Edge localized modes (ELMs) are observed during H-mode discharges in JET with widely varying amplitudes and repetition rates [1,2,3]. They can be small and very frequent ('grassy') when an H-mode builds up, but as the edge electron temperature increases, they become larger and much less frequent. The larger, 'singular' ELMs, which were discussed in Ref. [3], are similar to the 'type III' ELMs in DIII-D and ASDEX [5]. Prior to these singular ELMs in JET, pressure gradients near the edge plasma are found to be well below the ideal ballooning stability limit, while resistive ballooning modes with medium to large toroidal mode numbers, n 10, are unstable. In the first part of this paper we extend this analysis to the fast events which sometimes terminate high-bp or hot-ion phases in JET discharges, varying from large ELMs to global events in which central m = 1 activity and fast edge losses occur simultaneously. We find that prior to some of these events, edge pressure gradients are much closer to the ideal ballooning limit, and that the relative importance of the pressure gradient and of resistivity for stability of the plasma near the edge varies from case to case. In part two of the paper, we present asymptotic solutions of the ballooning equation obtained from a generalization of the two-scale expansion method of Ref. [6] to flux surfaces with finite aspect ratio. The result makes an efficient computation of the ballooning D' near the JET plasma edge possible, taking into account up-down asymmetry.