A reassessment of the UK operational surge forecasting procedure

This report is a summary of the Met Office surge forecasting procedure for the UK, and some investigations into possible sources of error. The forecast is based on the "non-tidal residual", the difference of two model runs with and without weather effects, linearly added to the "astronomical prediction" from local tide gauge harmonics. This method is exposed to several errors. Here we do not attempt to quantify errors in the model or weather forcing, but we show how errors can arise in the harmonic analysis and due to the double counting of weather-related tides. The executive summary, validation guidelines and recommendations have been prepared jointly with the Met Office.