The weather was getting rough again, she wrote.
"The wind is beginning to pick up. It is back up to 20 knots and I am expecting that by midnight tonight I could have 35-50 knots with gusts to 60 so I am off to sleep before it really picks up," she wrote.
Abby's goal at the outset of her trip, to become the youngest sailor to pull off a solo nonstop circumnavigation, ended in April, when she was forced to stop in South Africa because her autopilot malfunctioned.
In a June 2 report titled "How Young Is Too Young?," "20/20" described Sunderland's circumnavigation attempt.
"I am definitely nervous," Abby told "20/20." "People say you shouldn't be nervous if you are really ready to do this. But I understand [the] ocean, and I understand how dangerous what I am doing actually is, and I understand how careful I need to be out there."
Late last year, Abby began talking publicly about her plan to circumnavigate the globe by herself in a 40-foot boat. It would be, she said, the fulfillment of a dream she sprang on her parents when she was 13.
Laurence and MaryAnne Sunderland helped their daughter to prepare for the attempt.
"Could there be a tragedy?" MaryAnne Sunderland said. "Yeah, there could be. But there could be a tragedy on the way home tonight, you know, or driving with her friends in a car at 16. You minimize the risks."
"You arm them with the coping skills," Laurence Sunderland said. "And then you pray."
Not everyone who heard of Abby's plan has been as supportive.
"Child abuse. Child endangerment," said T.J. Simers, a sports columnist for the Los Angeles Times and father of two grown daughters. "I just don't understand the idea of risking life. This kid's going to be out there all by herself. Death is a possibility. Bad weather. Are you kidding me? Who's responsible for this? She's a kid."
Abby is not the first talented teenager to dream of sailing around the world solo. In 1999, a 17-year-old named Jesse Martin accomplished just that. Yet while at sea, the teen struggled with loneliness and life-threatening storms that left him emotionally devastated.
But Martin witnessed some unforgettable sights along the way -- and made it safely. His adventures were chronicled in the documentary "Lionheart."
"If I never came back it would not have been a tragedy ... a tragedy would be someone who dies at 80 and spent 80 years not being satisfied," Martin said in the documentary. "I was out there doing what I wanted."
Abby set sail Jan. 23 from Marina del Rey, Calif. Her parents watched as their teenage daughter faded into the horizon.
Later, via a Skype interview from her boat, Abby would recall her emotions that day.
"It was completely overwhelming," she said. "I mean, there was people everywhere, and boats, and all this noise and commotion and stuff. And then all of a sudden it just leaves, and you're the only person out there."
But Abby wasn't completely alone. While at sea, she talked with her mother twice a day, blogged her latest news and kept up her page on Facebook. One of her friends was Jessica Watson, a 16-year-old Australian also in the process of sailing solo around the world.
"I just love, you know, going out and doing something and having to rely on yourself -- you know, it's up to me," Jessica said in an ESPN documentary.