  We study the bifurcations of the large scale jets in the turbulent regime of
a forced shear flow using direct numerical simulations of the Navier-Stokes
equations. The bifurcations are seen in the probability density function (PDF)
of the largest scale mode with the control parameter being the Reynolds number
based on the friction coefficient denoted as $Rh$. As one increases $Rh$ in the
turbulent regime, the PDF of the large scale mode first bifurcates from a
Gaussian to a bimodal behaviour, signifying the emergence of reversals of the
large scale flow where the flow fluctuates between two distinct turbulent
states. Further increase in $Rh$ leads to a bifurcation from bimodal to
unimodal PDF which denotes the disappearance of the reversals of the largest
scale mode. We attribute the latter transition to the long-time memory that the
large scale flow exhibits related to low frequency $1/f^\alpha$ type of noise
with $0 < \alpha < 2$. We also demonstrate that a minimal model with 15 modes,
obtained from the truncated Euler equation, is able to capture the bifurcations
of the large scale jets exhibited by the Navier-Stokes equations.
