Comparisons of Tropical Cyclone Simulations with and without the Assumption of Circular Symmetry

Results from a three-layer asymmetric hurricane model previously described by the authors are compared with results from an axially symmetric analog to investigate the effect of the symmetry assumption on the internal dynarnics of model cyclones. The symmetric model storm initially develops more rapidly then the asymmetric storm. The differences in intensity during the first 100 hr are related to differences in horizontal resolution produced by the staggered grid used with the symmetric model. The symmetric model, on the other hand, does not produce the second period of intensification that starts at 120 hr in the asymmetric model. This fact supports the conclusion reached in the earlier paper that the development of large-scale asymmetries at 100 hr is closely related to the subsequent intensification. Although the life cycles of the two storms are different, the azimuthally averaged structure of the asymmetric storm at maximum intensity is similar to the correEponding structure of the symmetric model storm and supports the adequacy of symmetric models in investigating many aspects of tropical cyclone structure.