The Observing System Research and Predictability Experiment (THORPEX) is an international research and development program conducted under the auspice of the World Weather Research Programme (WWRP) of the World Meteorological Organization (WMO), with the goal to accelerate the improvements in the accuracy of one-day to two-week high-impact weather forecasts for the benefit of society, the economy, and the environment. THORPEX was launched in 2004 and is scheduled to conclude in 2014.

Under THORPEX, interactions between the weather research and operational communities have significantly increased worldwide. Numerous science symposia, workshops, working group meetings, and training programs have been conducted to promote and coordinate weather forecast research and help transition research products into operations. The THORPEX Interactive Grand Global Ensemble (TIGGE; Bougeault et al. 2010) archive has been established to provide academic researchers ready access to ensemble forecast products from multiple operational forecast centers. Major international field campaigns and programs, such as the North Atlantic THORPEX Regional Campaign (NA-TReC), the THORPEX Pacific Asian Regional Campaign (TPARC), and the Year of Tropical Convection [YOTC; a program conducted under the joint sponsorship of WWRP/THORPEX and the World Climate Research Programme (WCRP); Waliser et al. 2012], have been conducted. In the United States, THORPEX encouraged collaborations between scientists engaged in research in atmospheric processes and phenomena, the science of prediction, and socioeconomic research and applications (Fig. 1); and contributed to the establishment of the North American Ensemble Forecast System (NAEFS), the implementation of the ensemble-based hybrid Gridpoint Statistical Interpolation–ensemble Kalman filter (GSI-EnKF) data assimilation system at the National Centers for Environmental Prediction, and the establishment of the Winter Storm Reconnaissance (WSR) program by the National Weather Service.

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A schematic emphasizing the intrinsic interconnectedness of U.S. THORPEX. Accelerating the rate of forecast improvement requires the coordination of the prediction science, process and phenomena, and socioeconomic research communities. Adopted from the U.S. THORPEX Science Plan (available from www.ucar.edu/na-thorpex/about.html; the plan was drafted by the U.S. THORPEX Science Steering Committee, formerly chaired by Jim Hansen).

Citation: Bulletin of the American Meteorological Society 94, 11; 10.1175/BAMS-D-13-00057.1

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With THORPEX nearing its conclusion, WWRP recently initiated two new international projects—the Polar Prediction Project (PPP) and the Subseasonal to Seasonal (S2S) project. A third major project has been proposed to complement PPP and S2S by focusing on improving forecasts of high-impact weather events and their impacts on time scales from minutes to weeks. The THORPEX town hall meeting, which was part of the 2013 AMS Annual Meeting, was organized by the U.S. THORPEX Science Steering Committee to provide input into an international planning workshop conducted in Karlsruhe, Germany, during 18–19 March 2013 to further discuss the proposed project and initiate the development of a project plan.

During the town hall meeting, a recurring theme emphasized by many participants was that no one country has the capability to solve the weather forecasting problem on its own. THORPEX has invigorated international collaboration between the best scientists around the world, and the community should work hard to continue this momentum. Such opportunities in leveraging international expertise and resources should be emphasized by scientists participating in THORPEX legacy projects to make a compelling case to funding agencies (both in the United States and internationally) to support these projects.

Speakers at the town hall meeting pointed out that several recent U.S. government agency initiatives are highly relevant to the proposed high-impact weather project as well as the PPP and S2S projects. The Earth System Prediction Capability (ESPC) effort is a collaborative effort between the National Oceanic and Atmospheric Administration (NOAA), U.S. Navy and Air Force, the Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the National Science Foundation (NSF) to promote the development of an Earth system analysis and prediction system, especially focusing on the challenging time scales of the weather to climate interface. Another initiative, NOAA's Weather Ready Nation (WRN), is an effort to build community resilience in the face of increasing vulnerability to extreme weather and water events. Participants remarked that such agency efforts should be leveraged in the development of the new project.

Other speakers promoted the use of operational models in academic research where appropriate in order to streamline the research to the operations transition process. A related concern raised was that U.S. operational agencies have barely sufficient computing resources to perform their operational tasks, leaving inadequate resources for research using the operational models. This shortcoming must be addressed before broader collaborations between operational and academic scientists can become practical in using the operational models. Another suggestion for possibly bridging the weather and climate forecast time scales was to experiment using high-resolution weather prediction models to predict climate. Questions like how much resolution is needed for seasonal forecasting and for probabilistic prediction of high-impact weather are problems that can be tackled jointly with the climate community.

One of the focus areas of THORPEX was socioeconomic research and applications (SERA). It was remarked that prior to THORPEX, societal impacts of weather was a relatively neglected area. THORPEX helped jump-start research in this area. Currently, this field is much more active than it was 10 years ago, with agencies funding programs for multidisciplinary research involving physical and social sciences and engineering with consideration of the societal impact of natural processes and the associated hazards [e.g., Interdisciplinary Research in Hazards and Disasters Science, Engineering, and Education for Sustainability (Hazards SEES) and Coastal Science, Engineering, and Education for Sustainability (Coastal SEES) of NSF]. Speakers at the town hall argued that the new project should not stop at improving the prediction of high-impact weather but should aim at developing methods to predict the societal and economic impacts of weather as well.

The recent high-impact weather events over the United States, such as the tornado outbreaks in 2011 and Hurricane Sandy in 2012, clearly demonstrate the need for this type of research aimed at the prediction of high-impact weather and the assessment of the expected social, economic, and environmental impacts of such events. It was pointed out that impact forecasting requires adequately high spatial and temporal resolution, with a quantitative assessment of forecast uncertainties in the form of ensembles, as well as access to often only locally available information on vulnerability to weather events. In a few years' time, most modeling centers will be using models that will start to resolve convective scales. The skill of current weather forecast systems in predicting details crucial for the prediction of the impact of weather is lacking, so the need for related research is high.

Overall, the participants at the town hall endorsed the main ideas behind the proposed project. The funding agencies emphasized the need for innovative research related to forecasting significant weather events and their impacts. A suggestion at the meeting was to keep the proposed project well focused. This can ensure that interested scientists can easily align their research with the community effort and that the project objectives can be successfully accomplished over the lifetime of the project with the limited resources available. Key participants took the input from the U.S. THORPEX town hall meeting to the international planning workshop in Karlsruhe, Germany, for scientists from various countries to further refine the scope and objectives of the proposed project.