'Are you able' is an expression about the ability to do something. I can't think of a single instance where it would be dependent on circumstances. In a job interview, you might be asked several questions along these lines: are you able to do this, are you able to do that? If we wanted to know something about circumstances, we would ask a completely different question: are you at a computer now? do you have access to a computer?
If there were more context perhaps, but 'are you able' is a perfectly valid translation for 'umis?'