I have a question about the dynamics of westward propagating vortices. In meteorology, the vorticity tendency is often used to explain the westward propagation of vortices (cyclonic circulation).
A good paper that utilizes this is as follows: https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-14-00170.1
"Development and Formation Mechanism of the Southeast Asian Winter Heavy Rainfall Events around the South China Sea. Part I: Formation and Propagation of Cold Surge Vortex" by Chen et al. (2015).
This paper used the vorticity tendecy equation at 925hPa.However, I am wondering if it is correct to apply this at this level. Should this be more appropriate at 850hPa or higher levels, where terrain effects are minimal especially over the maritime continent?