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Category: verification

Hydrometeorological forecast verification: the detail matters!

Hydrometeorological forecast verification: the detail matters!

Contributed by Seonaid Anderson, CEH.  Spending time and effort developing a novel hydrological ensemble prediction system, demonstrating its value, comparing with existing systems, justifying all that effort… there are many reasons why we verify our ensemble prediction systems. Before we dive into the number crunching, a few obvious questions need to be asked. What period to use for evaluation? This is often as long as possible, while maintaining relevance to the current application and subject to the usual computing constraints. What…

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Is One Forecast Model Better Than Another?

Is One Forecast Model Better Than Another?

Blog post contributed by: Tim DelSole* The Sign Test Is one forecast model better than another? A natural approach to answering this question is to run a set of forecasts with each model and then see which set has more skill. This comparison requires a statistical test to ensure that the estimated difference represents a real difference in skill, rather than a random sampling error. Unfortunately, there are three problems with using standard difference tests: they have low statistical power,…

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Lessons from calibrating a global flood forecasting system

Lessons from calibrating a global flood forecasting system

Contributed by Feyera Hirpa, University of Oxford. Hydrological models are key tools for predicting flood disasters several days ahead of their occurrence. However, their usability as a decision support tool depends on their skill in reproducing the observed streamflow. The forecast skill is subject to a cascade of uncertainties originating from errors in the models’ structure, parametrization, initial conditions and meteorological forcing. The Global Flood Awareness System (GloFAS) is an operational flood forecasting system that produces ensemble streamflow forecasts with…

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GloFAS-Seasonal: Global Scale Seasonal River Flow Forecasts

GloFAS-Seasonal: Global Scale Seasonal River Flow Forecasts

Contributed by Rebecca Emerton. My PhD research looks into how we can provide earlier indications of flood hazard at the global scale. One way of doing this is through seasonal forecasts of high (or low) river flow. Seasonal forecasts are designed to provide an early indication that a given variable, in this case river flow, will differ from normal in the coming weeks or months. While many operational centres produce seasonal forecasts of meteorological variables, operational seasonal forecasts of hydrological…

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Skilful seasonal forecasts of streamflow over Europe?

Skilful seasonal forecasts of streamflow over Europe?

Contributed by Louise Arnal, University of Reading & ECMWF Editor’s Note: Don’t miss the brilliant cartoon summary at the bottom of this post! Over recent decades, seasonal streamflow forecasting methods have evolved and diversified, reflecting changes in our scientific understanding of streamflow predictability on seasonal timescales and our increasing computer power. The first operational model-based ensemble seasonal streamflow forecast, called the ESP1,2 (ensemble streamflow prediction), relies on the correct knowledge of the initial hydrological conditions (IHC; i.e. of snowpack, soil…

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