Wind of southerly wind

The wind of southerly wind is a Vent the blowing in south/south-western of the France, coming from south-east/south-south-east, which affects the Roussillon, the interior of the Languedoc and the Toulouse South. One says of him, in the areas where it prevails - i.e. mainly the Languedoc-Roussillon and the the Midday-Pyrenees - which it can make insane!

Characteristics

It blows until Toulouse and even sometimes Montauban or Agen, like on the plates of the south of the Périgord and on the average valley of the the Dordogne. Its zone of influence covers 35.000 km ². It is most frequently about a dry and hot wind often characterized by a certain turbulence due to accelerations which he undergoes while engulfing himself in certain valleys (prolongation of the Marin wind) as between Carcassonne and Mazamet. Its mean velocity lies between 30 and 40 km/h but it can reach 100 km/h or more in gusts (144 km/h measured in Toulouse on April 14th 2003).

It was formerly the wind of the windmills in the south of the Périgord and in the Top Agenais.

The wind of southerly wind is formed under the action of two phenomena. The first is the appearance of a depression along the Pyrenean barrier because the wind of the south being blocked against the the Pyrenees causes a zone of low pressures, supporting the air flow coming from the Mediterranean by the corridor of the Lauragais between Corbières and Black Montagne. The second phenomenon is what one calls the Effet of Foehn which is formed along the Pyrenees. It reinforces the first depression because the cold air in the north of the Pyrenees is attracted by the hot air located at the south of the mountainous chain. Lastly, this effect Foehn also finds on the northern slope of the Black Montagne, increasing the speed of the wind with Revel and Saint-Felix-Lauragais.

The wind of southerly wind is then wedged between the Pyrenees and the Black Mountain what accelerates the air coming from the Mediterranean (the Marin wind) by effect Venturi. This phenomenon is reinforced by the effect Foehn which causes a layer of fresh air falling down and blocking in low altitudes the wind of southerly wind. In the passing of the Threshold of Naurouze, the point more tightened, the wind undergoes a depression starting of many violent turbulences with swirls and irregularities in speed.

Distinction

One distinguishes several forms from them:

First of all the most usual known as white southerly wind of which the duration of breath can go up to one week; it is a dry wind and generally associated with the good weather; expenses in winter, heat in summer, it comes from association between a anticyclonic situation on the Europe of the Baltique and a depressionary face located on the Portugal.
the other form, less frequent, is the black southerly wind , which operates in the prolongation of a marine wind whose rate of moisture is enough high to preserve a share of this one after having crossed the involved reliefs: it is a hot wind which can bring precipitations. Its duration of breath generally does not exceed the two days; it is related to a depressionary mode located in the the Bay of Biscay and moving towards the North-East.
the southerly wind of Siberia is another form coming from North East, very cold and very violent one who prevails only in February.

Anecdotes

The wind of southerly wind is responsible for the swing of the Toulouse-Revel train on May 4th 1916.

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