The role of longitudinal flow asymmetries due to Rossby wave breaking in creating a spatial and temporal "phase-locking" of inertial instability events in the middle atmosphere is explored. A decade-long climatology using UKMO assimilated analyses is used to juxtapose the evolution of inertial instability and Rossby wave breaking in longitude, latitude, altitude and time. Our results indicate a poleward-eastward "channel" of preferred inertial instability frequency in both winter hemispheres that agrees well with the few previously published case studies. These results also reveal that inertial instability is not limited to the equatorial region and can occur in this channel poleward into the high latitudes. The reliability of these conclusions is defended by cross-checking the results of the climatology with individual case studies from the period.