Understanding how these environmental features and their impact on accompanying convection evolve with time are vitally important for determining the ability of storms to produce severe hazards through the EET. These and other related factors have been offered up as explanation for the peak in near-sunset tornado counts noted in the literature (e.g., Kelly et al. 2016), which can introduce additional low-level shear and storm-relative helicity (SRH) into nocturnal storm environments (relative to daytime environments) and have potential ramifications for storm maintenance and tornadogenesis (e.g., Maddox 1993 Markowski et al. These thermodynamic changes are often accompanied by the onset of nocturnal low-level jets (NLLJ Blackadar 1957 Shapiro et al. The hours soon before and after local sunset constitute the early evening transition (EET), a period during which surface radiational cooling results in increasing static stability and convective inhibition (CIN). However, HSLC tornado prediction can be improved by considering variables like precipitable water, downdraft CAPE, and effective inflow base. Existing forecast guidance metrics such as the significant tornado parameter (STP) remain the most skillful predictors of HSHC tornadoes. Furthermore, the existence of HSLC storm environments presunset increases the likelihood of nonsupercellular tornadoes postsunset. These low-CAPE environments sustain higher values of low-level shear and storm-relative helicity (SRH) and destabilize postsunset-potentially compensating for minimal buoyancy. Results indicate that HSLC environments evolve differently than HSHC environments, particularly for nonsupercell (e.g., quasi-linear convective system) modes. Last, statistical analysis is performed to determine which aspects of the near-storm environment most effectively discriminate between tornadic (or significantly tornadic) and nontornadic storms toward constructing new sounding-derived forecast guidance parameters for multiple modal and environmental combinations. High-shear, high-CAPE (HSHC) environments are contrasted with high-shear, low-CAPE (HSLC) environments to highlight physical processes governing storm maintenance and tornadogenesis in the absence of large instability. Sounding-derived data corresponding to each report are used to characterize how the near-storm environment evolves across the EET, and whether these changes influence the mode, frequency, and tornadic likelihood of their associated storms.
![doppler radar southeastern united states doppler radar southeastern united states](https://i.pinimg.com/originals/57/85/1a/57851a1333fe142548f865911cfdd779.gif)
To disentangle these complex environmental interactions, Southeast severe convective reports spanning 2003–18 are temporally binned relative to local sunset. storm climatology, which includes the increased presence of low-CAPE environments and tornadic nonsupercell modes. We will present preliminary wind retrieval results using these refined techniques.The response of severe local storms to environmental evolution across the early evening transition (EET) remains a forecasting challenge, particularly within the context of the Southeast U.S. Using multi-Doppler and in situ data gathered from the 2017 field phase of the VORTEX-SE project, we are working to refine and improve the accuracy of three-dimensional wind retrieval solutions through incorporation of surface mesonet data and lower boundary conditions representative of terrain features in the southeast.
![doppler radar southeastern united states doppler radar southeastern united states](https://www.datacalltech.com/wp-content/uploads/2016/12/200_NM_65212_Static.jpg)
Extrapolation assumptions that are error prone even in these relatively flat conditions are more problematic in areas with more complex terrain and varied vegetation.
![doppler radar southeastern united states doppler radar southeastern united states](https://techmediaguide.com/wp-content/uploads/2018/12/Doppler-Radar.jpg)
Multiple-Doppler wind retrievals in severe storms, which can contain intense horizontal convergence and updrafts near the ground, often are performed for storms targeted in relatively flat and vegetation-free regions of the Plains. Accurate multiple-Doppler radar wind retrievals require quantification of wind shear below the lowest matched radar scan elevation (often ~100- 300 m AGL even in high-density research deployments). Although three-dimensional wind retrievals from multiple-Doppler radar observations are a common tool for severe storm analyses, few examples have been presented from cases examined in the Southeastern U.S.