Review Wave forecasts and small-vessel safety: A review of operational warning parameters Ba ´ rður A. Niclasen a, * , Knud Simonsen a , Anne Karin Magnusson b a University of the Faroe Islands, Faculty of Science and Technology, No ´atu ´n 3, To ´rshavn, Faroe Islands b Norwegian Meteorological Institute Region West, Allegt. 70, 5007 Bergen, Norway article info Article history: Received 26 January 2009 Received in revised form 24 November 2009 Accepted 8 February 2010 Keywords: Wave Forecast Vessel safety Warning parameter abstract Traditionally most meteorological offices forecast height, direction and period of wind sea and swell based on phase-averaged wave models. In recent years, there has been special interest in whether it is possible to produce better forecasts, which include information about high-risk situations that are not resolved by the traditional wave parameters. Here we will review and discuss sea-state parameters and safety warning-indices that have been suggested and investi- gated in recent years. In this review we particularly focus on param- eters that are important for small vessels. Some of the findings are: - A current trend in marine forecasts, going beyond the usual parameters, is tailoring of the product to the end users. The extent to which wave forecasts are tailored to small vessels differs quite a lot among meteorological offices. - Single wave and crest heights are adequately described by first- and second-order theory, respectively. Present understanding of mechanisms behind abnormally high single waves suggests that modulational instability is limited to almost unidirectional seas. - Combining wave height and steepness or calculating the risk of synchronous waves is useful, especially in relation to safety of smaller vessels. - Ship accident statistics suggest that the H m0 value of sea state is not as important as whether this value is unex- pected, due to rapid development or compared to local wave climate. * Corresponding author. E-mail address: bardurn@setur.fo (B.A. Niclasen). Contents lists available at ScienceDirect Marine Structures journal homepage: www.elsevier.com/locate/ marstruc 0951-8339/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.marstruc.2010.02.001 Marine Structures 23 (2010) 1–21