[1] The correlation between unforced variability in the latitude of the edge of the Hadley cell (Φ HC ) and latitude of the surface westerlies (Φ EDJ ) is examined using a simplified moist general circulation model (GCM) and a suite of state of the art GCMs. The correlation can be determined by the time-mean separation of the two features. When the separation is small, there is a positive correlation, and as the separation between them increases, the correlation reduces. In the simplified model, a weak negative correlation emerges at large separations.[2] The location of the anomalous meridional mass flux associated with variations in the latitude of Φ EDJ , relative to the climatological Hadley cell position, determines the extent to which Φ HC is influenced by changes in Φ EDJ . Changes in the latitude of Φ EDJ are driven by anomalous eddy momentum flux convergence, and these are approximately balanced by the Coriolis torque on the meridional flow, as expected under quasi-geostrophic scaling. Under changing time-mean climates, the anomalous flow associated with Φ EDJ variability translates location so that it is approximately fixed relative to the time-mean Φ EDJ . This means that the influence of Φ EDJ variability on Φ HC varies as a function of the time-mean separation of the features.[3] Initial indications are that the same causal relationship holds in a suite of state of the art GCMs and that this explains the seasonal variation in the correlation between Φ HC and Φ EDJ . Citation: Kidston, J., C. W. Cairns, and P. Paga (2013), Variability in the width of the tropics and the annular modes,