Synoptic, meso, and storm-scale conditions associated with strong-to-violent nocturnal tornadoes

Nocturnal tornadoes, although relatively rare when compared to their daytime counterparts, are over 60% deadlier. Not only is the public less situationally aware after dark, but also nighttime tornadoes are most common in regions of the country with a high density of manufactured housing, which is known to be considerably more susceptible to significant tornado damage. In light of this, there has been surprisingly little research into discovering the conditions under which nocturnal tornadogenesis is most likely.

The purpose of this paper is to examine the environmental characteristics under which seven different strong-to-violent nocturnal tornadoes occurred, and from that develop a better understanding of which atmospheric conditions are most supportive of nighttime tornadogenesis. For each storm in the study, the location of first strong-to-violent tornadogenesis in relationship to surface and upper-level synoptic features was determined. In addition, several severe storm forecast parameters for each event were quantified. When inspecting the patterns evident over the spectrum of the storms, particular attention was paid to the evolution of the storm-relative wind speeds, especially near the ground, as well as the stability of the planetary boundary layer.

We believe that the findings of this study will shed light on what particular nighttime conditions are favorable for strong or violent tornadoes, and hence be of great benefit to the quality of short-term forecasting. Future research on this topic will include a more in-depth inspection of the 9 May 2003 storm because of the wealth of unique data available on this storm, as well as a numerical simulation of the 9 May 2003 storm in what was suspected to be a stable planetary boundary layer.