Figure 1. A recent painting (from photographs) of the Norwegian scientist Vilhelm Bjerknes (1862-1951) (original in the Geophysical Institute, Bergen).
Figure 2. Lewis Fry Richardson (1881-1953). From Richardson's Collected Works (Copyright Bassano and Vandyk Studios).
Figure 3. Jule Charney (1917-1981). From the cover of EOS, Vol. 57, August, 1976 (Copyright Nora Rosenbaum).
Figure 4. Skill of the 36 hour 500 hPa forecast produced at NCEP. Forecast skill is expressed as a percentage of an essentially perfect forecast score, for the period 1955-1999. The accuracy of prediction is closely linked to the available computer power; the introduction of new machines is indicated in the figure. Thanks to Bruce Webster of NCEP for the graphic of S1 scores.
Figure 5. The anomaly correlation (AC) for the 500 hPa height forecast for the Northern Hemisphere, as a function of forecast length. The three curves are for different winters: Black, 1972; Green, 1980; Red, 1998. Thanks to David Burridge, Director of ECMWF, for the graphic.
Figure 6. An artist's impression of Richardson's Forecast Factory, described in Section 11.2 of his book. Richardson estimated that 64,000 `computers' would be needed to keep pace with the atmosphere. Thanks to the artist, François Schuiten, and to Jean-Pierre Javelle, Météo-France, for providing the image.