“…E-mail: gochis@rap.ucar.edu † The National Center for Atmospheric Research is sponsored by the National Science Foundation climate (cf Tang and Reiter, 1984;Adams and Comrie, 1997;Barlow et al, 1998;Higgins et al, 2003) and readers should refer to these for a more general discussion.] The region encompassing the Sierra Madre Occidental throughout western México has emerged as a locus of convective activity for the NAM (cf Mosino and Garcia, 1974;Douglas et al, 1993;Reyes et al, 1994;Comrie and Glenn, 1998;Hu andFeng 2002, Gutzler, 2004;. Here, frequent convective precipitation, though exhibiting marked interannual variability, is a dominant driver of the annual hydrologic cycle (Gochis et al, 2006a).…”