S.S.T. flight operations are likely to commence early in 1970 and meteorological briefing for all flight levels must therefore be established, especially for temperature, wind and clear-air turbulence. This paper, which was presented to the S.S.T. Working Group, outlines the accuracy of temperature prediction over 24-hour periods and suggests forecast rules. Finally the resultant requirements are stated.

Several conceptions of possible and desirable temperature forecasting accuracy have been expressed in relation to S.S.T. performance by different panels. For example, the Fausst WP 529 (Franco-Anglo-U.S.-S.S.T. Working Paper 529), revised 3 March 1967, recommends a maximum standard error of 3°C for temperature forecasts at the S.S.T. level, which means the accuracy of temperature forecasting must be within a range of ± 3°C in 68 per cent of all cases. After other recommendations, such as the I.C.A.O. S.S.T. panel, July/August 1968, the subsonic requirements may be adopted for the S.S.T. too; these recommendations allow a standard error of 1°·8C, i.e. the accuracy of temperature forecasts must be within a range of 1°·8C in 68 per cent, or 3°C in 90 per cent, of all cases.