This paper attempts to interpret, from a single point of view, several at first sight independent phenomena brought into focus through the synoptic investigations carried on at the M assachusetts Institute of T echnology during the last few years. Since this interpretation is very largely based on a consideration of the changes in vorticity which must occur in vertical air columns which are displaced from one latitude to another and since such vorticity changes play a fundamental role also in Ek.man's general ocean current theory (1932), the results would appear to be of enough interest to physical oceanographers to warrant their publication in this journal. The particular phenomena brought out in the course of our studies are listed below. * This paper contains a preliminary report on certain phases of an investigation carried on at the M assachusetts Institute of T echnology in cooperation with the U. S. D epartment of Agricul ture, t he objective being t he development of adequate methods for weekly weather forecasts. The synoptic phases of this proj ct, involving the prepara ti on of da ily weather charts fo r the North rn H emisphere, is under the direc tion of Dr. H. C. Willett wi th the cooperation of Messrs. J. H olmboe and J. Namias. The statistical phases are under the direction of fr. L. P age with the cooperation of Mr. R. Allen, both of the Bureau of Agri ul tural Economics.

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This paper contains an aerological analysis of a series of rapid-moving frontal waves associated with a well developed zonal current over central Europe. The gradual destruction of this zonal flow through a retrograde blocking "wave" is described. The relationship between the blocking process and the deepening of series of waves approaching the blocking zone from North America is discussed. The observational data and conclusions from this aerological study are presented for the purpose of rendering some assistance to theoreticians investigating atmospheric wave motions, by providing a few numerical values for certain characteristic parameters of these waves and by calling attention to a factor which appears to play a significant r61e in the deepening of certain types of extra-tropical wave cyclones, viz. the variation with longitude of the basic current pattern.