Fantasy novel with an aztec theme

I think I read this book in the late 90s. It could have been adult or YA. It had an urban fantasy setting with fairly modern technology, but with an Aztec feel to it and a strong focus on prophecy.

The main character's name is something like Quincey Coatl (it wasn't Quetzalcoatl, but did sound similar). He works as a weather prophet, but has no prophetic abilities. He's terrified of anyone finding this out and losing his job, so he attempts to predict the weather by observing patterns. It turns out that this scientific approach is far more accurate than the prophecies of the other employees, so he gets a reputation as a really good prophet.

Later on in the plot, he somehow becomes known as the self-fulfilling prophet, with everyone convinced that anything he prophesises will come true.