Description of freak waves is not only important for design work but also for operational purposes it would be of benefit if warnings could be given to mariners. Meteo-centers already provide wave forecast based on spectral wave model. Although a spectrum gives some average description of the sea-state, it might contain additional information indicating an increased probability of occurrence of exceptional waves. To this end a database with 650 ship accidents was extracted from Lloyd's Marine Information Service database. Their study may help in identifying the ocean areas more prone to bad weather in general and abnormal waves in particular.
Air travel may be the fastest growing transport mode. However ships are two orders more efficient than air freight (in terms of cost per tonne mile) and hence continue to carry around 95% of the international freight (Faulkner, 2002). Owing to the increasing demands from developing countries, it is also expected that shipping freight may double in the next years and even more attention needs to be given to safety at sea. It is therefore necessary that warning can be given to avoid these cargos to encounter dangerous seas. Although the forecasts are accurate, abnormal sea phenomena may appear suddenly. On September 28th 2000 the passenger ship "Oriana" was hit by a 17-meters wave (Howard, 2000). As reported by the Captain, the ship was handling the weather very well before an abnormal wave struck it. The incident ended without losses, but quite frequently the economic, human and environmental consequences are enormous. Although several can be the causes of ship accidents, approximately 80% of shipping casualties are due to human errors in all phases of the process, i.e. design, constructions and operation (e.g. Gaarder et al, 1997).