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tokens: we cannot trust them since these very large parameters produce synthetic profiles with a significant portion being out of the observed spectral range (Figure 15 ). The inversion code combined a strongly shifted two-lobed Stokes V profile with an unshifted one to recreate the observed three-lobed Stokes V profile, without any information about what the profiles would look like outside the spectral range. Figure 14. Right panels: observed and best-fit Stokes profiles (black and red, respectively). Left panels: atmospheric parameters inferred for the fast (blue) and the slow components (magenta) from the inversion. The filling factor of the fast component is shown in the lower left corner of the top panel. Figure 15. Synthetic profiles resulting from the fast and the slow atmospheres (blue and magenta lines, respectively) plotted in Figure 14 . The gray line shows the blue one multiplied by a scale factor for better visibility. As a reference, the observed and best-fit profiles are also shown here in black and red, respectively. The dotted vertical lines delimit the observed spectral range. To solve this situation, we decided to repeat the inversion considering as initial models the atmospheric stratifications obtained from a nearby pixel unaffected by this problem whose Stokes V profile is similar. The results are shown in Figure 16 . Although the fit is not as good as in the previous inversion, it is still reasonable. The inversion now finds strongly shifted and reversed two-lobed Stokes V profile, together with an unshifted profile, whose combination reproduces the observed spectral signatures, being a more reliable solution. Figure 16. Best-fit profiles and atmospheric parameters inferred from an inversion of the same pixel as in Figure 14 considering as initial models the results from a close pixel with a similar Stokes V profile. The layout is the same as in Figure 14 . Although these structures resemble Evershed clouds (e.g., Rimmele 1994 ; Shine et al. 1994 ; Cabrera Solana et al. 2006 , 2007 ), we do not find any indication of two velocity packets inside the patch traveling outward as a whole. In addition, Cabrera Solana et al. ( 2007 ) found that the two Evershed cloud packets have opposite magnetic polarities when they cross the sunspot border, which has not been found in our observations. A number of physical mechanisms are known to be able to drive supersonic flows in the penumbra, including siphon flows (Thomas 1988 ) and moving magnetic tubes (Schlichenmaier 2002 ). Both mechanisms might well explain our observations, but a detailed comparison is difficult because the theoretical results are based on idealized models that are often simplistic and do not consider the actual conditions of the penumbra (in particular, the fact that it is a stratified atmosphere with temperatures, pressures, and magnetic fields varying both vertically and horizontally). The 3D radiative MHD simulations of Rempel ( 2012 ), on the other hand, show