Climatology of Potentially Severe Convective Environments from the North American Regional Reanalysis

Victor A. Gensini,Walker S. Ashley

doi:10.55599/ejssm.v6i8.35

Victor A. Gensini, Walker S. Ashley

Open Access

https://doi.org/10.55599/ejssm.v6i8.35

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Abstract

This study establishes a U. S. climatology of potentially severe convective environments for the 30-y period 1980-2009 from the North American Regional Reanalysis. Variability of environments supporting significant severe weather is examined for four active severe-weather regions in the U. S. Regional comparisons illustrate potentially significant-severe environments varied greatly both spatially and temporally over the 30-y period of record. The spatial and temporal distributions of significant severe-weather environments and reports are subjectively examined for comparison purposes. While one has to be cautious when linking environments and reports, average calculated significant severe-weather environments show similarities to the annual cycle of significant severe-weather reports. Additionally, mean center analysis indicates that there is no significant shift in the average position of these environments during the period of record.

Highlights

Background aDMC environmentsDiagnostic parameters such as CAPE, convective inhibition (CIN), storm-relative helicity (SRH), 0–6-km bulk wind difference (BWD), and lifting condensation level (LCL) are all useful in determining the potential for DMC (Rasmussen and Blanchard 1998; Rasmussen2003; Craven and Brooks 2004)
Results from this study indicate that some of the largest decreases of potentially significant severe-weather environments, after incorporating CIN, were located in this region
S. climatology of significant severe-weather environments for the period 1980–2009 using reanalysis data. This has been accomplished on a global scale for a shorter period, but no prior study has employed new, high-resolution reanalysis datasets, such as the North American Regional Reanalysis (NARR), to analyze convective environments

Summary

Introduction

Background aDMC environmentsDiagnostic parameters such as CAPE, convective inhibition (CIN), storm-relative helicity (SRH), 0–6-km bulk wind difference (BWD), and lifting condensation level (LCL) are all useful in determining the potential for DMC (Rasmussen and Blanchard 1998; Rasmussen2003; Craven and Brooks 2004). The ingredients-based forecasting methodology (Doswell et al 1996) uses parameters analyzed by forecasters in a prognostic sense through extrapolation and numerical weather prediction. Forecasters historically placed thresholds of these parameters on a composite chart (Miller 1972; Crisp 1979) to represent the greatest threat for DMC. Combinations of different ingredients found on composite charts and sounding presentations have been used to develop composite indices. Composite indices often are employed in discriminating between atmospheric environments favorable for certain types of severe-weather events. Doswell and Schultz (2006) emphasize that forecasters must exercise caution when employing indices and parameters. They argue that these indices seek to simplify the nonlinear atmosphere and should not be treated as a simple solution for where DMC will occur. It is vital to understand exactly which variables enter into the calculation of composite indices, and precisely how they are combined, in order to understand their strengths and weaknesses

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