Synoptic evolution of significant tornado days over Nebraska and Iowa from the spring through mid-summer

North American regional reanalysis data (Mesinger et al. 2004 ) were collected for significant tornado days in the months of March through July from 1980 to 2004 for the states of Nebraska and Iowa. Composite analyses were produced to look for variations in patterns associated with significant tornadoes in differing months during the primary convection season. Analysis of the synoptic charts indicates a distinct evolution in both the upper air and surface patterns which produced significant tornadoes across Nebraska and Iowa from early to late spring. The majority of significant tornado days in the early spring months were associated with a dynamic dry line, whereas significant tornadoes in the late spring or early summer were most commonly associated with a stationary or warm frontal boundary. Mean convective environmental composites were then developed for each of the months in the study to show important features associated with the significant tornado days.

Mesinger, F., and Coauthors, 2004: North American regional reanalysis. Preprints, 15th Symp. on Global Change and Climate Variations, Seattle, WA, Amer. Meteor. Soc., CD-ROM, P1.1.