(Also called altanus
.) A strong southeast wind
in south-central France, especially in Gascony and the upper Garonne River.
Near the Pyrenees the autan is very turbulent, growing in strength in the valleys. At Toulouse its average speed is 13 m s-1
(30 mph) with gusts of 20–22 m s-1
(45–50 mph); it tends to be strongest at midday. It increases in speed up to a height of 450 m (1500 ft), above which it weakens and veers to the south. North of Toulouse it loses its special character and becomes an ordinary southeast wind. There are two types. 1) The autan blanc brings fine dry weather, cold in winter, hot in summer, as a result of the downslope motion imposed by the Pyrenees and southern Cevennes. It occurs with an anticyclone
centered near Denmark or moving northeastward from the Azores. It lasts for two to four days in winter, but may persist for more than a week in summer, bringing severe drought
and desiccating the vegetation; in Catalonia (northeastern Spain) a similar wind is called the outo
. 2) The autan noir is less frequent and rarely lasts for more than two days; it is more humid and cloudy
, bringing fog
, or snow
over high ground near the sea. As such, it is more like the marin
, the name applied to the southeast wind out of the Cevennes where its maritime character predominates.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact email@example.com. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.