Introduction to the HyMeX Special Issue on Advances in understanding and forecasting of heavy precipitation in the Mediterranean through the HyMeX SOP1 field campaign.

The Hydrological Cycle in Mediterranean Experiment (HyMeX) is a 10-year international programme devoted to improving ourunderstanding of the hydrological cycle in the Mediterranean area, with special emphasis on the predictability and evolution ofhigh-impact weather events (Drobinskiet al., 2014). Heavy precipitation is a major natural hazard in the Mediterranean. Daily surfacerainfall greater than 100 mm is not uncommon for Mediterranean precipitation events, and often such amounts are recorded inonly a few hours, associated with mesoscale convective systems (MCSs). The occurrence of these heavy precipitation amounts oversmall river catchments that are characteristic of the Mediterranean region often leads to devastating flash floods and flooding events.Each year, these heavy precipitation events (HPEs) result in up to hundreds of millions of euros in damages and many casualties.The distinctive topography and geographical location of the Mediterranean basin (Figure 1) make the region particularly prone toHPEs. Most of these events occur in autumn over the western Mediterranean when sea water is warmest and serves as an importantheat and moisture source from which convective and baroclinic atmospheric systems can derive their energy. The steep orographysurrounding the Mediterranean Sea aids in lifting the low-level, conditionally unstable air, thus initiating condensation and convectionprocesses