How do people changing fields after PhD overcome competition with "locals"?
Some of my best hires have had virtually no direct or recent experience in HPC, but have demonstrated a number of other extremely desirable features including:


A passion for learning and doing
A clear track record of success in their related area (including publishing, mentoring, grant-writing, etc.).
An strong awareness of their own limitations in the field and a plan for dealing with them
A strong understanding of our needs based on researching our mission, goals, website, etc. and a plan for how they fit into that.


Based on this, I've taken a flyer on a researcher or two who wasn't a perfect fit but was too passionate, engaging, and obviously successful to pass up. A ridiculously strong reference is also helpful.