(Reuters) - Japan's Haru Nomura produced a strong finish on the tougher back nine to take a three-shot lead after the second round at the Swinging Skirts LPGA Classic in San Francisco on Friday.
The 23-year-old bided her time with 11 consecutive pars, before rolling in 12-foot birdies at the next two holes as she signed for a two-under-par 70 to move clear of the field in a testing breeze at the Lake Merced Golf Club.
"I keep my patience, so I'm so relaxed, and a couple putts in, and that's it," Nomura, who won the Women's Australian Open in February, said after reaching the halfway mark on a nine-under 135 total.
Australian teenager Minjee Lee, coming off a victory at the LOTTE Championship in Hawaii on Sunday, continued her strong form when she surged into a share of second with a bogey-free 65.
Lee was joined at six-under by overnight leader Ryu So-yeon (75) and Choi Na-yeon (70) of South Korea, with two-time defending champion Lydia Ko a further shot back after two late bogeys.
Ko, who turns 19 on Sunday, is seeking to become the youngest player to win an LPGA event for three consecutive years.
"I knew with the wind getting up it would be tough," Ko said after a one-under-par 71.
"The back nine played quite tough yesterday and kind of the same (today).
"I hit a few wayward shots but overall I played I played pretty solidly. My ball-striking wasn't too good on my back nine but hopefully we can get that sorted."
Ko played in the afternoon, while Lee endured the morning rain that abated for the late starters.
"I came off a really great win last week, so I should have a lot of confidence and momentum coming into this week too," Lee said.
"I just stayed patient, took advantage of the opportunities I had."
(Reporting by Andrew Both in Cary, North Carolina; Editing by John O'Brien)