Studies have shown how signal delay in Global Positioning System (GPS) estimates of refractivity in the atmosphere can be valuable in augmenting current moisture data collection techniques. A number of existing GPS networks worldwide measure integrated precipitable water (IPW) based on signal delay from the satellites to the ground receiver along with surface temperature and pressure at the site. This study will compare values of GPS-derived IPW with model output from the Air Force Weather Agency’s (AFWA) MM5 in areas with existing GPS meteorological networks, such as those in England, Japan, Germany, Oklahoma, and Florida. An attempt will be made to determine whether MM5 results correlate well with the sensor networks. This research is still in the preliminary stages. Initial results will be presented along with the planned direction for future study.