A Study of Tornado and Tornadic Thunderstorm Dynamics through High-Resolution Simulation, Advanced Data Assimilation and Prediction

A Proposal Submitted to the

National Science Foundation
In Connection with the VORTEX 2 Field Experiment

Prof. Ming Xue, Principal Investigator
School of Meteorology (SOM) and Center for Analysis and Prediction of Storms (CAPS)
University of Oklahoma (OU)

Dr. Keith Brewster, Co-Principal Investigator
Dr. Jidong Gao, Co-Principal Investigator
Center for Analysis and Prediction of Storms
University of Oklahoma

Proposal No: ATM-0802888
Period of support: 11/15/2008-11/14/2011
Funding level: $780K total (expected)


The tornado is nature’s most violent storm. Tornadoes occur most frequently in the United States and cause millions of dollars of damage and the loss of many lives each year. The tornadogenesis mechanisms are, however, still poorly understood, and the prediction of tornadoes as well as their parent thunderstorms is even more difficult. Much of the challenge comes from the lack of complete observations of the atmospheric state at a sufficiently high resolution.  Often the mesoscale details of the storm environment are also poorly described by available observations. To improve both our understanding of tornadogenesis and our ability to forecast tornadoes and tornadic thunderstorms, the second Verification of the Origin of Rotation in Tornadoes Experiment (VORTEX2, V2 hereafter) is being planed to occur in the Spring of 2009 and 2010. The field experiment promises to collect unprecedented observations at the scales of convective storms and tornadoes and of their environment. Such observations are well suited for initializing storm-scale numerical weather prediction (NWP) models, evaluating the quality of data assimilation, and verifying/validating simulation and prediction results, in addition to being useful for direct analysis of tornadic features and dynamics using the data.

Through this proposal, a team from the Center for Analysis and Prediction of Storms (CAPS) seeks funding to support its participation in V2 field experiment and to conduct related research in four principal areas: 1) Participating in the field-phase of the V2 project through generation of real-time high-resolution (1-2 km) storm-scale ensemble and deterministic forecasts; 2) Conducting ultra-high (down to few meters) resolution numerical simulation experiments for V2 tornado cases for dynamic understanding (including testing of tornadogenesis hypotheses), cross-validations between conceptual models, simulations and fine-scale observations, and for ultimately improving tornado prediction and warning; 3) Studying the impact of microphysical processes and their parameterizations on thunderstorm downdraft, cold pool, and gust front dynamics and their roles in tornadogenesis; 4) Assimilating, using systems that include multi-moment microphysics, routine and special field experiment observations into very-high-resolution four-dimensional data sets for the understanding of dynamics as well as predictability at the thunderstorm through tornado scales, and for studying the impact of special field experiment data on NWP and investigating initial condition sensitivities. The project will leverage on nearly two decades of pioneering research in storm-scale data assimilation and NWP by CAPS and the project team. The project will take advantage of much of the recent progress in storm-scale and radar data assimilation, the increased supercomputing capabilities, and the unique data sets to be collected in V2.

Intellectual merit: The project is expected to contribute significantly to the mission of V2, that is, to answer many of the scientific questions concerning tornadogenesis and decay, tornadic thunderstorm dynamics and their interaction with storm environment, the role of microphysical processes within tornadic thunderstorms, and the predictability of tornadoes and tornadic thunderstorms. The new knowledge and understanding gained will allow us to better assess the likelihood of tornadoes in supercell thunderstorms and thus will lead to advances in forecasting tornado intensity and longevity, using both empirical/statistical and numerical methods. A better understanding of the relationships among tornadoes, their parent thunderstorms, and the larger-scale environment can have broader impacts such as understanding the impact of potential climate change on tornado intensity, frequency and geographical distribution. The improvement to storm-scale data assimilation and modeling capabilities will have a direct positive impact on operational prediction of high-impact hazardous weather.

Broader Impacts:  The proposed research will directly address one of the most important goals of weather research – to improve our ability to accurately predict intense hazardous weather that negatively impacts the American economy and the lives of its citizens, causing large monetary loss and the loss of many lives each year. This project will expose graduate students and young post-doctoral scientists to a major scientific field experiment and give them hands-on experiences working with experimental data sets. It will provide much needed education and training for them in the increasingly important areas of advanced data assimilation and high-resolution simulation and NWP. The research findings will have a direct path to operations through the group's work with operational data assimilation systems (GSI for Rapid Refresh) and prediction models (WRF for RR and NAM), and through their significant role in the NOAA Hazardous Weather Testbed (HWT) Spring Forecast Experiments. The latter exposes operational weather forecasters, as well as university scientists, to cutting-edge forecasting capabilities and products.