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1 , I NTRODUCT ION Thermodynamic analyses of vertical profiles of temperature and moisture are requi red to understand the underlying controls of convective cloud development and precipitation at HIPLEX (High Plains Cooperative Program) sites. To obtain these observations. special rawinsondes were launched at HIPLEX field sites during the field season from May to July 1979, HIPLEX is a program designed to develop scientifically proven and socially and economically acceptable techniques to modify convective rainfal I through cloud seeding [4], This report provides a comprehensive summary of thermodynamic structure observed at each HIPLEX site during the 1979 field season, Vertical profiles of temperature. dewpoint. and wind velocity are plotted on thermodynamic diagrams - the skew T-log P diagram [5] for all HIPLEX soundings archived in the Service's (Water and Power Resources Service) Environmental Data Network. 2, RAWINSONDE SYSTEMS Soundings were collected at the Miles City. Montana (ML) field site from May 1 to July 31.1979, Miles City is located in southeast Montana (fig. 1). Early morning (1200 G,m.t.) and midafternoon (2000 G,m.t.) soundings were routinely collected on each operational day at the Miles City municipal airport by Hartzell [1]. These soundings were observed using an RD-65A. automatic tracking system. Six-hundred-gram balloons were used with standard NWS (National Weather Service) sounding instruments complete with parachute and battery (at night), Normal ascent rates required 2 hours to reach the 100-mbar pressure level. at which time the data collection and data reduction were terminated. At Big Spring. Texas (BG). the TEXAS HIPLEX program launched rawinsondes from seven sites located in a meso-network shown in figure 1, These sites launched a series of 3 hourly observations beginning at 1500 G,m,t. and continuing through 0300 G,m,t, on 20 mesoscale days between May 20 and July 19. 1979. Mesoscale days were declared when deep. moist convection in the form of lines or clusters was e x pee t e din the vie i nit y 0 f the me son e t [ 2] '/_ The same standard NWS rawinsondes and balloons were used at the Texas HIPLEX site as in Montana; however. in Texas an RD-65A system was used at Big Spring and five GMD-A systems were provided by the NASA (National Aeronautics and Space Administration) Marshall Space Fl ight Cel')ter to complete the mesonet. The NWS Midland. Texas WSFO provided special soundings from the southwest corner of the mesonet. The exact sounding site shown in table soundings on purposes, latitude. longitude. and elevation of each HIPLEX and the number of soundings observed at that site are 1, Note that Big Spring. Texas routinely took two each HIPLEX operating day for analysis and forecast