In the free troposphere, the easterlies are geostrophically balanced and develop in association with increasing pressure to the south.
Lea Beusch, Shira Raveh-Rubin, Michael Sprenger, Lukas Papritz 2018, 'Dynamics of a Puelche foehn event in the Andes', Meteorologische Zeitschrifthttp://dx.doi.org/10.1127/metz/2017/0841. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)