There are always errors in any prediction of the future, and weather forecasts are not an exception. The errors increase as the forecasts get longer, so the shortest forecasts are usually the most accurate, even if only traditional forecast methods are used. Nowcasting adds new methods to the mix that are applicable only for the immediate future, making the shortest forecasts even more accurate.
Since weather phenomena move around the world, weather forecasts need to take the entire Earth's atmosphere into consideration. To provide a concrete example, the weather in London next weekend can be affected by what happens to the weather in Mexico today. To cover the global scale, Foreca uses global weather models such as the ECMWF. Since global forecast models are calculated every six or twelve hours, and the calculations take several hours, they are already a little out-of-date at the time of publication. There are also small-scale weather phenomena which the coarse global model grid cannot represent.
The ECMWF model is universally recognized to be the most accurate global forecast model, and it often beats local area weather models in flat terrain. The ECMWF data is of fantastic quality and is usable as such. But to further enhance the forecasts, Foreca uses multiple local weather models and post-processing techniques to make its own Foreca Weather Model even more accurate. On top of that, Foreca Nowcasting can add further improvement for the crucial first hours.