  A jet is simulated on the background of a galactic wind headed by a radiative
bow shock. The wind shell, which is due to the radiative bow shock, is
effectively destroyed by the impact of the jet cocoon, thanks to
Rayleigh-Taylor instabilities. Associated strong HI absorption, and possibly
also molecular emission, in high redshift radio galaxies which is observed
preferentially in the smaller ones may be explained by that model, which is an
improvement of an earlier radiative bow shock model. The model requires
temperatures of $\approx 10^6$ K in the proto-clusters hosting these objects,
and may be tested by high resolution spectroscopy of the Ly$\alpha$ line. The
simulations show that -- before destruction -- the jet cocoon fills the wind
shell entirely for a considerable time with intact absorption system.
Therefore, radio imaging of sources smaller than the critical size should
reveal the round central bubbles, if the model is correct.
