Convection-permitting models for managing hydrological extremes: practical, innovative examples.

There is widespread evidence to indicate the role convection rainfall plays in hydrological extremes. In this article, the authors suggest that convection-permitting modelling (CPM) is important for the management of both flood risk and urban pollution from sewerage systems-each of which can be regarded as a hydrological extreme. CPM can be used both for real-time flood alerting, when used probabilistically (an ensemble prediction system (EPS)) in numerical weather prediction (NWP) mode, and can also be used to produce long-term projections of changes to convective rainfall characteristics in future climates. Examples of its use in both of these time scales are presented, highlighting innovative uses of CPM for developing flash flood guidance in Sierra Leone, West Africa and for developing a rainfall time-series perturbation tool allowing water and sewerage companies in the UK to better plan for future rainfall conditions in sewerage networks. Both examples involved close collaboration with end users, co-designing and co-creating the services to be focused on the user needs. The authors look forward to future developments in these two uses of CPM to manage hydrological extremes.This article is part of the discussion meeting issue 'Hydrology in the 21st century: challenges in science, to policy and practice'.