1) Variations of cloudiness and precipitation associated with the North American Monsoon System (NAMS) are dominated by diurnal cycle;
2) Clouds and precipitation start from higher elevation in the morning, move toward the coast as they reach the maximum in late afternoon;
3) The phase of the diurnal cycle is relatively stable, while the magnitude presents changes of synoptic and intraseasonal time scales;
4) Maximum of deep convection and precipitation appears 50-100km west to the mountain crests, and,
5) The intensity of the NAMS convection is positively (negatively) correlated with that of the diurnal amplitude of SSTs over the Gulf of Mexico (the Gulf of California).
Further work is underway to examine how the NAMS diurnal cycle and its relationship to SST are simulated by NCEP operational climate forecast models.