## Abstract

If an azimuthally symmetric barotropic eddy on the *f* plane is subject to a relatively small amplitude disturbance of unit azimuthal wavenumber (*m* = 1), it can propagate very many diameters away from its origin, as shown by a weak nonlinear theory for a piecewise uniform vorticity eddy, and also for one with continuous vorticity inside a finite area. In the former case an initial value contour dynamical calculation shows that the analytical solution is realizable over long distances; the same is true in the latter case, as shown by spectral calculations using the full two-dimensional vorticity equation (with small dissipation). The oceanographic significance of this effect lies in the ability of *almost* symmetric eddies to self-propagate over large distances and collide with other eddies, currents, and continents; this produces important mixing effects, as illustrated herein. It is also shown how the analysis and the effect is generalizeable to a 1½-layer density model on the *β* plane.

* Additional affiliation: Geophysical Fluid Dynamics Institute, The Florida State University, Tallahassee, Florida.

*Corresponding author address:* Prof. Melvin E. Stern, Dept. of Oceanography, The Florida State University, Tallahassee, FL 32306- 4320.

Email: stern@ocean.fsu.edu