A conditional sampling technique was designed and employed to determine the ensemble‐averaged flow structures in the developing region of a symmetric wake (r=1.0) and an unsymmetric wake (r=0.5). It was found that at a velocity ratio of 0.5 the large scale structure, which was observed from a reference frame traveling with its phase speed, is initially confined in the high‐speed stream, elongated in the stream direction, and is shaped elliptically. As the flow convects downstream it grows in the cross‐stream direction, as well as tilting toward the wake center, and then evolves into a nearly circular shape. Results for a velocity ratio of 1.0, corresponding to the case of a 2‐D wake flow, show that two rows of counter‐rotating vortices develop in two streams originating in the linear instability region. Similar to the case forr=0.5, these vortices grow, as well as tilt, when the flow convects them downstream. However, the growth rate of these flow structures is slower than that of the case forr=0.5.