  Filamentary structures are often identified in column density maps of
molecular clouds, and appear to be important for both low- and high-mass star
formation. Theoretically, these structures are expected to form in regions
where the supersonic cloud-scale turbulent velocity field converges. While this
model of filament formation successfully reproduces several of their properties
derived from column densities, it is unclear whether it can also reproduce
their kinematic features. We use a combination of hydrodynamical, chemical and
radiative transfer modelling to predict the emission properties of these
dynamically-forming filaments in the $^{13}$CO, HCN and N$_2$H$^+$ $J=1-0$
rotational lines. The results are largely in agreement with observations; in
particular, line widths are typically subsonic to transonic, even for filaments
which have formed from highly supersonic inflows. If the observed filaments are
formed dynamically, as our results suggest, no equilibrium analysis is
possible, and simulations which presuppose the existence of a filament are
likely to produce unrealistic results.
