A new version of the Weiland model has been used in predictive JETTO simulations of toroidal rotation. The model includes a self-consistent calculation of the toroidal momentum diffusivity (χϕ) which contains both diagonal and non-diagonal (pinch) contributions to the momentum flux. Predictive transport simulations of JET H-mode, L-mode and hybrid discharges are presented. It is shown that experimental temperatures and toroidal velocity were well reproduced by the simulations. The model predicts the ion heat diffusivity (χi) to be larger than the momentum diffusivity and it gives Prandtl numbers (Pr = χϕ/χi) between 0.1 and 1. The Prandtl numbers are often, depending on the plasma conditions, predicted to be significantly smaller than unity. This is in accordance with experimental findings.