  Gas morphology and kinematics in the Milky Way contain key information for
understanding the formation and evolution of our Galaxy. We present a high
resolution hydrodynamical simulation based on a realistic barred Milky Way
potential constrained by recent observations. Our model can reproduce most
features in the observed longitude-velocity diagram, including the Central
Molecular Zone, the Near and Far 3-kpc arms, the Molecular Ring, and the spiral
arm tangents. It can also explain the non-circular motions of masers obtained
by the recent BeSSeL2 survey. The central gas kinematics are consistent with a
mass of $6.9\times10^8\; {\rm M}_{\odot}$ in the Nuclear Stellar Disk. Our
model predicts the formation of an elliptical gaseous ring surrounding the bar,
which is composed of the 3-kpc arms, Norma arm, and the bar-spiral interfaces.
This ring is similar to those "inner" rings in some Milky Way analogs with a
boxy/peanut-shaped bulge. The kinematics of gas near the solar neighbourhood
are governed by the Local arm, which is induced by the four major stellar
spiral arms. The bar pattern speed constrained by our gas model is $37.5-40\;
{\rm km}\;{\rm s}^{-1}\;{\rm kpc}^{-1}$, corresponding to a corotation radius
of $R_{\rm CR}=6.0-6.4\;{\rm kpc}$. The rotation curve of our model rises
gently within the central $\sim5\;{\rm kpc}$, which is significantly less steep
than those predicted by modern zoom-in cosmological simulations such as Auriga.
