  We present H-band interferometric observations of the red supergiant (RSG) AZ
Cyg made with the Michigan Infra-Red Combiner (MIRC) at the six-telescope
Center for High Angular Resolution Astronomy (CHARA) Array. The observations
span 5 years (2011-2016), offering insight into the short and long-term
evolution of surface features on RSGs. Using a spectrum of AZ Cyg obtained with
SpeX on the NASA InfraRed Telescope Facility (IRTF) and synthetic spectra
calculated from spherical MARCS, spherical PHOENIX, and SAtlas model
atmospheres, we derive $T_{\text{eff}}$ is between $3972 K$ and $4000 K$ and
$\log~g$ between $-0.50$ and $0.00$, depending on the stellar model used. Using
fits to the squared visibility and Gaia parallaxes we measure its average
radius $R=911^{+57}_{-50}~R_{\odot}$. Reconstructions of the stellar surface
using our model-independent imaging codes SQUEEZE and OITOOLS.jl show a complex
surface with small bright features that appear to vary on a timescale of less
than one year and larger features that persist for more than one year. 1D power
spectra of these images suggest a characteristic size of $0.52-0.69~R_{\star}$
for the larger, long lived features. This is close to the values of
$0.51-0.53~R_{\star}$ derived from 3D RHD models of stellar surfaces. We
conclude that interferometric imaging of this star is in line with predictions
of 3D RHD models but that short-term imaging is needed to more stringently test
predictions of convection in RSGs.
