H I covering fraction (﹩{{ \mathcal L }}_{HI}﹩) as a function of impact parameter for the “smoothed” (solid) and “filtered” (dashed) moment-0 maps shown in Figures 2 and 3 at 20 Mpc. As expected, the curve for Maelstrom does not change significantly, as there is little diffuse material that is filtered out. For both Blizzard and Cyclone, the filtered curve is shifted to the left by a few kpc due to diffuse material being filtered out. Covering fractions are calculated in 2 kpc thick annuli centered on the given impact parameter.