My research involves severe storms at all stages of their life, from initiation through the maintenance and demise of tornadoes.
Convection Initiation
During the International H2O Project (IHOP_2002), I was the lead PI for the Doppler on Wheels (DOW) mobile radars in collaboration with Joshua Wurman. We used the DOWs to study how storms form by combining dual-Doppler wind fields with in situ thermodynamic data collected by instrumented cars and rawinsondes. In particular, we investigated the modification of vertical motion and water vapor along boundaries when small-scale vortices (misocyclones) are present. These studies were done in collaboration with Conrad Ziegler of the National Severe Storms Laboratory and PSU masters students James Marquis, Nettie Arnott, Ryan Hastings, Ben Scarino, and Brian Monahan. I later collaborated with David Stensrud and Paul Markowski on a NOAA R2O grant, and my component of the study looked at convection initiation in operational models with my student, Eli Dennis.
Tornadoes
I saw my first tornado on 26 April 1991 on a storm chase with Jerry Straka and Kathy Kanak. A few years later, as a graduate student, I participated in the Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX). Later, I began studying tornadoes in my own research, as a post-doc with Joshua Wurman at the University of Oklahoma, by participating in two seasons of the Radar Observations of Tornadoes and Thunderstorms Experiment (ROTATE, 2000, 2001). I found the challenge of collecting dual-Doppler data on such a rare and fleeting target incredibly interesting. After joining Penn State, I joined several other scientists to form the steering committee for the second VORTEX which came to fruition in 2009 and 2010. We spent years analyzing fascinating data from the VORTEX2 experiment to understand how tornadoes form, how they are maintained, and what ultimately leads to their death. This work was done in collaboration with Paul Markowski, James Marquis, Joshua Wurman, Alicia Klees, Timothy Hatlee, Ryan Hastings, Karen Kosiba, Shawn Murdzek, Patrick Skinner, and Chris Weiss. In 2014, Paul Markowski and I collaborated on highly idealized simulations of storms to clarify the role of the LCL and low-level shear on vortex formation. It’s one of my favorite studies. Recently, our Ph.D. student, Shawn Murdzek, has further clarified how the LCL can affect the sensitivity of simulated cold pools to the microphysics parameterization.
Severe Storms and their Environments
As a Ph.D. student searching for a topic, I was observing a growing thunderstorm and was struck with the question “What if it forms in one type of environment and moves into a different environment?” This led to my dissertation work in which I numerically modeled storms traversing a spatially variable environment. I also varied the environment temporally (with no spatial variations) to examine storm response to a changing hodograph. The latter work was expanded by my student Jaclyn Kost in her masters work. Changing environments remain a fascinating topic to me, and I am currently continuing this work. My Ph.D. student, Alexandra Anderson-Frey, used self-organizing maps to further investigate environmental patterns surrounding tornadic storms. We did this work in a great collaboration with scientists at the Storm Prediction Center.