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We derive accurate proper motions of the CH3OH 12 GHz masers towards theW3(OH) UCHII region, employing seven epochs of VLBA observations spanning atime interval of about 10 yr. The achieved velocity accuracy is of the order of0.1 km/s, adequate to precisely measure the relative velocities of most of the12 GHz masers in W3(OH), with amplitude varying in the range 0.3 - 3 km/s.Towards W3(OH), the most intense 12 GHz masers concentrate in a small areatowards the north (the northern clump) of the UCHII region. We have comparedthe proper motions of the CH3OH 12 GHz masers with those (derived fromliterature data) of the OH 6035 MHz masers, emitting from the same region ofthe methanol masers. In the northern clump, the two maser emissions emerge fromnearby (but likely distinct) cloudlets of masing gas with, in general, a rathersmooth variation of line-of-sight and sky-projected velocities, which suggestssome connection of the environments and kinematics traced by both maser types.The conical outflow model, previously proposed to account for the 12 GHz maserkinematics in the northern clump, does not reproduce the new, accuratemeasurements of 12 GHz maser proper motions and has to be rejected. We focus onthe subset of 12 GHz masers of the northern clump belonging to the "linearstructure at P.A. = 130-140 degree", whose regular variation of LSR velocitieswith position presents evidence for some ordered motion. We show that the3-dimensional velocities of this "linear distribution" of 12GHz masers can bewell fitted considering a flat, rotating disk, seen almost edge-on.

Revising the kinematics of 12GHz CH3OH masers in W3(OH)