Precipitable water at Vici, Oklahoma (VICI) for 1200 UTC 6 May to 0000 UTC 10 May 1994. The small blue dots represent radiometer measurements along the line-of-sight to GPS satellites, mapped to the zenith. The red dots represent 30-minute averages of precipitable water (PW) calculated from the least-squares fits of GPS wet delay. Vertical arrows denote the time of the observed surface dry line passages at Vici. Time of thunderstorm activity is indicated with conventional symbols.