"The primary purpose of this paper is to present a significant scale of meteorological events. This scale, the mesoscale, is either overlooked or intentionally ignored in much of the analysis being done today. The reason normally given for this omission is the fact that these meteorological motions are essentially 'noise' superimposed on larger-scale circulations and it is with these larger-scale circulations that most of the meteorologists' efforts (both theoretical and synoptic) have been concemed. It is our opinion, however, that this 'noise' is directly tied up with the local weather and that the meteorologist will have to despair of ever being able to predict this local weather with a satisfactory degree of confidence unless he has accurnte knowledge of what is going on in the mesometeorological scale of motion. In addition to focussing the readers attention on this scale of motion, it is also the purpose of this paper to serve as a preliminary manual for mesoanalysis. Although most of the analysis techniques have been given elsewhere (T. Fujita, 'Results of Detailed Synoptic Studies of Squall Lines', Tellus, vol. 7, No. 4, 1955, pp. 405-436), they are described fully here for completeness. Moreover, all of the ditta used in the analysis have also been reproduced in the form of station time sections. It is intended that these will serve two purposes: (1) The reader is encouraged to follow the techniques presented, perform his own mesoanalyses and compare them with the results given here, and (2) the reader will be able to interpret the sequence of events as they transpired at any station in terms of the mesosystems, developed in the analysis, which passed the station. Finally, we wish to point out that we have concerned ourselves here with analysis and not with explanation. The analyses clearly show the formation, development, movement, and dissipat ion of mesostruct ures. From this point of view the primary purpose of the paper is realized. However, there still remains the problem of explaining the life history of the mesostrnctures from a dynamical point of view"--Preface