Orographic vortex

From Glossary of Meteorology



orographic vortex

Atmospheric vortex or whirlwind produced by flow over or past mountains and other obstacles.

Orographic vortices exist over a wide range of scales and orientations, from eddies of a few tens to a few hundreds of meters across, oriented in any direction, and shed by individual peaks or other topographic obstacles, to synoptic-scale cyclones, vertical vortices that form or intensify in the lee trough downwind of mountain-range scale barriers (
see lee cyclogenesis). Eddies of several hundred meters to a few tens of kilometers across (the larger scale representing approximately the scale of the mountain producing them) contribute to aircraft turbulence and enhance damage during downslope windstorm conditions. They often are the result of periodic shedding from the obstacle that produced them. Especially strong vertical vortices have been called "mountainadoes," indicating a resemblance to mountain tornadoes. Under strong convective heating conditions vortices spawned in the mountains sometimes continue downwind over the heated plains and participate in the initiation of dust devils.


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