ADGEO Advances in Geosciences ADGEO Adv. Geosci. 1680-7359 Copernicus Publications Göttingen, Germany 10.5194/adgeo-29-77-2011 The use of MOGREPS ensemble rainfall forecasts in operational flood forecasting systems across England and Wales Schellekens J. 1 Weerts A. H. 1 Moore R. J. 2 Pierce C. E. 3 Hildon S. 4 Inland Water Systems, Deltares, Delft, The Netherlands Joint Centre for Hydro-Meteorological Research, Centre for Ecology and Hydrology, Wallingford, UK Joint Centre for Hydro-Meteorological Research, Met Office, Wallingford, UK Flood Risk Science, Environment Agency, Leeds, UK 01 03 2011 29 77 84 Copyright: © 2011 J. Schellekens et al. 2011 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://adgeo.copernicus.org/articles/29/77/2011/adgeo-29-77-2011.html The full text article is available as a PDF file from https://adgeo.copernicus.org/articles/29/77/2011/adgeo-29-77-2011.pdf

Operational flood forecasting systems share a fundamental challenge: forecast uncertainty which needs to be considered when making a flood warning decision. One way of representing this uncertainty is through employing an ensemble approach. This paper presents research funded by the Environment Agency in which ensemble rainfall forecasts are utilised and tested for operational use. The form of ensemble rainfall forecast used is the Met Office short-range product called MOGREPS. It is tested for operational use within the Environment Agency's National Flood Forecasting System (NFFS) for England and Wales. Currently, the NFFS uses deterministic forecasts only. The operational configuration of the NFFS for Thames Region is extended to trial the use of the new ensemble rainfall forecasts in support of probabilistic flood forecasting. Evaluation includes considering issues of model performance, configuration (how to fit the ensemble forecasts within the current configurations), data volumes, run times and options for displaying probabilistic forecasts. Although ensemble rainfall forecasts available from MOGREPS are not extensive enough to fully verify product performance, it is concluded that their use within current Environment Agency regional flood forecasting systems can provide better information to the forecaster than use of the deterministic forecasts alone. Of note are the small number of false alarms of river flow exceedance generated when using MOGREPS as input and that small flow events are also forecasted rather well, notwithstanding the rather coarse resolution of the MOGREPS grid (24 km) compared to the studied catchments. In addition, it is concluded that, with careful configuration in NFFS, MOGREPS can be used in existing systems without a significant increase in system load.

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