This is due to the upper level Low which was established over the western Mediterranean and shifted to the southeast. This type of trough is also called "gota fría" in Spain (cold drop). The counter-clockwise flow brings hot air from North Africa over the warm sea water at this time of the year. As a result, cold air at upper level on warm air + water vapor gives strong convection and heavy rain. This phenomenon caused very heavy rainfall on the French Mediterranean coast and Liguria this week.

Temperature at 500hPa level (approx. 5500m)