This is the next-to-last event of the season on the LPGA Tour and Sorenstam has said this will be her final year on the circuit.
In recent weeks, Sorenstam has backed off her comment that she will be retiring, saying she wants to take some time away from golf.
Sorenstam was tied with Karen Stupples, Nicole Castrale, Hee-Won Han, Brittany Lang, Seon-Hwa Lee, Angela Stanford and Yani Tseng atop the crowded leader board.
Ochoa, who replaced Sorenstam as the world's top-ranked player, settled for a 73 and was tied for 24th place.
"Unfortunately, I didn't play the way I wanted to," Ochoa said. "I'm going to try and make a lot of birdies tomorrow."
Ochoa is hosting this 36-player event for the first time.