Results of Detailed Synoptic Studies of Squall Lines

A system of synoptic analysis on a mesometeorological scale has been developed through the combined use of space and time sections applied to all regular and special stations in an area 500 by 900 mi. in the Central United States. Two periods of development of large thunderstorm areas are analyzed. In both of these periods tornadoes occurred. The synoptic model of a squall line in this scale involves three principal features of the pressure field—the pressure surge, the thunderstorm high and the wake depression. Another feature, called the tornado cyclone, accompanies tornado funnels. Divergence values of 10 to 60 · 10⁻⁵ sec ⁻¹ over areas of 100 to 10,000 sq. mi. are measured. The mesosynoptic disturbances greatly influence the situation as viewed on the regular synoptic scale, which is about 10 times the meso-scale, and make conventional analysis hopelessly difficult.