Mixed type I-II ELMy H-mode, a mode operation with small frequent type II ELMs interrupted by occasional large type I ELMs, has been observed in various experimental situations. Starting from MHD stability analysis of predictive transport simulations constituting a scan in the level of external neutral gas puffing, this paper presents a model for mixed type I-II ELMy H-mode as well as for pure type I, type II and type III ELMy H-mode. The 1.5 D core transport code JETTO has been equipped with an implementation of the model. Some justification from theory and numerical analysis is given for the best representation of type II ELMs. It is demonstrated through predictive transport simulations with JETTO that the model can reproduce the experimental dynamics of mixed type I-II ELMy H-mode. A simulation of mixed type I-II ELMy H-mode is compared with reference simulations of pure type I, type II and type III ELMy H-mode in terms of ELM characteristics and confinement and the differences are explained. Apart from in discharges with strong gas puffing, a topic discussed at the beginning of the paper, type II ELMs have also been experimentally observed mainly in discharges with a quasi double null magnetic configuration, in discharges with high poloidal bp (ratio of the total pressure to the kinetic pressure) and in discharges with a combination of high edge safety factor q95 and high triangularity d. By means of MHD stability analysis performed on interpretative or predictive JETTO simulations, each of these situations is shown to be favourable for type II ELMs according to the ELM model used in the paper.