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This thesis presents a description of the evolution of the second of three mesoscale convective systems that passed over the PRE-ST0RM mesonetwork on 3-4 June 1985 Three NC-^JK CP-3 and CP-4 Doppler radar volume scans along with Wichita (NWS) WSR-57 radar scans were analyzed with surface wind and pressure data to explain the complex precipitation structure from 2100 to 0200 GMT The precipitation pattern contained a convective line, a northeastward extension of convection called the northeast band, stratiform precipitation m the northern half of the system, and smaller precipitation structures in the eastern portion of the system Detailed analysis of this system shows that the intersection of the convective line and the northeast band produced strong upward motion within an area of intense convection that influenced the surface pressure pattern and the internal circulation generated by the mesoscale convective system.

Supercell thunderstorm structure and evolution is examined on several length and time scales using evidence from the 28 May 1980 Tulia Outbreak storm. Conventional meteorological data are combined with storm intercept team observations and photographic data to perform this analysis. New motion picture photogrammetry techniques are described and used for tornado analysis, and errors arising in photogrammetry are determined. It is found that the storm was triggered by a surface dryline, developed in a favorable environment, and intensified in an area of strong surface temperature gradients. After the storm collapsed it showed cyclic variations in intensity which corresponded to stages in cyclic tornado evolution. The photogrammetry results include a number of new findings. The three-dimensional flow structure is revealed and axial asymmetries are documented. In addition, time variations in tornado morphology, translation, and strength are documented.

A microcomputer simulation of mesoscale precipitation patterns over the Texas South Plains was developed to investigate the variations in a Z-R relationship that are due to the imperfect correspondence between radar and raingage rainfall estimates. Synthetic rain cells were specified in a fashion that depicts the linear structure of squall lines, which account for a large percentage of the total Texas South Plains convective rainfall. The results indicate that gage-radar sampling differences inflict large errors on a Z-R relationship, particularly when gradients of precipitation rate are sharp and the temporal variations in cell strength are great. Raingage measurement variations within a radar bin, variations of radar reflectivity for a succession of bins, and the advection of the precipitation pattern were each found to have the potential to cause Z-R variations of over 30 mm/hr. Attempts to suggest observing system adjustments to diminish such variations were not successful. Evaluated gage-radar sampling differences in the vicinity of strong convection were found to have the potential to be the dominant cause of Z-R relationship variations and responsible for at least part of the difficulty associated with fitting a power law relationship to convective rainfall data.