For anyone who has ever sailed they will be well aware of the challenges that the weather can set before them, but the Strait of Gibraltar is one of those water courses which can present even the avid sailor with some hidden surprises. The Strait of Gibraltar is an enigma all on its own, with its flow of winds having long challenged sailors since the early days of the Phoenicians in their quest to explore the New World – with many a ship having fallen foul of its turbulent winds and stormy seas. But… this is not the only weather from which sailors can fall foul, there are also the times of becalmed winds, the summer fogs and, of course, the strong tidal currents which often affect these waters.
It is the position of the Strait of Gibraltar as the gateway between the Atlantic Ocean and the Mediterranean Sea plus the mountains which watch over it to the north and south which dictate the predominantly west and easterly winds which flow through it. However, it is the changes in pressure which depict the strength of flow; where winds of just light or moderate strength in the eastern Strait can quickly be transformed into gales as the wind funnels westwards through its narrowest point and into the Bay of Cadiz. By way of contrast, when winds blow from the west some funnelling still takes place although not to the same extent due to the orientation of the Strait. During the winter, approaching storms from the Bay of Cadiz sometimes bring a battle between the Levante and the approaching Vendaval winds which can give rise to some very stormy and dangerous conditions. It is important, therefore, if ever considering sailing the Strait that one learns about its weather and what conditions to expect.
In summer, light winds can in turn cause their own headache and, when combined with the stronger tidal flows also present at this time of year, may easily cause a sailor to find himself sailing backwards! The Strait of Gibraltar acts as a transfer of water between the Mediterranean and the Atlantic taking place in the form of two significant currents, an upper flow of relatively fresh, low-salinity water from the Atlantic eastwards, whereas a lower, colder, denser, more saline flow trickles westwards back into the Atlantic. The rate of these tidal flows are significant and should be borne in mind by every sailor, especially in summer when evaporation is at its highest, enhancing the situation. It may not be known to the reader, but in the ancient times of the long ships it is written that they were able to withdraw their oars and be carried through the Strait on the current; while in the Second World War, German U-boats would also take advantage of it to pass through the Strait undetected with their engines switched off. So, when sailing through the Strait it is very important to bear in mind not just the prevailing wind but the tidal flow in order to make optimum use of both.
Light summer flows of course also bring the added danger of summer sea fogs which can spring from nowhere across the Alboran as variable winds suddenly tend easterly, although westerly flows can also give rise to some considerable fog banks across the Bay of Cadiz into the western Strait.
Expect the unexpected with the Strait of Gibraltar and hopefully you will never be caught out, it is a place where the weather can change considerably during the passage from one end to the other or from one day to the next.