The erosion of the vortices in rotating shallow water model is analyzed in order to rationalize observed amplification of fluid rotation inside long-lived geophysical eddies during their evolution. The stripping of typically elliptical vortex core due to an external strain or weak instability is taken into account for vortices with uniform potential vorticity outside the solid body rotating vortex core. Matching the geostrophycally adjusted velocity at the core boundary allows for evaluating the amplification of fluid rotation rate in the vortex core for a given rate of the core shrinking and the model parameters. The amplification in cyclonic vortices is shown to be stronger than in anticyclonic vortices due to preservation of the finite potential vorticity anomaly inside their cores. This mechanism of vortex intensification has important implications for understanding the longevity of geophysical eddies.