\label{fig:example_envelope}
Wave envelope (calculated from the 30-day running mean, 500 hPa meridional wind) for 22 May 1986 and 29 July 2006. The black contours show the corresponding 500 hPa streamfunction zonal anomaly (dashed contours indicate negative values and the contour interval is $5 \times 10^6 \: m^2 s^{-1}$). Wavenumbers 1-9 were retained and the 54.75$^{\circ}$S latitude band is indicated with a gray dashed line for ease of comparison with Figure \ref{fig:example_hilbert}. 