A Study of Thunderstorm Formation Along Dry Lines

Abstract

A study designed to point out the effect of the frequently sharp CT-MT boundary, herein called the ?dry line,? on thunderstorm development was undertaken using synoptic surface charts, upper air soundings, 500-mb charts, 700-mb charts, and hourly radar summaries for the spring months of April-June from 1959 through 1962. Plots of new radar echo area formation versus distance from the surface dry line were made for all days on which the dry line was discernible, and it was found that the immediate vicinity of the dry line is indeed a highly preferred thunderstorm developmental zone. Activity also was found to develop carrier and organize more frequently into line formation along the dry line than at locations further removed. 500-mb supporting features were found present in a majority of cases. When equal amounts of moist and dry air were mixed, thunderstorm formation appeared feasible in all cases, even without the aid of convergence between moist and dry air. Essentially the same was true, however, for the unmixed moist air in the first 50 mi east of the dry line.