How to handle dependent/linked variables in regression analysis

I'm running an analysis (using Minitab) that includes data for wind speed and direction. On the face of it it seems to me that these should end up as one coefficient as 10mph N wind should have a different effect than a 10mph S wind and the output gives equations that only look at speed and direction separately. Treating the direction as categorical sort of addresses the question but is a little clunky.

Any thoughts would be appreciated.