1. INTRODUCTION The elevated terrain in the desert southwest of the United States provides an ideal location in which to observe the onset and transition from shallow to deep convection. Thunderstorms associated with the North American Monsoon

The elevated terrain in the desert southwest of the United States provides an ideal location in which to observe the onset and transition from shallow to deep convection. Thunderstorms associated with the North American Monsoon (NAM) occur on a fairly regular diurnal cycle, with shallow convection developing under often clear skies over the highest peaks a few hours after sunrise. The shallow convection builds as a series of successively taller turrets that rise through the remnants of the preceding ones, transitioning into cumulus congestus and eventually cumulonimbus.