Demonstration of the benefit of increased spacial resolution provided by a GPS receiver network. (a) Objective analysis of precipitable water (in mm) using radiosonde derived PW data for 8 May 1993 at 0000 UTC. Small numbers indicate PW values at radiosonde sites (black circles). Purple dashed line in each panel indicates National Meteorological Center analyzed position of dry line. (b) Objective analysis of precipitable water using radiosonde and GPS derived PW data. Small numbers indicate PW values at radiosonde (black dots) and GPS sites (red dots) (adapted from Chiswell et al. 1996). The high PW value of 32 mm at Vici, Oklahoma (VICI) is consistent with thunderstorm activity observed in that area.