An analysis of the landfall of Hurricane Nora (1997)

The changes to the motion and structure of the eastern Pacific Tropical Cyc lone Nora (1997) during landfall are investigated. Nora developed south of the Mexican coast, intensified into a hurricane, and made landfall over nor thwestern Mexico and the southwestern United States. In this study, the aut hors document the evolution of the structure of Nora from a variety of sour ces. Observations derived from satellite imagery show the approach of the h urricane to the Baja California peninsula and the development of a localize d area of mesoscale convection that intensified while moving over the Gulf of California. The propagation of this convective system became the dominan t feature of the landfall and provided heavy precipitation over a region co nfined to western Arizona. Numerical simulations with the Pennsylvania State University-National Cente r for Atmospheric Research Mesoscale Model version 5 are used to examine th e details of the evolution of the observed area of convection over the gulf . Simulations at different spatial resolutions show that the model is able to provide a reasonable prediction of the changes to the track, structure, and intensity of the hurricane at landfall. In addition, the model fields s how that orographic modification of the low-level flow is involved in the d evelopment of a secondary circulation over the gulf. The simulated location and structure of this circulation are consistent with the observations der ived from satellite imagery.