The National Oceanography Centre Liverpool develops and maintains tide-surge models used for forecasting storm surges on the coasts of England and Wales for the Environment Agency.
Schematic diagram of the surge forecast and flood warning system
Tide-surge models are run in real-time as part of the forecast suite of models at the Met Office. Results are transmitted to the Environment Agency and used, together with data from the National Tide Gauge Network, for coastal flood warning in England and Wales.
The first operational surge forecasts were run in 1978 using coarse grid surge and atmospheric models. The present system comprises a 12km shelf model (CS3X), with refinements to 1km and a 1-D river model to provide useful predictions in the complex regime of the Bristol Channel and Severn Estuary.
The models are forced by met data from the Met Office's 12km grid North Atlantic European (NAE) weather forecast model.
Comparison between observed and predicted (6-18hrs in advance) surges at Sheerness
Surge models run four times per day producing forecasts up to 2 days ahead. The model surge is combined with tides predicted at tide gauge sites to give the best estimate of the total water level. The Bristol Channel models have also been tuned to provide accurate water level forecasts, eliminating some problems in combining tide and surge in this highly non-linear area.
Predicted distribution of surge (m) at 2200 GMT 4/2/1999 from the CS3 model
Model performance is routinely monitored at the National Oceanography Centre Liverpool by comparing forecast results with observations every month. Typical root-mean-square errors are about 10cm. Significant forecast errors are investigated and causes diagnosed so that the system can be progressively improved.
Future developments under review include: