ICDS Leadership

About Jenni L. Evans

Current Appointments


View PDF of Jenni Evans’ CV


  • PhD – Monash University (Applied Mathematics)
  • B.Sc. (Honors) – Monash University (Applied Mathematics)



  • Modulation of tropical cyclone (TC) intensity and activity
  • Climate change impacts in the convective tropics
  • Climate change weather impacts in the US

Numerical Weather Prediction:

  • Dynamic evolution of TCs
  • Utilization of ensemble simulations for predictability

Tropical Meteorology:

  • Extratropical transition (ET) of tropical cyclones
  • Tropical cyclogenesis and African Easterly Waves (AEWs)
  • Subtropical cyclone genesis and evolution
  • Factors governing TC intensity and links to the TC boundary layer

Statistical Meteorology:

  • Machine learning approaches for interrogation of ensemble simulations
  • Path clustering using regression mixture models
  • Prediction of significant windspeed radii in a TC using machine learning
  • Climate downscaling
  • Dimension reduction

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Mathematics, meteorology — and even music. Jenni Evans, professor of meteorology and atmospheric science, has forged a career by creatively merging research fields, forging interdisciplinary partnerships and leading those partnerships in tackling complex science and society’s biggest challenges.

Evans was born in Melbourne, Australia, earning both her undergraduate and doctoral degrees in applied mathematics at Monash University.

Originally a math student, Evans attended a weekend field trip to learn how calculus could be employed in understanding the atmosphere. The experience opened her eyes to a career where she could use her passion for math in a practical and challenging way.

During her doctoral studies at Monash University, Evans spent much of her time at the Bureau of Meteorology Research Centre in Melbourne, Australia, and at the Naval Postgraduate School in Monterey, California. After receiving her doctorate in 1990, Evans joined the Commonwealth Scientific and Industrial Research Organisation (CSIRO) as a research scientist; in 1992 she came to Penn State as an assistant professor.

While at Penn State, Evans has taken on many University-wide leadership roles. Evans served as acting director of both the Penn State Institutes for Energy and the Environment, and the Earth and Environmental Systems Institute. In 2017, she was appointed second director of Penn State’s Institute for Computational and Data Sciences (ICDS).

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Research Overview

Evans’ research centers on one of the hottest areas in the atmosphere: weather and climate in the tropics. She and her research team study the fundamentals of tropical cyclone (TC) evolution, from the birth of the TC in the tropics or subtropics, through the life cycle of these potentially devastating storms. More recently, it includes development of machine learning techniques for downscaling climate model simulations to infer changes in local weather. One of the most rewarding aspects of her research career is collaborating with such talented students and other colleagues.

Extratropical Transition (ET) of Tropical Cyclones

A substantial subset (~45% in the North Atlantic) of intense hurricanes undergo a transition in structure – from a relatively symmetric hurricane to an asymmetric extratropical cyclone – as they move out of the tropics. This process is known as extratropical transition, or ET. Hurricane Sandy (2012) is an example of the many ET events occurring each year. Evolution of the structure of the cyclone and its interaction with its environment lead to dramatic differences in the spatial and temporal distribution of the significant weather – intense winds, damaging winds and heavy rains, inland flooding and storm surge, etc. – leading to potentially serious societal impacts.

  • High resolution ensemble of Hurricane Sandy (2012) to explore the mechanisms underlying the warm seclusion (Kowaleski and Evans 2018).
  • Application of the path clustering (mixture model) methodology to ensemble forecasts of Hurricane Sandy (2012), resulting in a robust partition of the ensemble into physically-consistent groups (Kuruppumullage Don et al. 2016).
  • Intercomparison of these groups to identify within-group similarities and between-group differences in the storm and environment leading to a small set of realistic alternative lifecycles for Sandy (Kowaleski and Evans 2016a).

Recent collaborators: Alex Kowaleski, Prabhani Kuruppumullage Don, Francesca Chiaromonte

Extratropical Transition (ET) – Current and Possible Future Climates

Understanding the drivers of extratropical transition in the present climate, and characterizing their structure in a compact way, based on prior work, provides a pathway for developing a methodology for projecting changes in ET for future climates.

  • Community-wide review on the impacts of the storm environment on the outcomes of ET events (Keller et al. 2018).
  • Global climatology of extratropical transition of tropical cyclones using a consistent definition of ET (Bieli et al. 2018a). In this study, ET is defined based on the Cyclone Phase Space (CPS) (Hart 2003; Evans and Hart 2003).
  • Statistical analysis of the effectiveness of the CPS-based definition of ET, compared to the classifications assigned by forecasters in each basin; also examined the sensitivity of the inferred occurrence and timing of the CPS-based ET when two different reanalysis databases are used to calculate the CPS (Bieli et al. 2018b).

Recent collaborators: Julia Keller (and co-authors), Melanie Bielle, Suzana Camargo, Adam Sobel, Tim Hall

Ensemble Forecasting & Partitioning via Machine Learning & Cluster Analysis

Ensemble forecasts provide 10-100s of realizations of the potential future of a system based upon incomplete understanding of its current state. The methodology developed and applied here are demonstrated to give physically-distinct objective partitions of ensembles, greatly reducing (to <10) the set of potential synoptic outcomes to consider, while retaining the uncertainty information encompassed by the full ensemble.

  • Application of point-clustering based validation techniques to ensemble simulations of the structural evolution of Hurricane Sandy (Evans et al. 2015).
  • Development and proof of concept for applying mixture models to ensembles of simulations of purely tropical and extratropical transition cases, deriving physically meaningful partitions that capture the temporal evolution of the system being simulated (Kuruppumullage Don et al. 2016).

Recent collaborators: Prabhani Kuruppumullage Don, Francesca Chiaromonte, Alex Kowaleski

Extended Hurricane Potential Intensity (EPI)

Our work included exploring the impacts of the assumptions on the storm windfield structure (radial profile of tangential wind), as well as the assumptions on the structure of the atmospheric boundary layer and environmental source air. We demonstrated that the EPI could be substantially greater (1–2 Saffir Simpson categories) than PI when this continuous energy flux is accounted for. In this proposal we describe a plan for continuing to develop this theory and to explore its implications.

  • Development of a new composite, observational hurricane boundary layer, with particular focus on the storm and environmental characteristics needed to examine the assumptions underpinning the original PI theory (Kowaleski and Evans 2015).
  • Development of a new “Extended PI (EPI)” that incorporates continuous energy fluxes from the ocean as air flows into the storm (Kowaleski and Evans 2016b).

Recent collaborators: Alex Kowaleski

Organized Convection in the Tropics

Observationally-based analysis of the relationship between tropical convection in the Asian, Australian and African summer monsoons and the underlying sea surface temperature (Evans and Webster 2014).

  • Methodology for detecting, characterizing, and tracking mesoscale convective systems (Nuñez Ocasio et al. 2019).
  • Sensitivity study of the influence of topography on African Easterly Wave energetics and their interactions with mesoscale convective systems (Hamilton et al. 2019).

Recent collaborators: Kelly Nuñez Ocasio, Holly Hamilton, Jose Fuentes, George Young, Casey Webster

The Music of Meteorology

In Memoriam: On 18 July 2019, Mark Ballora was lost to us, silencing the music of hurricanes and leaving a hole in our community.

Unlikely interdisciplinary partnerships can lead to interesting and evocative science. Evans’ work with Mark Ballora, professor of music technology, is one of these quirky collaborations. Ballora’s skill at mapping weather data uniquely to specialized soundscapes – or sonification – creates the music of hurricanes.  By assigning different sounds to key components of hurricanes, such as wind speed, water temperature, symmetry, and latitude, the listener can hear the storm change intensity and structure as it moves out of the tropics and into the cooler water of the higher latitudes.

Here’s a sample. More examples and background on our work is given under Science Communication.

Recent collaborators: Mark Ballora, Alex Kowaleski, David Hughes

Subtropical Cyclones

Extension of previous work (e.g. Evans and Guishard 2009) to examine the factors governing subtropical cyclones in the eastern North Atlantic (González-Alemán et al. 2015).

Analysis of the evolution of Hurricane Alex (2016) in its subtropical phase (González-Alemán et al. 2018).

Recent collaborators: Juan Jesus González-Alemán, Francisco Valero, Francisco Martín-León, Alex Kowaleski

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From Jenni Evans: “Service is at the heart of Penn State’s traditional values of research, teaching and service. I have always worked to tie my scholarship to some of the world’s most pressing problems, such as improving forecasts of tropical cyclones and other intense rain events, contributing to reducing the impacts of TC landfall on economic recovery, and global climate change.

“In my role as director of the Penn State Institute for Computational and Data Sciences, I have the pleasure of working with researchers from 14 colleges and 13 campuses across Penn State. ICDS is charged with enabling interdisciplinary research grounded in cyber-related technologies. ICDS is also building links to industry and to international and US-based universities.

“I was elected Centennial President of the American Meteorological Society, leading the Society in its 100th year.

“As AMS president in 2019, I am working to inspire the AMS membership to expand our vision of the AMS of the future. This vision includes doing even more to help to build societal resilience, while incorporating social justice into our actions. It builds on a long AMS tradition of service to society, but charges our members to take more of a leadership role in convening interdisciplinary and community-based teams to solve complex challenges grounded in weather, water and climate hazards. AMS members are equipped with new capabilities through ever increasing sources of data and computational resources, made even more impactful through advances in the methodologies able to exploit these data and modeling tools most effectively.

“For more than 15 years, I have been Hurricane & Flood Meteorologist for the Professional Team, or Pro Team, for the Florida Commission on Hurricane Loss Projection Methodology (FCHLPM). The Pro Team is tasked with auditing proprietary commercial risk models for assessment of the spatial distribution of risk in Florida due to hurricanes or floods. These risk models are used in setting hurricane insurance rates, so can impact the affordability of housing in Florida. Beyond Penn State, my active service also includes the Earth Sciences Council of the Universities Space Research Association (USRA).”

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Science Communications

A century of the American Meteorological Society (Weather Group Television, May 2019) — On the AMS 100th anniversary

We’re the geeks who have protected the public from weather extremes for 100 years (Newsweek, March 2019) — On the AMS 100th anniversary

Our Ears are Unlocking an Era of Aural Data (Wired, February 2019)
— Author: Clive Thompson; work with Mark Ballora.

Sonification of Hurricanes (Big Ten Network, February 2018) — with Mark Ballora

Sonification of Hurricanes (The Conversation, December 2017) — with Mark Ballora

Hurricanes and Climate Change (Centre County Report, September 2017) — On climate change in the tropics (Author: CommMedia)

Earth Beat on WeatherWorld Climate Change (WPSU Penn State Public Broadcasting, August 2017) — climate change in the tropics

SciTech Now — Sonification (WPSU Penn State Public Broadcasting, August 2017) — with Mark Ballora

Managing Risk in a Changing Climate — (WPSU Penn State Public Broadcasting, April 2017) — interview on a PBS program on climate change mitigation

When Nature Strikes — Science of Natural Hazards: Hurricanes (Collaboration between NBC Learn, NSF and The Weather Channel, July 2015) — episode of a program on natural hazards

Facebook Live interviews with broadcast meteorologists from around the US (American Meteorological Society, June 12-14, 2019) — Topics include AMS, climate change, early career, diversity, and more:

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