Monitoring and Understanding Trends in Extreme Storms

NCDC scientists and collaborators studied trends for severe convective storms, extreme precipitation, hurricanes and typhoons, and severe snowstorms and ice storms and evaluated the state of knowledge regarding our scientific understanding of the causes of the trends, or lack of trends, they found. The results of their efforts are being published in a paper entitled Monitoring and Understanding Trends in Extreme Storms: State of Knowledge in the Bulletin of the American Meteorological Society.

Key Findings:

  • The scientists established that collection of reports of severe convective storms like tornadoes, hailstorms, and severe thunderstorms has not been uniform over time because of changes in forecast verification and emphasis, which makes detecting trends in severe convective storms extremely difficult. Instead, the scientists looked for changes in the environmental conditions that are favorable for the development of severe thunderstorms but did not identify any clear trends.
  • Regarding extreme precipitation, the scientists found strong evidence of an increase in the frequency and intensity of these events. Although they have not been able to determine the exact causes of these observed trends, there is evidence that increasing atmospheric water vapor may be one factor.
  • For hurricanes and typhoons, scientists are significantly constrained in their ability to detect trends in Atlantic and western North Pacific tropical cyclone activity due to an assortment of data issues and an inability to quantify the natural variations in tropical cyclone activity. Attributing past tropical cyclones to human-induced climate change is also challenging due to a lack of consensus on the links between specific climate system characteristics and tropical cyclone activity.
  • For severe snowstorms and ice storms, the number of severe regional snowstorms that occurred since 1960 was more than twice that of the preceding 60 years. However, there have been no significant trends in the area of the United States impacted by extreme snowfall amounts since 1900. The scientists also found no distinguishable trend in the frequency of ice storms in the United States as a whole since 1950.