In geophysical fluid dynamics, the f-plane approximation is an approximation where the Coriolis parameter, denoted f, is set to a constant value.
This approximation is frequently used for the analysis of highly idealized tropical cyclones.
Using a constant Coriolis parameter prevents the formation of beta gyres which are largely responsible for the North-westward direction of most tropical cyclones.
Rossby waves also depend on variations in f, and do not occur in the f-plane approximation.
In reality, the Coriolis parameter varies in the meridional direction, and so the f-plane approximation is not appropriate when considering flows which span large changes in latitude.