Dynamical models of strongly irradiated gas-giant atmospheres exhibit a range of behavior, the nature of which depends on both the adopted parameters and the adopted numerical model. Discerning the correct choice of physical parameters and modeling philosophy can be difficult. Here, I present a series of wavelength-dependent transmission spectra for the giant planet HD209458b based on 3D radiative hydrodynamical models for a range of kinematic viscosities. While flow patterns and temperature distributions can vary significantly, disk-averaged phase curves mask much of this information. Transmission spectra, on the other hand, probe the day-night transition where advective contributions dominate and differences are often most pronounced. Transmission spectra illustrate noticeable changes, especially when comparing the differences between transmission spectra of eastern and western hemispheres, as might be seen during ingress and egress.