SuhfhfARYIn an attempt to obtain a better approximation to the horizontal flow of a non-divergent fluid than the geostrophic approximation, a Monge-Ampere type of partial differential equation, similar to that of Charney (1955), is derived to enable a stream function to be found from the contour height field. A method is given for the numerical aolution of this equation.The stream fmction has been used in place of the contour height parameter to represent the flow at the mean level in computing three 24 hr forecasts based on the Sawyer-Bushby two-parameter model of the atmosphere, and the results are compared with similar computations without the stream function.In one situation, the use of the stream function produced a marked improvement in the Computation.

S W YThis paper describes an objective technique for analysing sets of upper-air data. The analyses resulting from the application of this technique to four sets of data for the NE Atlantic and Europe were compared with those produced subjectively by an analyst, and no marked differences were apparent.Numerical forecasts for twenty-four hours ahead based on both subjective and objective analyses were computed for these four situations and the results compared with the actual developments. Only slight differences were noticed between the forecasts based on the subjective analyses and those based on the objective analyses in three of the four situations, but in the fourth situation the numerical forecast based on the objective analysis was much the better.