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Longitude-velocity (l-V) diagrams of H I and CO gas in the inner Milky Wayhave long been known to be inconsistent with circular motion in an axisymmetricpotential. Several lines of evidence suggest that the Galaxy is barred, and gasflow in a barred potential could be consistent with the observed ``forbidden''velocities and other features in the data. We compare the H I observations tol-V diagrams synthesized from 2-D fluid dynamical simulations of gas flows in afamily of barred potentials. The gas flow pattern is very sensitive to theparameters of the assumed potential, which allows us to discriminate amongmodels. We present a model that reproduces the outer contour of the H I l-Vdiagram reasonably well; this model has a strong bar with a semimajor axis of3.6 kpc, an axis ratio of approximately 3:1, an inner Lindblad resonance (ILR),and a pattern speed of 42 km/s/kpc, and matches the data best when viewed from34\deg to the bar major axis. The behavior of the models, combined with theconstraint that the shocks in the Milky Way bar should resemble those inexternal barred galaxies, leads us to conclude that wide ranges of parameterspace are incompatible with the observations. In particular we suggest that thebar must be fairly strong, must have an ILR, and cannot be too end-on, with thebar major axis at 35\deg +/- 5\deg to the line of sight. The H I data exhibitlarger forbidden velocities over a wider longitude range than are seen inmolecular gas; this important difference is the reason our favored modeldiffers so significantly from other recently proposed models.Comment: 23 pages, 14 figures, 1 table, uses emulateapj and psfig, 640 kb.  Submitted to Ap

The Properties of the Galactic Bar Implied by Gas Kinematics in the Inner Milky Way