We specialize in using numerical models to increase understanding of and improve our ability to predict high-impact weather features, particularly hurricanes and severe storms. Our research interests in these areas are fairly broad, with current emphases including tropical-midlatitude flow interactions, tropical storm intensity change over land, thunderstorm environment classification and forecast sensitivity, and mesoscale convective system structural morphology. If you’re interested in anything we’re working on, let’s talk!
Tropical Cyclone-Midlatitude Flow Interactions
The interaction of a tropical cyclone with the antecedent midlatitude pattern can reconfigure the downstream flow over one or more synoptic-scale wavelengths. This interaction has primarily been conceptualized as being driven by cyclone-scale diabatic processes: first the vertical redistribution of potential vorticity that results in low potential-vorticity air near the tropopause, followed by the advection of this low potential-vorticity air toward the midlatitude waveguide by the tropical cyclone’s outflow. Our group is using thunderstorm-resolving numerical simulations to study whether and how the thunderstorm-scale horizontal rearrangement of potential vorticity, which typically favors low potential-vorticity air on the midlatitude-waveguide side of a thunderstorm’s updraft, may influence this interaction.
Overland Tropical Cyclone Intensity Change
Tropical cyclones are primarily fueled by enthalpy fluxes from an underlying warm ocean. However, some tropical cyclones have reintensified over land, where relatively high friction and a reduced ability to extract enthalpy from the underlying surface typically result in tropical cyclones decaying in the absence of baroclinic forcing (e.g., large-scale forcing for ascent from an upstream trough). Although it is generally accepted that making the surface more water-like is needed to permit for a tropical cyclone to reintensify over land, the precise processes at the land-surface interface and in the upper soil that can result in a tropical cyclone intensifying over land are not yet agreed upon. Our group uses both idealized and real-data numerical simulations to better quantify these processes and their predictability.
Thunderstorm Environments and Predictability
Successful predictions of thunderstorms and their hazards are reliant upon accurate depictions of their mesoscale environments. Our group conducts research to objectively classify soundings within and beyond thunderstorm-supporting environments, document storm-scale ensemble-derived forecast sensitivities and their implications for reliably identifying targeted observations for improving forecast skill, and to identify fundamental shortcomings in high-resolution numerical models (such as how they represent sea-surface temperatures) that limit predictive skill across a wide range of thunderstorm environments.
Mesoscale Convective Systems
Mesoscale convective systems are important contributors to the warm-season precipitation climatology of the central and eastern United States. We are particularly interested in the structure and evolution of rear-inflow jets, which typically form as a mesoscale convective system initially becomes tilted against the direction of the environmental vertical wind shear. Our group is using idealized numerical simulations to better understand how rear-inflow jets evolve in response to environmental changes mimicking those which mesoscale convective systems experience at night. We will soon begin a study in which we quantify the contributions of convectively generated gravity waves, line-end vortices, and the environmental flow to this rear inflow. Our group is also interested in how MCS intensity, structure, and propagation are influenced by mesoscale environmental heterogeneity, particularly as MCSs cross shorelines.
For a full publication listing with accessible summaries, please see the Publications page. A simple publication listing is available in Prof. Evans’ Curriculum Vita. Citation information is available in Prof. Evans’ Google Scholar profile.
Prince and Evans (2022)
J. Atmos. Sci.
- Convectively generated negative potential vorticity enhancing the jet stream through an inverse energy cascade during the extratropical transition of hurricane Irma
Sarro and Evans (2022)
Mon. Wea. Rev.
- An updated investigation of post-transformation intensity, structural, and duration extremes for extratropically transitioning North Atlantic tropical cyclones
Prince and Evans (2020)
Mon. Wea. Rev.
- A climatology of indirect tropical cyclone interactions in the North Atlantic and western North Pacific basins | local PDF copy
Schaffer et al. (2020)
Mon. Wea. Rev.
- Development and evaluation of an evolutionary programming-based tropical cyclone intensity model | local PDF copy
Evans et al. (2018)