This is 1986 in Seattle after all, and I feel the capsize in my chest like a rowboat caught in a storm, and when they raise the curtain, I will be the girl in the back dressed like a boy in a borrowed karate suit, taller than everyone but not quite so nimble or quick.
The author creates imagery by creating a simile. The simile compares her nervousness to a rowboat caught in a storm. This allows the reader to picture the moment and feel what she is feeling.