Convener: Nico Becker (Freie Universität Berlin, Germany), Joanne Robbins (Met Office, United Kingdom)

In spite of accurate and timely forecasts, weather related hazards claim many lives and cause significant damages to property and infrastructure each year. This is often due to a lack of understanding of potential impacts of such events, both by civil protection/emergency management authorities and by the population. In 2020 the WMO published the 2nd edition of the Guidelines on Multi-Hazard Impact-Based Forecast and Warning Services to promote best practice in development of effective hydrometeorological warning systems. They stress the need to move from traditional weather forecasts and warnings issued by National Meteorological and Hydrological Services to the provision of multi-hazard impact-based forecast and warning services. To achieve this goal, the whole decision chain from assessing the likelihood of a hazard and its potential impacts to communicating this information to governments, civil contingencies, the responder community and the public needs to be addressed. This requires a strong multi-disciplinary collaboration with partner agencies and significant research into exposure and vulnerability. This session invites presentations related to impact modelling and risk-based warnings with a focus on one or more of the following aspects:

• Acquisition and organization of impact-based information used for model development and verification
• How to track exposure and vulnerability and include those in forecasts and warnings
• How to use ensemble forecasts in impact models and warning systems to assess uncertainties
• Latest research and developments on statistical and physical weather impact models
• Operational impact-based warnings systems
• How to use impact forecasts to aid the decision making process of meteorologists and other hazard specialists in issuing warnings
• Communication and use of impact information by governments, civil contingencies, the responder community and the public
• How impact information helps to aid the decision making process