  We perform three-dimensional numerical simulations of surface flows on the
companion star in a semi-detached binary system and construct the corresponding
Doppler maps. The mass ratio of the binary system, $q=M_2/M_1$, considered here
is $q=0.05, 0.33, 0.5, 1, 2$, and 3. For all cases, we obtain the H-, L1-, and
L2-eddies, as found in our previous work, and confirm that the flow pattern
does not heavily depend on the mass ratio. We propose that this kind of problem
be dubbed ``{\it stellar meteorology}.'' The Doppler maps at the position of
the companion show a structure tilted towards clockwise direction and
presenting deviations from the critical Roche surface due to the L1-eddy and
the L2-eddy on the companion star. We apply our results to the Galactic
supersoft X-ray source RX J0019.8+2156 and try to attribute the low radial
velocity component of the emission lines of He II ${\lambda}4686$ observed
recently to the irradiated spot on the surface of the companion rather than
that of the white dwarf or the accretion disc. Based on the comparison between
the observations and our constructed Doppler map, we estimate the mass of the
companion star in RX J0019.8+2156 to be $\sim 2 M_{\odot}$ assuming the mass of
the white dwarf star to be around $0.6 M_{\odot}$.
