Gibraltar and the Levanter

Whether you love or hate the Levanter, and on asking it appears that most Gibraltarians loathe it; it is here to stay and one can’t help but admire its ever-changing form as many visitors to the Rock will no doubt have captured on camera. So how does it form?

The Levanter is an Easterly wind, its name coming from the Spanish word “levantar” to rise, as in the sun rising in the East. It can be a dry wind if it originates from the Southeast, but more often than not it is a wind from the East or Northeast which, when the air is warm, picks up moisture as it runs over the cooler waters of the Alboran Sea. When winds are light this can give rise to the summer fogs that sometimes plague us, but as winds strengthen this will be lifted and appear as low cloud.

The appearance of the Levanter cloud and how extensive it is depends very much on changes in wind, humidity, how stable the air is and how deep the layer of moisture is. It can appear as a layer of low cloud, or there are the days when it appears as a solitary “Cap” cloud, forming as the wind hits the Rock and is forced upwards allowing the air to cool and then condense to form cloud. This Cap cloud can be sculpted by the Rock itself and with its height constrained by what in meteorology is called an inversion. Under normal atmospheric conditions temperatures cool with increasing altitude, however there are times when this changes, for example as warm air moves over colder air overlying the sea’s surface – this rise in temperature with altitude then acts as a lid on the flow of air/ the depth of the cloud.

The night-time picture of the levanter shows this well, on this occasion, the inversion was just above the top of the Rock, such that most of the wind was forced to flow around its sides, enveloping it in cloud. Meanwhile, the photograph of the more prominent white cap cloud can be seen rising well above the top of the Rock where it is then smoothed off into a lenticular form by a higher level inversion. This type of cloud has often been mistaken for UFO’s at night and one can easily see why.
The deflection of wind by the Rock itself also produces the effect drawn upon in our article on microclimate, when strong winds are seen to fall mysteriously calm at Catalan Bay. If you remember as a child dropping a stone into a fast flowing stream, the water speeds up around the stone and from the flow and ripples of water it is obvious to see that there is an area ahead and in front of the stone where the flow falls light or calm.

There is one significant microclimatic effect which is probably the main downside of the Levanter, especially for those Gibraltarians living in parts of the upper town. Here, under some Levanter conditions, the wind flow can fall calm for days in summer with high humidity, heat and the air stagnating, such that in the 1800’s it was first blamed for the outbreaks of Yellow Fever which blighted the Rock – as written by Jason Musteen in his book, Nelson’s Refuge: Gibraltar in the Age of Napoleon. That was until the discovery was made that it was the mosquito that was the main perpetrator. It was eventually realised that the Levanter may actually have been paramount in helping to contain the disease as the mosquito was seen to be a poor flyer. So for those residents lucky enough to live towards Europa Point or on the East side, in Catalan Bay, these were left largely healthy and unaffected – while the disease was rampant in town.

In more modern times, the summer Levanter can often shroud the west side still with its gloom and unbearable humidity, and while Yellow Fever has long since left Gibraltar’s shores, the Levanter is thought to be a contributing factor in aggravating other ailments such as asthma and arthritis.