Yvette Richardson
· Professor of Meteorology, Associate Dean for Undergraduate Education, Department of Meteorology and Atmospheric ScienceVerifiedPennsylvania State University · Department of Meteorology and Atmospheric Science
Active 1999–2026
About
Yvette Richardson is a Professor of Meteorology and the Senior Associate Dean for Undergraduate Education at the College of Earth and Mineral Sciences at Penn State. Her research specializes in atmospheric dynamics, mesoscale meteorology, and severe weather phenomena, with a particular focus on understanding the formation and evolution of severe storms through both numerical modeling and observational methods. She investigates the influence of environmental shear and convective available potential energy on storm characteristics such as strength, rotation, and longevity. Dr. Richardson's observational work has concentrated on storm rotation, tornado genesis, and maintenance, utilizing mobile radars to collect fine-scale data on thunderstorms and tornadoes. She was a principal investigator in the International H20 Project (IHOP) in 2002, focusing on convection initiation and boundary layer processes, and served as a steering committee member and principal investigator for the second phase of the VORTEX2 project in 2009 and 2010. Recently, she has collaborated on deploying pseudo-Lagrangian balloon-borne sensors into supercell and tornadic storms. Her teaching interests include atmospheric dynamics, mesoscale processes, convection, radar meteorology, and introductory atmospheric science courses.
Research topics
- Physics
- Meteorology
- Geology
- Climatology
- Atmospheric sciences
- Environmental science
- Geodesy
- Mechanics
- Geometry
Selected publications
Monthly Weather Review · 2026-02-25
articleAbstract This case study analyzes a nontornadic supercell observed on 9–10 June 2009 in southwest Kansas during the Verification of the Origins of Rotation in Tornadoes Experiment 2 (VORTEX2). Time-series multi-Doppler radar analyses and diabatic Lagrangian analysis retrievals document the kinematic and thermal–microphysical evolution of the storm’s strengthening low-level mesocyclone during the period 2342–2351 UTC, an apparent “tornadogenesis failure” event around 2351 UTC, and subsequent storm decay through 0024 UTC. An analyzed current of low- and midlevel streamwise vorticity enters the supercell updraft, appearing similar to the streamwise vorticity current (SVC) identified in previous supercell simulations. However, the present SVC primarily feeds into the midlevel updraft and mesocyclone, with relatively limited inflow to the low-level occlusion updraft and mesocyclone. Lagrangian vector vorticity dynamical calculations demonstrate that baroclinity, differential hydrometeor loading, and horizontal stretching all play significant roles in the generation and amplification of streamwise vorticity associated with this SVC. The origins of concentrated vertical vorticity in this mature low-level mesocyclone are consistent with off-trajectory separation of streamwise vorticity in downdraft previously identified in supercell simulations. However, the off-trajectory vorticity vector displacement in the present case is forced by differential hydrometeor loading instead of thermal gradients, since the cold pool is penetrating the low-level mesocyclone core. Another unique feature of this study is the detailed validation of surface radar-derived airflow and retrieved thermal fields with observations from a dense array of surface in situ measurement platforms in the storm. Significance Statement This study investigates the origins of strongly rotating low-altitude winds via airflow, temperature, and precipitation analyses of a nontornadic supercell (a long-lived thunderstorm with rotating updrafts). Although computer simulations provide highly detailed process understanding of complicated supercell evolutions, these simulated processes have been difficult to quantify in real supercells owing to a lack of required observations. We identify “currents” of horizontal vorticity—rotating wind in a vertical plane—that develop along the edges of the supercell’s rain-cooled outflow and precipitation core, similar to previous simulated rotation development processes. These vorticity currents are subsequently tipped in the observed storm’s updraft to impart its vertical rotation, although ingesting cold outflow likely prevents the observed rotating updraft from forming a tornado.
‘Twisters’ movie: Two tornado scientists take us inside the real world of storm chasing
2024-07-11
article1st authorCorrespondingMonthly Weather Review · 2024-03-11 · 1 citations
articleAbstract Previous work found that cold pools in ordinary convection are more sensitive to the microphysics scheme when the lifting condensation level (LCL) is higher owing to a greater evaporation potential, which magnifies microphysical uncertainties. In the current study, we explore whether the same reasoning can be applied to supercellular cold pools. To do this, four perturbed-microphysics ensembles are run, with each using an environment with a different LCL. Similar to ordinary convection, the sensitivity of supercellular cold pools to the microphysics increases with higher LCLs, though the physical reasoning for this increase in sensitivity differs from a previous study. Using buoyancy budgets along parcel trajectories that terminate in the cold pool, we find that negative buoyancy generated by microphysical cooling is partially countered by a decrease in environmental potential temperatures as the parcel descends. This partial erosion of negative buoyancy as parcels descend is most pronounced in the low-LCL storms, which have steeper vertical profiles of environmental potential temperature in the lower atmosphere. When this erosion is accounted for, the strength of the strongest cold pools in the low-LCL ensemble is reduced, resulting in a narrower distribution of cold pool strengths. This narrower distribution is indicative of reduced sensitivity to the microphysics. These results suggest that supercell behavior and supercell hazards (e.g., tornadoes) may be more predictable in low-LCL environments. Significance Statement Thunderstorms typically produce “pools” of cold air beneath them owing in part to the evaporation of rain and melting of ice produced by the storm. Past work has found that in computer simulations of thunderstorms, the cold pools that form beneath thunderstorms are sensitive to how rain and ice are modeled in the simulation. In this study, we show that in the strongest thunderstorms that are capable of producing tornadoes, this sensitivity is reduced when the humidity in the lowest few kilometers above the surface is increased. Exploring why the sensitivity is reduced when the humidity increases provides a deeper understanding of the relationship between humidity and cold pool strength, which is important for severe storm forecasting.
Monthly Weather Review · 2022 · 18 citations
Senior authorCorresponding- Geology
- Meteorology
- Atmospheric sciences
Abstract This study analyzes aboveground thermodynamic observations in three tornadic supercells obtained via swarms of small balloon-borne sondes acting as pseudo-Lagrangian drifters; the storm-relative winds draw the sondes through the precipitation, outflow, and baroclinic zones, which are believed to play key roles in tornado formation. Three-dimensional thermodynamic analyses are produced from the in situ observations. The coldest air is found at the lowest analysis levels, where virtual potential temperature deficits of 2–5 K are observed. Air parcels within the forward-flank outflow are inferred from their equivalent potential temperatures to have descended only a few hundred meters or less, whereas parcels within the rear-flank outflow are inferred to have downward excursions of 1–2 km. Additionally, the parcels following paths toward the low-level mesocyclone pass through horizontal buoyancy gradients that are strongest in the lowest 750 m and estimated to be capable of baroclinically generating horizontal vorticity having a magnitude of 6–10 × 10 −3 s −1 . A substantial component of the baroclinically generated vorticity is initially crosswise, though the vorticity subsequently could become streamwise given the leftward bending of the airstream in which the vorticity is generated. The baroclinically generated vorticity could contribute to tornado formation upon being tilted upward and stretched near the surface beneath a strong, dynamically forced updraft. Significance Statement Swarms of balloon-borne probes are used to produce the first-ever, three-dimensional mappings of temperature from in situ observations within supercell storms (rotating storms with high tornado potential). Temperature has a strong influence on the buoyancy of air, and horizontal variations of buoyancy generate spin about a horizontal axis. Buoyancy is one of the primary drivers of upward and downward motions in thunderstorms, and in supercell storms, horizontally oriented spin can be tipped into the vertical and amplified by certain arrangements of upward and downward motions. Unfortunately, the long-standing lack of temperature observations has hampered scientists’ ability to evaluate computer simulations and the tornadogenesis theories derived from them. We find that significant spin could be generated by the horizontal buoyancy variations sampled by the probes.
Monthly Weather Review · 2022-06-17 · 7 citations
articleAbstract Several studies have documented the sensitivity of convective storm simulations to the microphysics parameterization, but there is less research documenting how these sensitivities change with environmental conditions. In this study, the influence of the lifting condensation level (LCL) on the sensitivity of simulated ordinary convective storm cold pools to the microphysics parameterization is examined. To do this, seven perturbed-microphysics ensembles with nine members each are used, where each ensemble uses a different base state with a surface-based LCL between 500 and 2000 m. A comparison of ensemble standard deviations of cold-pool properties shows a clear trend of increasing sensitivity to the microphysics as the LCL is raised. In physical terms, this trend is the result of lower relative humidities in high-LCL environments that increase low-level rain evaporational cooling rates, which magnifies differences in evaporation already present among the members of a given ensemble owing to the microphysics variations. Omitting supersaturation from the calculation of rain evaporation so that only the raindrop size distribution influences evaporation leads to more evaporation in the low-LCL simulations (owing to more drops), as well as a slightly larger spread in evaporational cooling amounts between members in the low-LCL ensembles. Cold pools in the low-LCL environments are also found to develop earlier and are initially more sensitive to raindrop breakup owing to a larger warm-cloud depth. Altogether, these results suggest that convective storms may be more predictable in low-LCL environments, and forecasts of convection in high-LCL environments may benefit the most from microphysics perturbations within an ensemble forecasting system. Significance Statement Computer simulations of thunderstorms can have grid spacings ranging from tens to thousands of meters. Because individual precipitation particles form on scales smaller than these grid spacings, the bulk effects of precipitation processes in models must be approximated. Past studies have found that models are sensitive to these approximations. In this study, we test whether the sensitivity to these approximations changes with the relative humidity in the lowest 1–2 km of the atmosphere. We found that increasing the relative humidity decreases the sensitivity of simulations to the precipitation process approximations. These results can inform meteorologists about the uncertainties surrounding computer-generated thunderstorm forecasts and suggest environmental conditions where using several computer models with different precipitation process approximations may be beneficial.
Journal of the Atmospheric Sciences · 2021-09-15 · 5 citations
articleAbstract Convective inhibition (CIN) is one of the parameters used by forecasters to determine the inflow layer of a convective storm, but little work has examined the best way to compute CIN. One decision that must be made is whether to lift parcels following a pseudoadiabat (removing hydrometeors as the parcel ascends) or reversible moist adiabat (retaining hydrometeors). To determine which option is best, idealized simulations of ordinary convection are examined using a variety of base states with different reversible CIN values for parcels originating in the lowest 500 m. Parcel trajectories suggest that ascent over the lowest few kilometers, where CIN is typically accumulated, is best conceptualized as a reversible moist adiabatic process instead of a pseudoadiabatic process. Most inflow layers do not contain parcels with substantial reversible CIN, despite these parcels possessing ample convective available potential energy and minimal pseudoadiabatic CIN. If a stronger initiation method is used, or hydrometeor loading is ignored, simulations can ingest more parcels with large amounts of reversible CIN. These results suggest that reversible CIN, not pseudoadiabatic CIN, is the physically relevant way to compute CIN and that forecasters may benefit from examining reversible CIN instead of pseudoadiabatic CIN when determining the inflow layer.
E-Journal of Severe Storms Meteorology · 2021 · 41 citations
- Geology
- Meteorology
- Geodesy
The three-dimensional wind fields within three nontornadic supercell thunderstorms are retrieved from dual-Doppler radar observations obtained by a pair of Doppler on Wheels (DOW) radars. The observations focus on the low-level mesocyclone regions of the storms near the time of strongest low-level rotation. All three storms display strong low-level rotation (e.g., the vertical vorticity maxima exceed 0.05 s-1 in the lowest 1000 m AGL in each storm). A principal finding is that the nontornadic mesocyclones possess many of the same signatures found in tornadic supercells, even those viewed in similarly fine resolution; e.g., rear-flank gust fronts wrapping around the circulation centers, multiple cyclonic vertical vorticity maxima along the gust front that spiral inward toward the circulation center, and arching vortex lines joining the cyclonic vorticity maxima to regions of anticyclonic vertical vorticity on the opposite side of the hook echo. The nontornadic mesocyclones possess less circulation than most of the tornadic mesocyclones that have been observed by the DOW radars, particularly within 1 km of the axis of rotation. Another finding is that the trajectories of air parcels passing through the near-surface vertical vorticity maxima have relatively shallow upward vertical excursions, suggesting that these parcels do not enter the overlying midlevel updraft and mesocyclone.
Processes Preventing the Development of a Significant Tornado in a Colorado Supercell on 26 May 2010
Monthly Weather Review · 2020 · 15 citations
- Meteorology
- Atmospheric sciences
- Geology
Abstract A supercell produced a nearly tornadic vortex during an intercept by the Second Verification of the Origins of Rotation in Tornadoes Experiment on 26 May 2010. Using observations from two mobile radars performing dual-Doppler scans, a five-probe mobile mesonet, and a proximity sounding, factors that prevented this vortex from strengthening into a significant tornado are examined. Mobile mesonet observations indicate that portions of the supercell outflow possessed excessive negative buoyancy, likely owing in part to low boundary layer relative humidity, as indicated by a high environmental lifted condensation level. Comparisons to a tornadic supercell suggest that the Prospect Valley storm had enough far-field circulation to produce a significant tornado, but was unable to converge this circulation to a sufficiently small radius. Trajectories suggest that the weak convergence might be due to the low-level mesocyclone ingesting parcels with considerable crosswise vorticity from the near-storm environment, which has been found to contribute to less steady and weaker low-level updrafts in supercell simulations. Yet another factor that likely contributed to the weak low-level circulation was the inability of parcels rich in streamwise vorticity from the forward-flank precipitation region to reach the low-level mesocyclone, likely owing to an unfavorable pressure gradient force field. In light of these results, we suggest that future research should continue focusing on the role of internal, storm-scale processes in tornadogenesis, especially in marginal environments.
Data Commons · 2020-02-27
datasetOpen accessThese data and computer codes contained in this zip file were used in an analysis of a supercell on 26 May 2010 near Prospect Valley, Colorado, that was intercepted by the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2). The results from this analysis are discussed in the following journal article: Murdzek, S. S., P. M. Markowski, Y. P. Richardson, R.L. Tanamachi, 2020: Processes preventing the development of a significant tornado in a Colorado supercell on 26 May 2010. Monthly Weather Review, Article DOI: 10.1175/MWR-D-19-0288.1
Monthly Weather Review · 2020-10-06 · 13 citations
articleOpen accessSenior authorAbstract Recent high-resolution numerical simulations of supercells have identified a feature referred to as the streamwise vorticity current (SVC). Some have presumed the SVC to play a role in tornadogenesis and maintenance, though observations of such a feature have been limited. To this end, 125-m dual-Doppler wind syntheses and mobile mesonet observations are used to examine three observed supercells for evidence of an SVC. Two of the three supercells are found to contain a feature similar to an SVC, while the other supercell contains an antistreamwise vorticity ribbon on the southern fringe of the forward flank. A closer examination of the two supercells with SVCs reveals that the SVCs are located on the cool side of boundaries within the forward flank that separate colder, more turbulent flow from warmer, more laminar flow, similar to numerical simulations. Furthermore, the observed SVCs are similar to those in simulations in that they appear to be associated with baroclinic vorticity generation and have similar appearances in vertical cross sections. Aside from some apparent differences in the location of the maximum streamwise vorticity between simulated and observed SVCs, the SVCs seen in numerical simulations are indeed similar to reality. The SVC, however, may not be essential for tornadogenesis, at least for weak tornadoes, because the supercell that did not have a well-defined SVC produced at least one brief, weak tornado during the analysis period.
Recent grants
NSF · $510k · 2005–2009
Improving our Understanding of Tornadic Storms using VORTEX2 Observations and Idealized Simulations
NSF · $932k · 2015–2020
NSF · $1.0M · 2008–2013
NSF · $1.1M · 2012–2017
NSF · $330k · 2007–2011
Frequent coauthors
- 52 shared
Paul Markowski
Pennsylvania State University
- 39 shared
Joshua Wurman
University of Illinois Urbana-Champaign
- 31 shared
Richard L. Thompson
NOAA Storm Prediction Center
- 31 shared
Andrew R. Dean
NOAA Storm Prediction Center
- 31 shared
Bryan T. Smith
NOAA Storm Prediction Center
- 31 shared
Alexandra K. Anderson-Frey
University of Washington
- 16 shared
David C. Dowell
NOAA Earth System Research Laboratory
- 16 shared
Paul Robinson
University of Illinois Urbana-Champaign
Awards & honors
- VORTEX2 (2009 and 2010)
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