Comparing forecast accuracy

For many years we have verified our forecasts by comparing forecasts of mean sea-level pressure with subsequent model analyses of mean sea-level pressure. These comparisons are made over an area covering the North Atlantic; most of western Europe, and north-eastern parts of North America. From this long-term comparison an average forecast error can be calculated.

The graph shows how many days into a forecast period this average error is reached compared to a baseline in 1980. This graph shows that a four-day forecast today is more accurate than a one-day forecast in 1980.