So “16.4 mph north” is sufficient.
No, it’s not. “North” is a two dimensional direction on the surface of the earth. But we live, and can throw babies, in three dimension. Therefore you need to specify the inclination as well. “56 furlongs per minute, north, 0.3 radians” would suffice.



Or 5.999… It’s equal to 6 but it appears to have a much more impressive decimal expansion