FASTEX (Fronts and Atlantic Storm-Track EXperiment) took place during January and February 1997. This experiment allows for the first time to document secondary cyclogenesis at several scales thanks to an important experimental design. Indeed several aircraft carrying dual-beam Doppler radars, microphysical in-situ sensors and launching dropsonde were involved. Combination of these measurements allows to document the mesoscale either in precipitating areas or in clear air region, the synoptic scale environment being described thanks to large scale model analysis.

In the past ten years numerical studies managed to reproduce the life cycle of secondary cyclones involving different processes, such as :

- upper and low level coupling processes.

- low forcing of the large scale environment.

- conditional symmetric instability.

- microphysical processes.

These processes are investigated within secondary cyclones sampled during FASTEX. The IOP16 secondary cyclone, which corresponds to a typical secondary cyclone, involved all these processes and is presently used as reference for comparison with other FASTEX case in order to infer the relative importance of the previously mentioned processes in explosive deepening or non-development.