Analysis of the insurance impacts of storm clusters: a case study with Generali France

Clusters of storms are defined as sequences of multiple storms occurring within a short time frame and a limited spatial extent. In this study, storm clusters are identified using a Lagrangian approach combined with an absolute frequency metric within a 96-hour time window, reflecting reinsurance contract specifications for an insurance company. Compound storms are further constrained to affect a common area, determined by the intersection of their footprints. Those footprints can be delineated using various radii of different sizes, depending on the desired granularity for compounding analysis.

The motivation for this definition stems from the potentially severe impacts of such events on the insurance sector. Storms are known to be among the costliest events for Insurance in Europe, with an average annual insured loss of €217 billion [Copernicus, 2023]. The repetition of such intense wind and strong precipitation events is no exception. The successive storms Lothar and Martin in December 1999 remain the costliest events observed in France with an estimated loss of €17 billion [EEA, 2023]. Despite the substantial risks associated with these compound events, few studies have investigated their role in amplifying both the hazard and the vulnerability.

We apply this approach to Generali, an Italian insurance company with approximately 5% market share in France. Using Generali’s historical claims data from 1998 to 2024, we propose a novel methodology linking high-resolution claims to individual storm events. This approach represents a significant advance in understanding loss drivers. Applied to storm clusters, the methodology distinguishes the relative contribution of each storm in a cluster to the total observed loss. By comparing the findings with Generali’s portfolio from 2018 to 2024, we identify key factors contributing to the additional damages caused by storm clusters. These insights are crucial for enhancing risk prevention and adapting current insurance strategies to better address compound storm events.