The direction of the MBE (the most active part of the MCS) is dependent on the direction of the low-level jet (Corfidi et al., 1997) and on the position of the most moist and unstable air relative to the MCS.
Direction of low-level jet
Systems with propagation vectors between 0-120 degrees have been plotted between 360 and 480 degrees
The direction of propagation is in the opposite direction of the low-level jet. This may be why MCCs tend to track to the right of the mean wind.
Direction of MBE propagation