@article{peters_chavas_su_morrison_coffer_2023, title={An Analytic Formula for Entraining CAPE in Midlatitude Storm Environments}, volume={80}, ISSN={["1520-0469"]}, DOI={10.1175/JAS-D-23-0003.1}, abstractNote={
This article introduces an analytic formula for entraining convective available potential energy (ECAPE) with an entrainment rate that is determined directly from an environmental sounding, rather than prescribed by the formula user. Entrainment is connected to the background environment using an eddy diffusivity approximation for lateral mixing, updraft geometry assumptions, and mass continuity. These approximations result in a direct correspondence between the storm relative flow and the updraft radius and an inverse scaling between the updraft radius squared and entrainment rate. The aforementioned concepts, combined with the assumption of adiabatic conservation of moist static energy, yield an explicit analytic equation for ECAPE that depends entirely on state variables in an atmospheric profile and a few constant parameters with values that are established in past literature. Using a simplified Bernoulli-like equation, the ECAPE formula is modified to account for updraft enhancement via kinetic energy extracted from the cloud’s background environment. CAPE and ECAPE can be viewed as predictors of the maximum vertical velocity wmax in an updraft. Hence, these formulas are evaluated using wmax from past numerical modeling studies. Both of the new formulas improve predictions of wmax substantially over commonly used diagnostic parameters, including undiluted CAPE and ECAPE with a constant prescribed entrainment rate. The formula that incorporates environmental kinetic energy contribution to the updraft correctly predicts instances of exceedance of by wmax, and provides a conceptual explanation for why such exceedance is rare among past simulations. These formulas are potentially useful in nowcasting and forecasting thunderstorms and as thunderstorm proxies in climate change studies.}, number={9}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Peters, John M. and Chavas, Daniel R. and Su, Chun -Yian and Morrison, Hugh and Coffer, Brice E.}, year={2023}, month={Sep}, pages={2165–2186} }
 @article{peters_coffer_parker_nowotarski_mulholland_nixon_allen_2023, title={Disentangling the Influences of Storm-Relative Flow and Horizontal Streamwise Vorticity on Low-Level Mesocyclones in Supercells}, volume={80}, ISSN={["1520-0469"]}, DOI={10.1175/JAS-D-22-0114.1}, abstractNote={
Sufficient low-level storm-relative flow is a necessary ingredient for sustained supercell thunderstorms and is connected to supercell updraft width. Assuming a supercell exists, the role of low-level storm-relative flowin regulating supercells’ low-level mesocyclone intensity is less clear. One possibility considered in this article is that storm-relative flow controls mesocyclone and tornado width via its modulation of overall updraft extent. This hypothesis relies on a previously postulated positive correspondence between updraft width, mesocyclone width, and tornado width. An alternative hypothesis is that mesocyclone characteristics are primarily regulated by horizontal streamwise vorticity irrespective of storm-relative flow. A matrix of supercell simulations were analyzed to address the aforementioned hypotheses, wherein horizontal streamwise vorticity and storm-relative flow were independently varied. Among these simulations, mesocyclone width and intensity were strongly correlated with horizontal streamwise vorticity, and comparatively weakly correlated with storm-relative flow, supporting the second hypothesis. Accompanying theory and trajectory analysis offers the physical explanation that, when storm-relative flow is large and updrafts are wide, vertically tilted streamwise vorticity is projected over a wider area but with a lesser average magnitude than when these parameters are small. These factors partially offset one another, degrading the correspondence of storm-relative flow with updraft circulation and rotational velocity, which are the mesocyclone attributes most closely tied to tornadoes. These results refute the previously purported connections between updraft width, mesocyclone width, and tornado width, and emphasize horizontal streamwise vorticity as the primary control on low-level mesocyclones in sustained supercells.}, number={1}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Peters, John M. M. and Coffer, Brice E. E. and Parker, Matthew D. D. and Nowotarski, Christopher J. J. and Mulholland, Jake P. P. and Nixon, Cameron J. J. and Allen, John T. T.}, year={2023}, month={Jan}, pages={129–149} }
 @article{loeffler_kumjian_markowski_coffer_parker_2023, title={Investigating the Relationship between Polarimetric Radar Signatures of Hydrometeor Size Sorting and Tornadic Potential in Simulated Supercells}, volume={151}, ISSN={["1520-0493"]}, DOI={10.1175/MWR-D-22-0228.1}, abstractNote={
The national upgrade of the operational weather radar network to include polarimetric capabilities has lead to numerous studies focusing on polarimetric radar signatures commonly observed in supercells. One such signature is the horizontal separation of regions of enhanced differential reflectivity (ZDR) and specific differential phase (KDP) values due to hydrometeor size sorting. Recent observational studies have shown that the orientation of this separation tends to be more perpendicular to storm motion in supercells that produce tornadoes. Although this finding has potential operational utility, the physical relationship between this observed radar signature and tornadic potential is not known. This study uses an ensemble of supercell simulations initialized with tornadic and nontornadic environments to investigate this connection. The tendency for tornadic supercells to have a more perpendicular separation orientation was reproduced, although to a lesser degree. This difference in orientation angles was caused by stronger rearward storm-relative flow in the nontornadic supercells, leading to a rearward shift of precipitation and, therefore, the enhanced KDP region within the supercell. Further, this resulted in an unfavorable rearward shift of the negative buoyancy region, which led to an order of magnitude less baroclinic generation of circulation in the nontornadic simulations compared to tornadic simulations.}, number={7}, journal={MONTHLY WEATHER REVIEW}, author={Loeffler, Scott D. and Kumjian, Matthew R. and Markowski, Paul M. and Coffer, Brice E. and Parker, Matthew D.}, year={2023}, month={Jul}, pages={1863–1884} }
 @article{coffer_parker_peters_wade_2023, title={Supercell Low-Level Mesocyclones: Origins of Inflow and Vorticity}, volume={151}, ISSN={["1520-0493"]}, DOI={10.1175/MWR-D-22-0269.1}, abstractNote={
The development and intensification of low-level mesocyclones in supercell thunderstorms has often been attributed, at least in part, to augmented streamwise vorticity generated baroclinically in the forward flank of supercells. However, the ambient streamwise vorticity of the environment (often quantified via storm-relative helicity), especially near the ground, is particularly skillful at discriminating between nontornadic and tornadic supercells. This study investigates whether the origins of the inflow air into supercell low-level mesocyclones, both horizontally and vertically, can help explain the dynamical role of environmental versus storm-generated vorticity in the development of low-level mesocyclone rotation. Simulations of supercells, initialized with wind profiles common to supercell environments observed in nature, show that the air bound for the low-level mesocyclone primarily originates from the ambient environment (rather than from along the forward flank) and from very close to the ground, often in the lowest 200 - 400 m of the atmosphere. Given that the near-ground environmental air comprises the bulk of the inflow into low-level mesocyclones, this likely explains the forecast skill of environmental streamwise vorticity in the lowest few hundred meters of the atmosphere. The low-level mesocyclone does not appear to require much augmentation from the development of additional horizontal vorticity in the forward flank. Instead, the dominant contributor to vertical vorticity within the low-level mesocyclone is from the environmental horizontal vorticity. This study provides further context to the on-going discussion regarding the development of rotation within supercell low-level mesocyclones.}, number={9}, journal={MONTHLY WEATHER REVIEW}, author={Coffer, Brice E. and Parker, Matthew D. and Peters, John M. and Wade, Andrew R.}, year={2023}, month={Sep}, pages={2205–2232} }
 @article{coffer_parker_2022, title={Infrasound signals in simulated nontornadic and pre-tornadic supercells}, volume={151}, ISSN={["1520-8524"]}, DOI={10.1121/10.0009400}, abstractNote={There has been increased interest in improving severe weather detection by supplementing the conventional operational radar network with an infrasound observation network, which may be able to detect distinct sub-audible signatures from tornadic supercells. While there is evidence that tornadic thunderstorms exhibit observable infrasound signals, what is not well-understood is whether these infrasound signals are unique to tornadic supercells (compared to nontornadic supercells) or whether there is useful signal prior to tornadogenesis, which would be most relevant to forecasters. Using simulations of supercells, tailored to represent acoustic waves with frequencies from 0.1 to 2 Hz, spectral analysis reveals that both nontornadic and pre-tornadic supercells produce strikingly similar sound pressure levels at the surface, even in close spatial proximity to the storms (less than 20 km). Sensitivity tests employing varying microphysics schemes also show similar acoustic emissions between supercells. Riming of supercooled water droplets in the upper-troposphere is the sole mechanism generating high-frequency pressure waves in supercells prior to tornadogenesis or during tornadogenesis-failure; however, riming occurs continuously in mature nontornadic and tornadic supercells. Our simulations found no clear evidence that infrasound produced by supercells prior to tornado formation (compared to nontornadic supercells) is sufficiently distinct to improve lead-time of tornado warnings.}, number={2}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Coffer, Brice E. and Parker, Matthew D.}, year={2022}, month={Feb}, pages={939–954} }
 @article{flournoy_coniglio_rasmussen_furtado_coffer_2020, title={Modes of Storm-Scale Variability and Tornado Potential in VORTEX2 Near- and Far-Field Tornadic Environments}, volume={148}, ISSN={["1520-0493"]}, DOI={10.1175/MWR-D-20-0147.1}, abstractNote={Some supercellular tornado outbreaks are composed almost entirely of tornadic supercells, while most consist of both tornadic and nontornadic supercells sometimes in close proximity to each other. These differences are related to a balance between larger-scale environmental influences on storm development as well as more chaotic, internal evolution. For example, some environments may be potent enough to support tornadic supercells even if less predictable intrastorm characteristics are suboptimal for tornadogenesis, while less potent environments are supportive of tornadic supercells given optimal intrastorm characteristics. This study addresses the sensitivity of tornadogenesis to both environmental characteristics and storm-scale features using a cloud modeling approach. Two high-resolution ensembles of simulated supercells are produced in the near- and far-field environments observed in the inflow of tornadic supercells during the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2). All simulated supercells evolving in the near-field environment produce a tornado, and 33% of supercells evolving in the far-field environment produce a tornado. Composite differences between the two ensembles are shown to address storm-scale characteristics and processes impacting the volatility of tornadogenesis. Storm-scale variability in the ensembles is illustrated using empirical orthogonal function analysis, revealing storm-generated boundaries that may be linked to the volatility of tornadogenesis. Updrafts in the near-field ensemble are markedly stronger than those in the far-field ensemble during the time period in which the ensembles most differ in terms of tornado production. These results suggest that storm-environment modifications can influence the volatility of supercellular tornadogenesis.}, number={10}, journal={MONTHLY WEATHER REVIEW}, author={Flournoy, Matthew D. and Coniglio, Michael C. and Rasmussen, Erik N. and Furtado, Jason C. and Coffer, Brice E.}, year={2020}, month={Oct}, pages={4185–4207} }
 @article{coffer_taszarek_parker_2020, title={Near Ground Wind Profiles of Tornadic and Nontornadic Environments in the United States and Europe from ERAS Reanalyses}, volume={35}, ISSN={["1520-0434"]}, DOI={10.1175/WAF-D-20-0153.1}, abstractNote={The near-ground wind profile exhibits significant control over the organization, intensity, and steadiness of low-level updrafts and mesocyclones in severe thunderstorms, and thus their probability of being associated with tornadogenesis. The present work builds upon recent improvements in supercell tornado forecasting by examining the possibility that storm-relative helicity (SRH) integrated over progressively shallower layers has increased skill in differentiating between significantly tornadic and nontornadic severe thunderstorms. For a population of severe thunderstorms in the United States and Europe, sounding-derived parameters are computed from the ERA5 reanalysis, which has significantly enhanced vertical resolution compared to prior analyses. The ERA5 is shown to represent U.S. convective environments similarly to the Storm Prediction Center’s mesoscale surface objective analysis, but its greater number of vertical levels in the lower troposphere permits calculations to be performed over shallower layers. In the ERA5, progressively shallower layers of SRH provide greater discrimination between nontornadic and significantly tornadic thunderstorms in both the United States and Europe. In the United States, the 0–100 m AGL layer has the highest forecast skill of any SRH layer tested, although gains are comparatively modest for layers shallower than 0–500 m AGL. In Europe, the benefit from using shallower layers of SRH is even greater; the lower-tropospheric SRH is by far the most skillful ingredient there, far exceeding related composite parameters like the significant tornado parameter (which has negligible skill in Europe).}, number={6}, journal={WEATHER AND FORECASTING}, author={Coffer, Brice E. and Taszarek, Mateusz and Parker, Matthew D.}, year={2020}, month={Dec}, pages={2621–2638} }
 @article{coffer_parker_thompson_smith_jewell_2019, title={Using Near-Ground Storm Relative Helicity in Supercell Tornado Forecasting}, volume={34}, ISSN={["1520-0434"]}, DOI={10.1175/WAF-D-19-0115.1}, abstractNote={Abstract}, number={5}, journal={WEATHER AND FORECASTING}, author={Coffer, Brice E. and Parker, Matthew D. and Thompson, Richard L. and Smith, Bryan T. and Jewell, Ryan E.}, year={2019}, month={Oct}, pages={1417–1435} }
 @article{coffer_markowski_2018, title={Comments on "The Regulation of Tornado Intensity by Updraft Width"}, volume={75}, DOI={10.1175/JAS-D-18-0170.1}, abstractNote={In a recent article, Trapp et al. (2017, hereinafter T17) presented a theoretical case based on Kelvin’s circulation theorem to argue that wider updrafts are more likely to be associated with strong to violent tornadoes [enhanced Fujita (EF) ratings. 2] than narrower updrafts. They then presented idealized numerical simulations of supercell thunderstorms to support their contention. In their suite of simulated supercells, updraft area was highly correlated with midlevel mesocyclone area, downdraft area, and near-ground vertical vorticity magnitude. Larger midlevel mesocyclones were also strongly correlated with larger near-ground mesocyclones. The implications of their findings are potentially important, owing to the possibility of routinely measuring updraft widths in satellite imagery. Herein, we hope to shed additional light on the generality of their findings by presenting the relationships between updraft, downdraft, and mesocyclone area from a higher-resolution ensemble of nontornadic and tornadic supercells.}, number={11}, journal={JOURNAL OF THE ATMOSPHERIC SCIENCES}, author={Coffer, Brice E. and Markowski, Paul M.}, year={2018}, pages={4049–4056} }
 @article{coffer_parker_dahl_wicker_clark_2017, title={Volatility of Tornadogenesis: An Ensemble of Simulated Nontornadic and Tornadic Supercells in VORTEX2 Environments}, volume={145}, ISSN={["1520-0493"]}, DOI={10.1175/mwr-d-17-0152.1}, abstractNote={ Despite an increased understanding of the environments that favor tornado formation, a high false-alarm rate for tornado warnings still exists, suggesting that tornado formation could be a volatile process that is largely internal to each storm. To assess this, an ensemble of 30 supercell simulations was constructed based on small variations to the nontornadic and tornadic environmental profiles composited from the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2). All simulations produce distinct supercells despite occurring in similar environments. Both the tornadic and nontornadic ensemble members possess ample subtornadic surface vertical vorticity; the determinative factor is whether this vorticity can be converged and stretched by the low-level updraft. Each of the 15 members in the tornadic VORTEX2 ensemble produces a long-track, intense tornado. Although there are notable differences in the precipitation and near-surface buoyancy fields, each storm features strong dynamic lifting of surface air with vertical vorticity. This lifting is due to a steady low-level mesocyclone, which is linked to the ingestion of predominately streamwise environmental vorticity. In contrast, each nontornadic VORTEX2 simulation features a supercell with a disorganized low-level mesocyclone, due to crosswise vorticity in the lowest few hundred meters in the nontornadic environment. This generally leads to insufficient dynamic lifting and stretching to accomplish tornadogenesis. Even so, 40% of the nontornadic VORTEX2 ensemble members become weakly tornadic. This implies that chaotic within-storm details can still play a role and, occasionally, lead to marginally tornadic vortices in suboptimal storms. }, number={11}, journal={MONTHLY WEATHER REVIEW}, author={Coffer, Brice E. and Parker, Matthew D. and Dahl, Johannes M. L. and Wicker, Louis J. and Clark, Adam J.}, year={2017}, month={Nov}, pages={4605–4625} }
 @article{rohi_ramezani_rahmaninia_zabihzadeh_hubbe_2016, title={Influence of pulp suspension ph on the performance of chitosan as a strength agent for hardwood cmp paper}, volume={50}, number={7-8}, journal={Cellulose Chemistry and Technology}, author={Rohi, M. and Ramezani, O. and Rahmaninia, M. and Zabihzadeh, S. M. and Hubbe, M. A.}, year={2016}, pages={873–878} }
 @article{coffer_parker_2015, title={Impacts of Increasing Low-Level Shear on Supercells during the Early Evening Transition}, volume={143}, ISSN={["1520-0493"]}, DOI={10.1175/mwr-d-14-00328.1}, abstractNote={Abstract}, number={5}, journal={MONTHLY WEATHER REVIEW}, author={Coffer, Brice E. and Parker, Matthew D.}, year={2015}, month={May}, pages={1945–1969} }
 @article{clark_coniglio_coffer_thompson_xue_kong_2015, title={Sensitivity of 24-h Forecast Dryline Position and Structure to Boundary Layer Parameterizations in Convection-Allowing WRF Model Simulations}, volume={30}, ISSN={["1520-0434"]}, DOI={10.1175/waf-d-14-00078.1}, abstractNote={Abstract}, number={3}, journal={WEATHER AND FORECASTING}, author={Clark, Adam J. and Coniglio, Michael C. and Coffer, Brice E. and Thompson, Greg and Xue, Ming and Kong, Fanyou}, year={2015}, month={Jun}, pages={613–638} }
 @article{coffer_maudlin_veals_clark_2013, title={Dryline Position Errors in Experimental Convection-Allowing NSSL-WRF Model Forecasts and the Operational NAM}, volume={28}, ISSN={["0882-8156"]}, DOI={10.1175/waf-d-12-00092.1}, abstractNote={Abstract}, number={3}, journal={WEATHER AND FORECASTING}, author={Coffer, Brice E. and Maudlin, Lindsay C. and Veals, Peter G. and Clark, Adam J.}, year={2013}, month={Jun}, pages={746–761} }