Wave forecasts for the Baltic Sea using ECMWF wind fields as forcing data

Abstract

Wave forecasts for the Baltic Sea area are made at the Finnish Institute of Marine Research (FIMR) four times a day using wind fields from Finnish Meteorological Institutepsilas (FMI) HIRLAM model as forcing data. The forecast length at present is 54 hours but in order to better serve the shipping and safety at the seas the forecast length will be extended to 72 hours within the year 2008. Since the FMI-HIRLAM forecasts only extend to 54 hours the forcing data for the remaining 18 hours or alternatively for the whole forecast length has to be taken from another atmospheric model. For this purpose the wind fields from European Center of Medium Range Weather Forecasts (ECMWF) atmospheric model have been tested for year 2007. The comparison of the wave forecasts runs with forcing wind fields from FMI and ECMWF atmospheric models shows that in open sea areas like the northern Baltic proper the differences between the forecasts are quite small. However, the wave forecasts run with FMI wind fields are better especially close to the coastlines, since with higher resolution (9 km) narrow gulfs and complex structure of the shoreline can be better described than with ECMWFpsilas ~25 km resolution.