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With the arrival of summer and the holiday season, interest in weather forecasts increases, not only for the weather at the destination but also for conditions during the journey there.
Meteorology has developed continuously and rapidly since the mid-19th century, when the science was organised around national meteorological services and the WMO, the World Meteorological Organization. This organisation, together with a worldwide communications network and the arrival of computers, has ultimately led to increasingly accurate forecasts.
Whereas in 1950 weather forecasts did not extend beyond 36 hours, today forecasts are produced up to 15 days ahead. Transport operators have been able to improve passenger safety and comfort thanks to weather forecasting. The impact of technology on maritime navigation has also been remarkable. On crossings between mainland Spain and the Balearic Islands or across the Strait, captains continuously receive updated maps of forecast wind and wave height. These predictions have evolved significantly over the years, in many cases alongside successive military conflicts.
In this respect, the Second World War was no exception and prompted some of the first attempts to forecast wave conditions during Allied landings using random and mathematical functions. From the 1980s onwards, more complex models known as neural models began to be used, providing more reliable forecasts of expected waves, their period (the distance between waves) and swell (waves generated at a distance that then reach a particular area). These maps have improved dramatically over the past 15 years and have become indispensable for protecting passenger safety and comfort.
Ship crews always consult them and, based on these forecasts and data received from other vessels on the route, make the appropriate decisions, choosing the safest and most comfortable course for passengers or, in exceptional cases, cancelling vessels that are less comfortable in heavy seas, such as fast ferries. Despite advances in forecasting, caution and experience remain essential at sea.
Different terms are used depending on wave height, ranging from calm sea (less than 0.1 metres) to very high sea (6 to 9 metres), with rippled, smooth, slight, moderate, rough, very rough and high conditions in between. Waves do not normally exceed 9 metres. Sea state or wave height should not be confused with so-called rissagues. This phenomenon, involving variations in sea level, has long been known and particularly affects the port of Ciutadella on the island of Menorca. There are still unanswered questions about it, but in simple terms it consists of sudden rises in sea level following a more or less regular pattern. Today, the Territorial Meteorological Centre for the Balearic Islands of Aemet takes them very much into account in its forecasts.
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