The behavior of azimuthal and radial velocity components of transient and free decaying rotating MHD flow in an annular gap of rectangular cross-section in an axial magnetic field has been studied. Experimental values of the velocity components of the flow were measured using a conductive anemometric system. Analysis of mean and oscillating characteristics was carried out using a continuous wavelet transformation based on the Morlet function. Signal scalograms were plotted and analyzed. It is shown that the dominating azimuthal mode m =1 of the velocity field develops over the whole volume in a transient regime and then decays exponentially with mean flow.