A model is proposed as one means whereby an air mass characterized by the "typical" tornado sounding is converted to one described by the type of sounding observed in the vicinity of a tornado. By considering certain indications of the vorticity equation, it is possible to analyze configurations of jet axes and jet maxima such that low-level (850 mb.) convergence is surmounted by higher-level (500 mb.) divergence. Thus a model of jet structures is described which assists in, or possibly in some cases effects, the release of convective instability through vertical stretching or lifting. An example is presented to illustrate the use of this model in tornado forecasting and methods of application are outlined.

Soundings near the time and site of tornado occurrences are examined to determine the air-mass structure ahead of or near the tornado. From the cases studied here, it is concluded that (a) the “typical” inversion was lifted with time such that it was completely absent at the time and site of the tornado and (b), at the same time, the low-level moisture was lifted to great heights. Examples of the conversion of the precedent sounding to the proximity sounding and of a post-tornado case are shown. Composite charts of the moist layer depth and of the Showalter Stability Index prior to and near the time of tornado occurrences are presented.

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Some general characteristics of thirteen tornadoes that occurred on the afternoon of 27 June 1955 in Scottsbluff County, Nebraska, are related. Two of these caused widespread attention due to their size and their proximity to the cities of Scottsbluff and Mitchell, Nebraska. These two were photographed extensively by residents near their paths. The experience of two men directly beneath one of the two large tornadoes is related.