Springtime storms can be exceptionally severe. These atmospheric disturbances may be associated with low pressure, unstable air, southwesterly airflow, and occluded fronts. In addition to severe turbulence, they can spawn both thunderstorms and tornadoes. Although hurricanes are larger and generally cause more property damage, springtime storms can potentially result in a greater loss of life. They may, in fact, produce the most violent weather in the United States.
Individual storms can exhibit considerable variability (Whitaker & Dole, 1995, p. 1178). However, certain factors are thought to promote severe storm formation. Such circumstances may relate to atmospheric pressure, temperature, and wind direction. In addition, meso-scale features can also play a critical role in the development of severe storms (Davis & Rogers, 1992, pp. 329-330).
In general, storms develop from low-pressure systems. Prior to the development of a big storm, a weather map might show several areas of weak low pressure. The transformation of a weak surface low into a severe storm, requires upper-level atmospheric support. Such support usually comes in the form of a more widespread area of low pressure known as a trough (Collins, 1995, pp. 81-84). While a surface low can provide air with a lifting mechanism, the trough enables the full development of convection (Davis & Rogers, 1992, pp. 319-330).
In addition to pressure, temperature is also an important factor in the development of severe storms. The great strength of springtime storms may be caused by temperature contrasts. During the spring, the air moving down over North America from Canada remains fairly cold. However, at the same time, the continent's surface air is beginning to warm: The surface air generally warms earlier in the season than the air aloft (Collins, 1995, pp. 81-84).
Obviously, the occurrence of a layer of cold air over a layer of warm surface air re...