A significant wave height of 8.44 metres (almost 30ft) was measured by a wave-buoy off Valencia, Spain, at 07:00 on January 20. This is the biggest wave height ever recorded in the Western Mediterranean. Don’t forget that the significant wave height is a kind of statistical summary, which means that there could have been individual waves quite a bit bigger than this, possibly over 13 metres.
The unusually big wave heights were generated by ‘Storm Gloria’ – basically an area of gale-force northeast winds off the coast of eastern Spain associated with a low pressure which deepened off northern Algeria. The storm caused chaos in Murcia, Valencia, Barcelona and the Balearic Islands, with heavy rain and snow, and more than 200,000 people left without power.
Check the Med swell charts to know when to surf, HERE
The evolution of the storm can be traced back to a situation in the North Atlantic that occurred over the previous three to four days. A large meander in the upper airstream in the eastern North Atlantic and a powerful surface high over Ireland developed around 18th January. A small low pressure system west of Ireland was pushed south of this anticyclone and ended up tracking down into Biscay, across Iberia and into the Mediterranean. Late on 19th the low was off Algeria and the pressure gradient on its northern flank increased dramatically as it pushed up against the southern flank of that high; and this is what generated those winds.
Waves don’t usually get anywhere near this big in the Mediterranean, simply because the sea isn’t big enough to hold really big low pressures like you find in the open oceans. Consequently, when you do get anomalies like this, all hell breaks loose along the coastline. Human structures built a few metres from the shore are inundated, with the water overtopping or destroying any breakwaters intended to protect them.
Also, the beaches themselves don’t tend to have any natural sandbars large enough to protect them against such infrequent events. Beaches that get large wave heights on a regular basis, such as those in Southwest France, have a kind of ‘coastal intelligence’ where, under normal circumstances, coastal erosion is naturally limited. The currents produced by the winter storms move the sandbars further out, which dissipate the energy, leaving less energy at the shoreline. In the Mediterranean, wave heights are usually much, much smaller than those on 20th January, so the natural protection was practically non-existent.
Did you know we have an historic search function on the site? Head over to any spot, click the 'FORECAST' tab, then 'HISTORIC' and you can see all the data from any date range you choose. It's a handy tool to compare swells and sessions.