The throw is the longest outdoor performance in the world for the year, improving the previous best - set by Adams at the New Zealand champs - of 20.37 metres by more than half a metre and further than the double Olympic gold medallist threw to win at the London Olympic Games.
Adams also has an indoor best of 20.75 metres for 2013 set at the Shot in the City event in the Cloud on Auckland's waterfront.
Her closest rivals this year, American Michelle Carter and German Christina Schwanitz, have thrown personal bests of 20.24m and 20.20 metres respectively.
Adams, whose brother Steven faces a big day in the NBA draft in New York today, had an excellent series with 20.15m, 20.55m, 20.30m, 20.64, foul and the final effort of 20.88m.
Her next competition will be the Paris Diamond League meeting on July 6.
Meanwhile, javelin thrower Stuart Farquhar placed fourth with a second round toss of 77.64m, which he followed with four fouls.
Farquhar has yet to reach the form he struck early last year when he threw a personal best of 86.31m in Japan.
He competes again on Sunday at the Birmingham Diamond League meeting.
