Temporal evolution of the 2006 radio flare in CTA 102 modeled with varying Doppler factor (black solid line) for t > 2006.0 and with the modifications of Björnsson & Aslaksen (2000) for the first two stages (red solid line). Both models fail to describe the 2006 flare (compare to Fig. 7); left: turnover frequency; right: turnover flux density. The lower panels show the residuum for the fits . The dashed black lines correspond to the time labels in Fig. 4 and indicate the extrema in the evolution.