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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-291
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
09 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Characterizing severe weather potential in synoptically weakly forced thunderstorm environments
Paul W. Miller and Thomas L. Mote Department of Geography University of Georgia, Athens, Georgia
Abstract. Weakly forced thunderstorms (WFTs), short-lived convection forming in synoptically quiescent regimes, are a contemporary forecasting challenge. The convective environments that support severe WFTs are often similar to those that yield only nonsevere WFTs, and additionally, only a small proportion individual WFTs will ultimately produce severe weather. The purpose of this study is to better characterize the relative severe weather potential in these settings as a function of the convective environment. Thirty near-storm convective parameters for > 200 000 WFTs in the Southeast United States are calculated from a high-resolution numerical forecasting model, the Rapid Refresh (RAP). For each parameter, the relative likelihood of WFT days with at least one severe weather event is assessed along a moving threshold. Parameters (and the values of them) that reliably separate severe-weather-supporting from nonsevere WFT days are highlighted.

Only two convective parameters, vertical totals (VT) and total totals (TT), appreciably differentiate severe-wind-supporting and severe-hail-supporting days from nonsevere WFT days. When VTs exceeded values between 24.6–25.1 °C or TTs between 46.5–47.3 °C, severe-wind days were roughly 5 × more likely. Meanwhile, severe-hail days became roughly 10 × more likely when VTs exceeded 24.4–26.0 °C or TTs exceeded 46.3–49.2 °C. The stronger performance of VT and TT is partly attributed to the more accurate representation of these parameters in the numerical model. Under-reporting of severe weather and model error are posited to exacerbate the forecasting challenge by obscuring the subtle convective environmental differences enhancing storm severity.


Citation: Miller, P. W. and Mote, T. L.: Characterizing severe weather potential in synoptically weakly forced thunderstorm environments, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-291, in review, 2017.
Paul W. Miller and Thomas L. Mote
Paul W. Miller and Thomas L. Mote
Paul W. Miller and Thomas L. Mote

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Short summary
The likelihood of severe weather events in synoptically weakly forced thunderstorm (WFT) environments is best characterized by lapse-rate-based parameters. These measures, also among the most accurate model-derived variables, are posited to best capture the subtle convective environmental differences that favor WFT severity. Forecasters should consider weighting their WFT forecasts in favor of lapse-rate-based parameters over others may be more sensitive to model biases.
The likelihood of severe weather events in synoptically weakly forced thunderstorm (WFT)...
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