  Early observations of supernovae (SNe) indicate that enhanced mass loss and
pre-SN outbursts may occur in progenitors of many types of SNe. We investigate
the role of energy transport via waves driven by vigorous convection during
late-stage nuclear burning of otherwise typical $15 \, M_\odot$ red supergiant
SNe progenitors. Using MESA stellar evolution models including 1D
hydrodynamics, we find that waves carry $\sim \! 10^7 \, L_\odot$ of power from
the core to the envelope during core neon/oxygen burning in the final years
before core collapse. The waves damp via shocks and radiative diffusion at the
base of the hydrogen envelope, which heats up fast enough to launch a pressure
wave into the overlying envelope that steepens into a weak shock near the
stellar surface, causing a mild stellar outburst and ejecting a small
($\lesssim 1 \, M_\odot$) amount of mass at low speed ($\lesssim \! 50 \, {\rm
km}/{\rm s}$) roughly one year before the SN. The wave heating inflates the
stellar envelope but does not completely unbind it, producing a non-hydrostatic
pre-SN envelope density structure different from prior expectations. In our
models, wave heating is unlikely to lead to luminous type IIn SNe, but it may
contribute to flash-ionized SNe and some of the diversity seen in II-P/II-L
SNe.
