Atmosphere stratification of one of the pixels of the umbral flash with supersonic velocities. From top to bottom: Temperature T, line-of-sight velocity normalized to the local sound speed (i.e. line-of-sight Mach number) v_los/c_s, logarithm of density log ρ, and logarithm of gas pressure log P_g. Bottom axis and red lines represent the physical parameters as a function of the optical depth scale log τ_c, whereas the upper axis and blue lines represent the physical parameters as a function of geometrical height z. We note the continuum (log τ_c = 0) is formed at around z ≈ 0.2 Mm above the lowermost boundary of the domain. Error estimations inferred from the Stokes inversion are presented for the temperature and velocity as shadowed areas. The horizontal dashed line represents the limit at which the line-of-sight velocity becomes supersonic.