To estimate icing conditions in clouds, an icing index from a numerical model may be a useful forecast tool although you have to be aware that such an index will not solve the whole forecast problem. A new icing algorithm was developed by the Swedish group. The algorithm takes into account, directly or indirectly, all the main meteorological variables for icing; temperature, amount of liquid water, size of the droplets. The vertical velocity was chosen as a substitute for the droplet size, which is not available from the numerical models. The index has been operational as a post-processed product from the Swedish HIRLAM model since 1999. It has proved to be a good forecast tool for icing in clouds, especially in situations with lows, fronts and orographical updraft.