The objective of Lot 1 is to ensure the continued operational delivery, maintenance, and scientific robustness of the Operational Windstorm Service and its ERA5-based extra-tropical cyclone (ETC) diagnostics, datasets, applications and notebooks, while extending the service to meet evolving user needs, especially for insurance/catastrophe modelling, by strengthening QA, providing L2 user support and updated training material, and preparing migration to ERA6 through targeted testing and sensitivity assessment. The extension work includes broadening the geographic domain beyond Europe (to at least Northern Hemisphere mid-latitudes, and potentially Southern Hemisphere), adding variables and derived products (e.g., precipitation linkage, return periods), improving downstream-relevant statistics (including UNSEEN/synthetic/analogue/AI generative approaches with benchmarking and documentation), developing storm indicators usable across reanalysis and climate projections (CMIP/CORDEX) without explicit storm tracking, and co-developing user-driven case studies and online demonstrators with clear documentation and dissemination assets in coordination with ECMWF and (where relevant) Lot 2. | The objective of Lot 2 is to ensure the continued operational running, consistency, and scientific integrity of C3S storm-surge / extreme sea-level products (reanalysis-based coastal water-level time series and related diagnostics) by implementing an operational update cycle (at least monthly), robust QA/QC, and maintained CDS catalogue interfaces/documentation, while preparing for ERA6 via early end-to-end testing and a documented migration plan. In parallel, the lot aims to maintain and evolve derived indicators (percentiles/return periods with uncertainty treatment), explore AI-based approaches (e.g., emulators, post-processing, downscaling) without compromising operational continuity, and restructure/extend the climate projections component so storm-surge/sea-level indicators are produced consistently from a broad, Atlas-aligned CMIP ensemble set with transparent model-selection rules, reproducible processing, and coherent uncertainty characterisation, complemented by updated training/example workflows, L2 support, and cross-lot coordination to enable joint windstorm–storm-surge compound hazard products for insurance and risk-modelling users.