The Levanter is an Easterly wind experienced in the Western Mediterranean. The wind blows from the Alboran Channel and through the Straits of Gibraltar, sometimes with very high winds experienced in the Straits of Gibraltar, extending into the Bay of Cadiz.
The Levanter can occur in three ways, namely;
(1) high pressure over western Europe and low pressure to the southwest of Gibraltar over the Atlantic or to the south over Morocco
(2) high pressure cell over the Balearic Islands (Levante will be localized around the Strait), and
(3) an approaching cold front from the west toward the Strait of Gibraltar. As it usually occurs within stable air under an inversion the Levanter is often, but not always, accompanied by local low clouds, fog, haze and sometimes light rains.
The Levanter often follows a Mistral in the Gulf of Lion and in Gibraltar it is preceded by a slight decrease in air pressure and an increase in air temperature. A late morning to afternoon offshore wind also often precedes a Levanter by one day.
The Levanter can occur at any time of year but is most prevalent between July and October. When it blows, the warm, moist air from the Med through the Straits and high over the rock. The moisture condenses over the rock to form a long white ‘banner cloud’ that is blown, spectacularly, over the rock in a Westerly direction.
The Levanter cloud will only form where wind speeds remain below 20 knots. In such conditions the Rock creates eddies and turbulences, which take the form of sudden violent squalls and gusts, frequently of considerably greater force than the prevailing winds and from almost any direction. If the Levanter exceeds 25 knots, the banner cloud will eventually detach from the Rock and dissolve.
Here is an video example of the Levant cloud forming over The Rock of Gibraltar.