Wind and sea forecasts for coastal waters

Marine engineering operations vary from maintenance of sea defences through to the construction of new offshore wind-farms. There is a need to know precisely about wind and sea conditions so that personnel are not exposed to dangerous conditions and so that the expensive engineering facilities, such as cranes and jack-up vessels used for piling, are deployed optimally. This is particularly important during marginal sea conditions and amongst shallow banks and strong currents.

Predicted wave severity field for Lincolnshire Wind-farm sites
Wind/sea forecasts helped schedule piling operations by the jack-up vessel MV Resolution off the Lincolnshire coast (photo courtesy Centrica).

HR Wallingford has combined its skills and modelling capabilities with those of the Met Office to develop a forecasting service that provides site-specific and accurate real-timer predictions of wind and sea conditions. This service has been used by LNG tanker terminals, Network Rail and the Royal Navy. With the construction of the Lynn and Inner Dowsing offshore wind farms off the Lincolnshire coast, the service has been extended to include the UK renewable energy industry.

The new wind farms – to be installed and run by Centrica – should be fully operational by the end of 2008. Their output will meet almost 50% of Lincolnshire’s annual domestic demand. The offshore construction operations – driving of monopiles, cable-laying, and installation of turbine towers, nacelles and blades – are restricted by specific safe operating conditions. The service has provided the construction team with site forecasts of the prevailing winds and waves and has thereby helped to maximise operational efficiency as well as to minimise risks.

Accurate predicting depends on representing the effects of the series of shallow banks to the north and west of the site that provide shelter (particularly at low tide) from the severe wave climate of the North Sea, and the influence of local winds.

The service comprises twice-daily model runs that provide five-day forecasts on a secure website. Warnings are also directly given on any exceedance of predicted conditions over the defined safe operating thresholds. Actual measurements are provided on the web site alongside the forecasts – for ongoing confirmation of accuracy. Feedback from the construction team on the forecasting service has been positive – to date the system has proved its worth through the ongoing safe and efficient construction programme.

For further information please contact Nigel Tozer, Principal Scientist, HR Wallingford, (01491 835381; E-mail n.tozer@hrwallingford.co.uk).