  Star formation is underway in the W49N molecular cloud (MC) at a high level
of efficiency, with almost twenty ultra-compact (UC) HII regions observed thus
far, indicating a recent formation of massive stars. Previous works have
suggested that this cloud is undergoing a global contraction. We analyse the
data on OH masers in the molecular cloud W49N, observed with the VLBA at the
1612, 1665, and 1667 MHz transitions in LCP and RCP with an aim to study the
global kinematics of the masers. We carried out our study based on the
locations and observed velocities of the maser spots.
  The velocities were fitted to the straight line of V$_{obs}$-V$_{sys}$ versus
d$_{(\alpha, \delta)m}$, resulting in V$_{ftd}$. The difference between the
fitted values and those obtained from observations is $\Delta $V. The
V$_{obs}$-V$_{sys}$ velocity shows a gradient as a function of the distance to
($\alpha, \delta$)$_{m}$, where the closer spots have the largest velocities.
Spots with similar velocities are located in different sectors, with respect to
($\alpha, \delta$)$_{m}$. Then, we assumed that the spots are moving towards a
contraction centre (CC$_{OH}$), which is at the apex of a CONUS. We also
assumed that the distance of each spot to CC$_{OH}$ is d$_{cc}$ and that they
fall with a velocity V$_{CC}$, with the total velocity being V$_{Tot}$. Using
this velocity, we estimated the free-fall velocity. The observed dispersion
with respect to the global trend against $d_{cc}$, shows a maximum at 0.12 pc,
with a decay from 0.12 to 0.19 pc, which is faster than that taking place
between 0.19 and 0.42 pc. Based on $V_{tot}$ an inner mass of M$_{inn}$=2500
$M_{\odot}$ was estimated.The velocities of the OH spots at W49N, together with
their positions respect $(\alpha, \delta)_m$, make it possible to trace a
global kinematics, which seems to be due to a subcollapse in the W49N molecular
cloud.
