	Overview

Severe thunderstorms and tornadoes affect communities across the United States every year, causing fatalities, destroying property and crops, and disrupting businesses. According to the National Science and Technology Council: "Due to changes in population demographics and more complex weather-sensitive infrastructure, Americans today are more vulnerable than ever to severe weather events caused by tornadoes, hurricanes, severe storms, heat waves, and winter weather." However, on May 20, 2013, the town of Moore, Oklahoma, was struck by a large and extremely destructive tornado (ranked EF-5, the most destructive on a scale of 0-5; EF rankings, or intensity scale, for tornadoes are discussed in Appendix ). 1786 ). Congress attempted to clarify the federal role in mitigating damages from windstorms (including tornadoes and thunderstorms) by passing the National Windstorm Impact Reduction Act of 2004 ( P.L. 108-360 ). It is not clear whether the program made progress toward its objective: achievement of major measurable reductions in the losses of life and property from windstorms. In addition, the four agencies responsible for implementing the program—the National Science Foundation (NSF), the National Institute of Standards and Technology (NIST), NOAA, and the Federal Emergency Management Agency (FEMA)—have not identified a line item for the program in their annual budget justifications. The bill states that the purpose of the program is 
to achieve major measurable reductions in the losses of life and property from windstorms through a coordinated Federal effort, in cooperation with other levels of government, academia, and the private sector, aimed at improving the understanding of windstorms and their impacts and developing and encouraging the implementation of cost-effective mitigation measures to reduce those impacts. In the 111 th Congress, the House passed similar legislation, H.R. As of May 22, 2013, similar legislation has not been introduced in the House or Senate. However, the evidence is unclear as to whether the frequency and intensity of severe thunderstorms and tornadoes has increased or will increase in the future due to climate change. The 2011 Tornados: A Link to Climate Change? Forecasting and Warning: The Role of the National Weather Service

The NWS, at the discretion of the Secretary of Commerce, has statutory authority for weather forecasting and for issuing storm warnings (15 U.S.C. Thus it is not clear whether long-term efforts to mitigate greenhouse gas-induced global warming—such as by reducing emissions of carbon dioxide and other gases—could also mitigate damage to property and reduce injuries and losses of life from severe thunderstorms and tornadoes. The role of the federal government in weather and climate research, thunderstorm and tornado forecasting, and issuing warnings is substantial. They are the destructive products of severe thunderstorms, and second only to flash flooding as the cause for convective storm related fatalities. Risks from Tornadoes
Damages from violent tornadoes seem to be increasing, similar to the trend for other natural hazards. According to some insurance industry analysts, losses of $1 billion or more from single tornado events are becoming more frequent. The results would suggest that there are limits to the number of potential lives saved by improvements in forecasting ability and warning systems, and that social, behavioral, and demographic factors may play an increasingly important role in tornado-related fatalities.
Severe thunderstorms and tornadoes affect communities across the United States every year, causing fatalities, destroying property and crops, and disrupting businesses. Tornadoes are the most destructive products of severe thunderstorms, and second only to flash flooding as the cause for most thunderstorm-related fatalities. Damages from violent tornadoes seem to be increasing, similar to the trend for other natural hazards—in part due to changing population, demographics, and more weather-sensitive infrastructure—and some analysts indicate that losses of $1 billion or more from single tornado events are becoming more frequent.
Policies that could reduce U.S. vulnerability to severe thunderstorms and tornadoes include improvements in the capability to accurately detect storms and to effectively warn those in harm's way. The National Weather Service (NWS) has the statutory authority to forecast weather and issue warnings. Some researchers suggest that there are limits to the effectiveness of improvements in forecasting ability and warning systems for reducing losses and saving lives from severe weather. The research suggests that, for example, social, behavioral, and demographic factors now play an increasingly important role in tornado-related fatalities.
One issue for Congress is its role in mitigating damages, injuries, and fatalities from severe thunderstorms and tornadoes. The National Science and Technology Council has recommended the implementation of hazard mitigation strategies and technologies, including some—such as conducting weather-related research and development and disseminating results—that Congress has supported through annual appropriations for the National Oceanic and Atmospheric Administration, the National Science Foundation, the Federal Emergency Management Agency, the National Aeronautics and Space Administration, and other federal agencies. Other recommended strategies include land use and zoning changes, which are typically not in the purview of Congress.
Congress attempted to clarify the federal role in mitigating damages from windstorms (including tornadoes and thunderstorms) by passing the National Windstorm Impact Reduction Act of 2004 (P.L. 108-360). It is not evident whether the program made progress toward its objective: achievement of major measurable reductions in the losses of life and property from windstorms. Authorization for the program expired at the end of FY2008. In the 113th Congress, legislation introduced in the House (H.R. 1786) would reauthorize the wind hazards program through FY2016. Similar legislation was introduced in the House and Senate in the 112th Congress, but no action was taken.
It is not clear whether changes to climate over the past half-century have increased the frequency or intensity of thunderstorms and tornadoes, or whether climate changes were responsible for the intense and destructive tornado activity in 2011, or for the extremely destructive EF-5 tornado that struck Moore, Oklahoma, on May 20, 2013. An issue for Congress is whether future climate change linked to increases in greenhouse gas emissions will lead to more frequent and more intense thunderstorms and tornadoes, and whether efforts by Congress to mitigate long-term climate change will reduce potential future losses from thunderstorms and tornadoes.