Oceano-meteorological conditions observed during severe storms in the southern Bay of Biscay

Abstract

Severe storms happen every year in the North coast of Spain. If certain weather and oceanic conditions match, they can be quite destructive, both for ships and structures on the sea and buildings, cars, people or city furniture on land. Systems of meteorological and oceanographic observations are fundamental tools for improve the prediction models and help to reduce the impact of storms on ships, coastal structures and people and improve the security at sea and along the coast. On November 2010 a severe storm took place at the southern Bay of Biscay causing important damage. The relevant aspects of this storm will be studied and compared with previous storms in December 2007, March 2008 and January 2009, leaving this last one a record wave of 26.13m measured at the Augusto Gonzalez de Linares (AGL) buoy. On June 2007, the IEO moored the AGL ocean-meteorological Buoy, 22 miles north of Santander over about 2850m depth, at the position 43°50.67'N, 3°46.2'W to complete the ocean information with the ocean-atmosphere interaction. This buoy is integrated seamlessly in the national buoy network, contributing with its data to oceanographic research, operative ocean-meteorological predictions and seasonal climate predictions. This applications will also be shown in this paper. The AGL buoy is equipped with several sensors, meteorological, oceanographic and biologic. Some relevant parameters than can be obtained from these sensors are: air temperature, wind speed and direction, humidity, air pressure, water temperature, wave height and direction, wave periods, current speed and direction in the first 100m of water, salinity, fluorescence and dissolved oxygen concentration. All the data obtained from the buoy is stored internally and some other parameters are transfered hourly to the Santander IEO center via satellite. The data stored in the buoy is recovered and deployed on every buoys maintenance operation, which takes place three times a year. During the storms in 2007, 2008 and 2009 the AGL buoy measured significant wave heights of more than 10m for all of them, translating to maximum wave heights of 15.22m, 19.77m and 26.13m respectively. The storm in 2010 produced smaller significant wave heights than the previous ones, but during almost all the storm period (November 8th, 9th and 10th) this parameter was always above 6 meters. This persistence made it more destructive in economic terms. Sustained strong winds generated also a continuous pattern of high height waves which reached the coast during spring tides and where the mean water level was also at a maximum value, 0.34 meters over the mean of the corresponding month and 0.46 meters over the annual mean, and, finding tidal residuals up to 0.40 meters at high water level. The weather conditions that raised these waves will be studied and compared deeply in this paper. For this purpose, the help of meteorological models is invaluable.