  We present measurements of the azimuthal orientation {\theta}(t) and thermal
amplitude {\delta}(t) of the large-scale circulation (LSC) of turbulent
rotating convection within an unprecedented large Rossby number range 1<Ro<314.
Results of {\theta}(t) reveal persistent rotation of the LSC flow in the
retrograde direction over the entire Ro range. The rotation speed ratio remains
a constant of 0.13(${\pm}$0.01) for 10<Ro<70, but starts to increase with
increasing Ro when Ro>70. We identify the mechanism through which the mean
retrograde rotation speed can be enhanced by stochastic cessations in the
presence of weak Coriolis force, and show that a low-dimensional, stochastic
model provides predictions of the observed large-scale flow dynamics and
interprets its retrograde rotation.
