With the stock market about to leave the summer behind, now is the time to buy, according to Jerry Castellini, president and chief investment officer of CastleArk Management.

In fact, he told CNBC on Thursday the market can move up 10 percent just to get back to "fuller valuation."

"I'm outright bullish," Castellini said on "Power Lunch."

He said market watchers have been focusing on the wrong things, such as emerging market weakness, politics and earnings that some worry may have reached their peak.

However, Castellini said the global economy is poised to turn.

"The consumption around the globe is now following all the liquidity that the central banks have provided these economies. And you're likely to see a continuing higher and higher expectation now for earnings kind of play out," Castellini said.

"That's what drives markets higher. And that's a surge that we still haven't seen the greatest part of, and you really want to be in front of that," he added. "You probably want to get in right now, and you want to get in before the [Labor Day] holiday."