Production control must have accurate models for the prediction of tundish temperature to meet increasing demands on control and production rate in continuous casting. The models have to be simple. They must also include the effect of variations in steel flow and mixing, including shortcut flows from the inlet stream towards the outlet end. To meet this demand, a tank in series model was designed, which also included the effect of dynamic shortcut flows. The model has been verified by data from experiments with chemical tracers in a 14 tonne straight tundish. The tracers have been added both in the ladle and close to the inlet end in the tundish and the response in the steel entering the mould has been died. The data seem to confirm that there is a different distribution of the steel flow in the period shortly after the ladle change. The difference could be explained either as shortcut flows caused by buoyancy or by increased stirring. It is possible to choose a configuration of tanks that allows simulation of both the transient behaviour at ladle change and the steady state conditions during the main part of the casting by changing the adjustable parameters for the shortcut flow without changing the configuration of tanks.