This study analyzes integrated precipitable water (IPW) over Arizona southern during the months of July and August. The results show total column (up to 300 hPa) atmospheric moisture, despite illustrating success in predicting precipitation occurrence and spatial extent, does not predict precipitation occurrence, spatial extent, or amount significantly better than do simple low-level dewpoints. Yuma appears to be the exception, as IPW is much more successful in forecasting nearby precipitation occurrence and spatial extent than is low-level dewpoints.
CAPE (convective available potential energy) values are also calculated and compared to precipitation across the region. The results show that CAPE, much like IPW, shows some success predicting precipitation occurrence during the monsoon in Arizona, although it is still less than IPW. Similar to IPW, CAPE is a poor predictor of precipitation totals.