Mesoscale Convective Systems (MCSs) data registers from June to December during 1990-94 were obtained from the Spanish Nacional Meteorological lnstitute (INM). Sixty seven Mesoscale Convective Systems (MCSs) and fifteen Mesoscale Convective Complexes (MCCs) were identitied through this database. Most of the MCCs and MCSs developed during the last week of Septernber. The dominant synoptic patterns related to the mesoscale systems were cold fronts at the surface with warm and moist low-level cores, and cut-off low or deep trough throughout the middle and upper levels. These synoptic patterns were found in all the cases studied. The hourly centroid location of the MCC was used to trace their tracks, which followed a general direction towards the E or NE in almost ali cases. These trajectories are clearly related to the synoptic patterns found. Finally, a Skew T- Log p thermodinamic diagram from the nearest sounding station to a developing MCC is shown.

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