From Glossary of Meteorology
- (Also called circumpolar westerlies, circumpolar whirl, countertrades, middle-latitude westerlies, polar westerlies, subpolar westerlies, subtropical westerlies, temperate westerlies, zonal westerlies, westerly belt, zonal winds.) Specifically, the dominant west-to-east motion of the atmosphere, centered over the middle latitudes of both hemispheres.
At the earth's surface, the westerly belt (or west-wind belt, etc.) extends, on the average, from about 35° to 65° latitude. At upper levels, the westerlies extend farther equatorward and poleward. The equatorward boundary is fairly well defined by the subtropical high pressure belt; the poleward boundary is quite diffuse and variable. Especially in the Northern Hemisphere, even the annual average westerlies are markedly enhanced in some regions, namely, the jet streams.
See polar vortex, antitrades, tropical easterlies, zonal index.
- Generally, any winds with components from the west.