to rise about another 6 percent based on Wednesday's level of 2,177.34. But Siegel is also looking at possible rallies in the Nasdaq and the Dow to take the markets higher.

More specifically, Siegel believes that if a catalyst like earnings appears to drive growth, the Dow could beat its intraday record of 18,622.01, which the index set in late July.

"We'll get over 19,000, that isn't much from now [and] it could reach near 20,000 if we get a meaningful acceleration in GDP and earnings growth, [along with] getting oil back towards $50 to $55," said Siegel. "That would revive the energy sector, which has been a big drain on earnings."