I heard that it's twelve dimensional. Used to work with a guy who's PHD thesis was on the diffeq of weather predictions.
Vorticity and divergence are an alternative description of the fluid velocity. They are the curl and div of the fluid velocity, respectively.
Just as the fluid velocity may be discretized in 3 spatial and one time dimension, the fluid's vorticity and divergence may be discretized in three spatial and one time dimension.
QED