  We employ the earlier published proper motions of the newly discovered Antlia
2 dwarf galaxy derived from Gaia data to calculate its orbital distribution in
the cosmologically recent past. Using these observationally motivated orbits,
we calculate the effect of the Antlia 2 dwarf galaxy on the outer HI disk of
the Milky Way, using both test particle and Smoothed Particle Hydrodynamics
simulations. We find that orbits with low pericenters, $\sim$ 10 kpc, produce
disturbances that match the observed outer HI disk perturbations. We have
independently recalculated the proper motion of the Antlia 2 dwarf from Gaia
data and found a proper motion of $(\mu_{\alpha}cos\delta, \mu_{\delta}) =
(-0.068,0.032) \pm (0.023,-0.031)~\rm mas/yr$, which agrees with results from
Torrealba et al. (2019) within the errors, but gives lower mean pericenters,
e.g., $\sim$ 15 kpc for our fiducial model of the Milky Way. We also show that
the Sagittarius dwarf galaxy interaction does not match the observed
perturbations in the outer gas disk. Thus, Antlia 2 may be the driver of the
observed large perturbations in the outer gas disk of the Galaxy. The current
location of the Antlia 2 dwarf galaxy closely matches that predicted by an
earlier dynamical analysis (Chakrabarti \& Blitz 2009) of the dwarf that drove
ripples in the outer Galaxy, and, in particular, its orbit is nearly coplanar
to the Galactic disk. If the Antlia 2 dwarf galaxy is responsible for the
perturbations in the outer Galactic disk, it would have a specific range of
proper motions that we predict here; this can be tested soon with Gaia DR-3 and
Gaia DR-4 data.
