The Autan wind is a wind of the south-east of France. To the west of Carcassonne, on the hills of the Lauragais and Razès it can be particularly strong. It whips up to a fury around hilltop houses in the area. The Autan begins as a warm south-east wind from the Mediterranean Sea, blows up towards the CÚvennes and the Montagne Noire, often heralding heavy rainfall.
The Autan covers an area to Perpignan in the south, Auch to the west, and Cahors to the north.
Some days before it blows, a calmness descends, characterised by crystal clear air. During this period the Pyrenees may be seen from 150 kilometres away. As farmers say when this happens - "the Autan wants to blow".
The noise of this hot dry wind causes insomnia. It is sometimes known as the Vent des Fous (the wind of the mad) as it can blow for up to nine days on end, allegedly driving people as mad as the Mistral wind, and is also known, rather dramatically, as the devil's wind and the wind of death.
Incidentally, the thirteenth century Song of the Crusade against the Cathars describes a gale of Autan on Sunday 1st July 1218, that coincided with the last attack by Crusaders against Toulouse.
The Autan comes in two varieties L'Autan blanc and L'Autan noir.
It is created by ascending air rotating around a zone of high pressure (typically, an anticyclone centred over Eastern Europe), balancing a depression over Iceland. This causes currents of air turning clockwise, starting on the coast of the Gulf of Lyon and moving to the region of Cahors.
The wind clears the sky, dries the ground, and heralds good weather. Gusts regularly reach 80 to 100 km/h.
L'autan noir. The Black Autan is warm, bringing heavy rain of short duration.
It is much less frequent than the L'autan blanc (but seems to be becoming more common).
When a depression is centred on Spain, balancing an anticyclone over the Azores, it creates an air flow moving anticlockwise. This flow progresses along the coast of Spain picking up humidity from the sea. It generally hits the Languedoc between Perpignan and Béziers, tracking towards Carcassonne, Toulouse and Agen where it dissipates.
In the Lauragais this wind, called the "Marin noir" or "Black Sailor", is characterised by heavy black clouds created by evaporation from the Mediterranean Sea. Sometimes rain precipitates over the Corbières protecting areas further west, but if not the rain will be carried further inland before precipitating.