Ochoa made two eagles and had a three-stroke lead halfway through the weather-disrupted tournament. After play was suspended because of lightning Friday, Ochoa picked up where she left off with birdies on two of her remaining four holes on Saturday morning.
She shot an 8-under 64 in the second round, and was at 11-under 133 through 36 holes.
Catriona Matthew was three shots back at 8-under 136. Norway's Suzann Pettersen, who completed her round on Friday, was four back at 7-under.
Sorenstam trailed Ochoa by seven strokes after a 4-under 68 in the second round.
'I think I'm in good shape,' said Sorenstam, who's trying to win the tournament for the third time in four years. 'I look forward to the weekend.'
There were six golfers between Sorenstam and Ochoa. But Sorenstam's pursuit of Ochoa made a potentially intriguing story line for the final two rounds.
Both Sorenstam and Ochoa were standout golfers at the University of Arizona, about 100 miles away. And Ochoa last year broke Sorenstam's five-year streak as the LPGA Tour's player of the year.
Both women seem to thrive at Superstition Mountain.
On Friday, Sorenstam had five birdies and only one bogey. It was her eighth round (of 14) in the 60s on the course carved out of the Superstition foothills.
'I hit some beautiful iron shots,' Sorenstam said.
So did Ochoa. She eagled the par-4 sixth hole, holing a 6-iron from 165 yards. On the par-5 13th, she hit her second shot within 10 feet of the green and holed a 30-foot wedge shot.
'I'm hitting my irons really good,' she said.
Ochoa, who opened with a 69 on Thursday, finished tied for third at Superstition Mountain in 2004 and then lost to Sorenstam in that playoff in 2005.
'I never think about what happened in 2005,' Ochoa said. 'This is a new year, a new tournament.
'Arizona means a lot to me,' Ochoa said. 'I feel really comfortable playing out here. All the people give me warm backing and are cheering for me. This would be a special tournament to win.'
On Friday, Ochoa teed off in the afternoon, after the weather cleared, and sensed an opportunity to attack the course. As she made the turn, she saw that she had tied Pettersen for the lead.
'I was 7 under making the turn, and I just kept looking at the leaderboard,' Ochoa said. 'I was the one who still has nine holes to go. So I'd better try to get ahead of everybody.'
Play was suspended because of darkness for the second day in a row. On Thursday, rain and lightning stopped the tournament for about two hours, forcing 72 players to finish the first round on Friday morning.
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