Maximizing added value in extreme weather forecasting: insights from case studies with the Continuous Global and On-Demand Extremes Digital Twins within the Destination Earth initiative

Destination Earth initiative of the European Commission is creating several digital replicas (digital twins) covering different aspects of the Earth system and based on state-of-the-art simulations and observations. One of the digital twins aims to develop two components of Earth's Digital Twin on Weather-induced Extremes (Extremes DT), with both continuous global high-resolution forecasts, developed by ECMWF and on-demand regional simulations, funded by ECMWF and led by Météo-France.

The Global Continuous Extremes DT is engineered to forecast extreme weather events worldwide with unparalleled precision, providing continuous km-scale global high-resolution forecasts. Currently, the Continuous (Global) Extremes DT uses ECMWF's Integrated Forecasting System (IFS) cycle 48r1 with approximately 4.4 km grid-spacing (TCo2559). On the other side, the On-Demand Extremes (DT) offers configurable digital twin engines for forecasting environmental extremes at a sub-km scale regionally and when necessary. It aims at providing an on-demand workflow with co-design of very high-resolution predictions about extreme weather events combined with decision making support for impact sectors. This On-Demand Extremes DT aims to run a hectometric scale forecasting models with a typical resolution of 750 or 500 m, exploring a finer resolution of up to 200 m for special applications where it is meaningful. In the first phase, capability demonstration aims to explore the added values with co-designing workflow combining the continuous and the on-demand Extremes DT, event- or user-driven solutions with weather forecasting on the one hand, and impact sectors on the other hand. As part as this activity is the focus by examining a range of carefully selected high-impact weather events in both Extremes DT to understand the synergies and the added values that each one provides inside of the Extremes DT.

In this presentation, we will showcase a range of extreme weather events where we demonstrate the predictability capacity of both, the Continuous and the On-Demand extremes DT, and the added value of progressive increment of model horizontal resolution. These cases will be focus on European severe weather, like Mediterranean and Atlantic cyclones and the extreme values in surface variables like wind gusts or precipitation, especially convective precipitation, which is generally better represented at sub-grid km-scale. These selected cases will also provide some insights of how useful is to use the Continuous global Extremes DT to initialise the On-Demand DT compared to the current 9km deterministic IFS.