An improved model is presented which simulates temporal behavior in the CO + O-2 reaction on the Pt{100} surface. The model is based on an experimentally determined strongly nonlinear power law for (1 x 1)-CO island, growth rate from the hexagonal (hex) phase with an apparent reaction order of about 4 in the local CO coverage on the hex phase. The power law describes the phase transition from the hexagonal phase of the reconstructed Pt surface to the (1 x 1) phase. Rate parameters from recent adsorption and desorption experiments are used in the modeling. The variations of all adsorbate coverages, the reaction rates, and the surface phase are monitored to provide extensive information about the reaction. New insight into the mechanisms driving the experimentally observed oscillations is gained, and an interpretation of the actual dynamics of the underlying surface processes is also given.