A time series in which the expected direction of movement, based on causal forces, corresponds with the direction of the statistical extrapolation. If they conflict, they are contrary series. Armstrong, Adya and Collopy (2001) discuss extrapolation for reinforcing series.

Armstrong, J. S., M. Adya & F. Collopy (2001), “Rule-based forecasting: Using judgment in time-series extrapolation,” in J. S. Armstrong (ed.), Principles of Forecasting. Norwell, MA: Kluwer Academic Press.