The paper presents the results of numerical simulations of a combustion process for a pure hydrogen jet in the atmosphere of oxygen and water vapor. The research was performed using Large Eddy Simulations (LES) combined with Conditional Moment Closure (CMC) model and included the analysis of auto-and forced (spark) ignition, flame development and flame propagation. In the configuration analyzed in the study, the fuel jet issues into a hot co-flowing oxidizer stream (O-2/H2O). We considered two different co-flow temperatures, 1030 K and 1045 K, and various oxidizer compositions with H2O mass fraction over the range of Y (H2O) = 0.1 - 0.9 and with Y-O2 = 1 - Y-H2O. The analyses were carried out with assuming constant 30% excess of the mass flow rate of oxygen relative to the hydrogen. It was found that: (i) the auto-ignition process occurs only for a low content of H2O in the co-flow Y-H2O <= 0.5), (ii) and is additionally determined by its temperature; (iii) depending on O-2/H2O proportion the flames stabilizes as attached or lifted. By alteration of Y-H2O in the oxidizer, the maximum flame temperature and the lift-off height (L-H) can be changed in the range of 1500K -> 3000K and L-H = 0 -> 11 jet diameters, respectively. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.