  Early-time observations of the Type II supernovae (SNe) 2013cu and 2013fs
have revealed an interaction of ejecta with material near the star surface.
Unlike the Type IIn SN2010jl, which interacts with a dense wind for ~1yr, the
interaction ebbs after 2-3d, suggesting a dense and compact circumstellar
envelope. Here, we use multi-group radiation-hydrodynamics and
non-local-thermodynamic-equilibrium radiative transfer to explore the
properties of red supergiant (RSG) star explosions embedded in a variety of
dense envelopes. We consider the cases of an extended static atmosphere or a
steady-state wind, adopting a range of mass loss rates. The shock-breakout
signal, the SN radiation up to 10d, and the ejecta dynamics are strongly
influenced by the properties of this nearby environment. This compromises the
use of early-time observations to constrain Rstar. The presence of narrow lines
for 2-3d in 2013fs and 2013cu require a cocoon of material of ~0.01Msun out to
5-10Rstar. Spectral lines evolve from electron-scattering to Doppler broadened,
with a growing blueshift of their emission peaks. Recent studies propose a
super-wind phase with a mass loss rate from 0.001 up to 1Msun/yr in the last
months/years of the RSG life, although there is no observational constraint
that this external material is a steady-state outflow. Alternatively,
observations may be explained by the explosion of a RSG star inside its complex
atmosphere. Indeed, spatially resolved observations reveal that RSG stars have
extended atmospheres, with the presence of downflows and upflows out to several
Rstar, even in a standard RSG like Betelgeuse. Mass loading in the region
intermediate between star and wind can accommodate the 0.01Msun needed to
explain the observations of 2013fs. A puzzling super-wind phase prior to
core-collapse may be therefore superfluous [Abridged].
