The relevance of conditional symmetric instability to the prediction of mesoscale frontal rainbands

This paper examines the theory of Conditional Symmetric Instability (Bennetts and Hoskins 1979) and considers its relevance to meso‐scale frontal rainbands. The theoretical growth rate of the instability is evaluated from synoptic scale data obtained from a numerical forecast model and compared with observations of the horizontal structure of rainfall observed by radar. One case study is presented in detail and a further 44 cases summarized. Rainbands were observed on 80% of the occasions on which they were predicted.