Figure 5.5Errors (root mean square differences of forecasts of surface pressure
compared with analyses) of UK Meteorological Office forecasting models for the
north Atlantic and Western Europe since 1966 for 24-h, 48-h and 72-h forecasts.
Note that 1 hPa=1 mbar.
Figure 5.6Illustrating potential improvements in forecast skill if there were
better data or a better model. The ordinate (vertical axis) is a measure of the
error of model forecasts (it is the root mean square differences of forecasts of the
500 hPa height field compared with analyses). Curve (a) is the error of 1990 UK
Meteorological Office forecasts as a function of forecast range. Curve (b) is an
estimate showing how, with the same initial data, the error would be reduced if
a perfect model could be used. Curve (c) is an estimate showing the further
improvement which might be expected if near-perfect data could be provided
for the initial state. After a sufficiently long period, all the curves approach a
saturation value of the average root mean square difference between any
forecasts chosen at random.