Zonda wind (Spanish:viento zonda) is a regional term for thefoehn wind that often occurs on the eastern slope of theAndes, inArgentina.
The Zonda is a dry wind (often carrying dust) which comes from thepolarmaritime air, warmed by descent from the crest, which is approximately 6,000 m (20,000 ft) abovesea level. It may exceed a velocity of 240 km/h (150 mph).
The Zonda wind is produced by the northeastward movement of polar fronts, and although it is hot and dry at the low-lands, it is the main mechanism forsnow precipitation at the high altitude chains, where it looks asviento blanco, reaching speeds sometimes over 200 km/h. Thus, instead of being a snow-eater, this wind is particularly important for thisarid region, as it is connected to the buildup of the winter snow cover and accumulation over the scarce localglaciers.
While this type of föhn wind may occur over most central parts of western Argentina, its effects are more impressive inLa Rioja,San Juan, and northernMendoza provinces, where the mountain barrier (the Andes) is higher, while to the north thePuna plateau dissipates these winds.
According to studies (conducted over the period 1967–1976), the Zonda wind most commonly starts during the afternoon (between 12 and 6 PM), and tends to last between 1 and 12 hours, though it may present itself intermittently for as long as 2 or 3 days. It is countered usually by the entrance of cold air masses moving northwestward (viento sur). In 90% of the cases, the phenomenon takes place between May and November.
The termzonda also describes a hot, humid north wind in thePampas, in advance of a depression moving eastwards, and preceding thepampero. This wind is also called thesondo.