Lorde, the New Zealand singer who enjoyed phenomenal success while still a teenager, celebrated her 20th birthday Monday by announcing a new album that will explore becoming an adult.

The long-awaited follow-up to her blockbuster 2013 debut album "Pure Heroine" will be out soon, she said, without giving a date.

"Writing 'Pure Heroine' was my way of enshrining our teenage glory, putting it up in lights forever so that part of me never dies, and this record -- well, this one is about what comes next," she wrote on Facebook around midnight in New York, where she has been recording the album.

Turning 20, "I'm not a kid any more, and more and more I'm realizing that the weirdness of those Mylar balloons is going to be okay," she added, referring to the shiny balloons given for celebrations.

Having written songs since age 13, Lorde became an international sensation with her song "Royals," a mocking look at the pursuit of material wealth that won the Grammy for Song of the Year in 2014.

Lorde, whose real name is Ella Yelich-O'Connor, has managed to avoid the excesses and tabloid headline-generating lifestyle that are notorious among child stars.

She made "a very deliberate choice to withdraw from public life" over the past year, she wrote, and enjoyed the greater anonymity for the most part.

"I started to discover in a profound, scary, blood-aching way who I was when I was alone, what I did when I did things only for myself."

Saying little about her forthcoming album, Lorde boasted its lyrics were "the best I've written in my life."

"The party is about to start," she wrote. "I am about to show you the new world."