Landfalling tropical cyclones in the Eastern Pacific. Part II: WRF simulations of John and Paul (2006)

Three tropical cyclones that developed during the 2006 season over the eastern Pacific Ocean, made landfall in northwestern Mexico. John affected Baja California and Lane and Paul brought intense precipitation to the mainland. The observational characteristics of these events are described in a companion study at this conference (Farfan et al) and, here, we focus on numerical simulations that were performed using the Weather Research and Forecasting (WRF) model.

The genesis of John occurred in the Gulf of Tehuantepec and then moved parallel to the Mexican coast to make landfall in the Baja California peninsula. Its slow motion resulted in precipitation that exceeded the maxima observed during the last 30 years in the mountainous regions in the southern peninsula. In contrast, Paul developed in late October when low and mid-level winds exhibited a significant westerly component. The storm made landfall in Sinaloa on 26 October and the interaction with the Sierra Madre Occidental also resulted in intense precipitation.

Our WRF simulations were initialized with GFS analyses, included 2 nested grids (30 and 10 km resolution) and were performed for 4 days following the first detection as issued by the National Hurricane Center. The model trajectory for John's circulation is reasonable reproduced for the first 2 days of simulation but it fails to make landfall in the southern tip of Baja California, predicting a more westerly course than observed. Paul's track was more complicated that that of John; nevertheless, the WRF simulations were able to capture its behavior adequately. The accumulated precipitation was compared with the observations of TRMM and GOES estimates. It is clear that these simulations, even at the high resolution utilized, underestimate the amount of the observed precipitation, likely related to the fact that the topography is not well resolved in the model.