Linking Historical Tornado Trends to Today's Society through Climate Decision Support Services

The Palm Sunday tornado outbreak of 1965 and the Super Tornado outbreak of 1974 are arguably two of the most devastating and historically significant tornado events to have occurred in the central part of the United States. Both outbreaks produced large numbers of strong and violent tornadoes (F2-F5) and both events impacted parts of northern Indiana, southwest lower Michigan and northwest Ohio which are now covered by the National Weather Service (NWS) Northern Indiana office (KIWX). Many older local residents remember these events vividly and compare current day tornado events to those rare but extreme outbreaks. This prompts questions from core partners and the general public about changes in local tornado trends, intensity, and whether outbreaks such as 1965 and 1974 will become more frequent. This focus on outbreaks creates challenges for Decision Support Services (DSS) messaging, while creating an opportunity to utilize a new realm of NWS expertise: Climate Decision Support Services. In keeping with this year’s theme, we will look back at the historical frequency and intensity of tornadoes across the KIWX forecast area dating back to 1950. We will show that the number of strong and violent tornadoes across the KIWX area are decreasing due to the loss of these historical outbreaks in the averaging. The number of weak tornadoes (EF0 and EF1) show an increasing trend, which is leading to an overall increase in average annual tornadoes. We will discuss some reasons behind these trends and the perceptions of local residents as shaped by the rare historical tornado outbreaks. Lastly, we will offer some DSS messaging strategies in an effort to link this historical knowledge and statistical trends to today’s society in an effort to disprove common tornado myths, improve safety preparedness, and become a Weather Ready Nation.