Lives Saved vs Time Lost: Direct Societal Benefits of Probabilistic Tornado Warnings

National Weather Service is planning to implement the system of probabilistic tornado warnings. In this paper, we estimate and compare full societal costs of tornadoes with existing deterministic and potential probabilistic warnings. These full costs include the value of statistical lives lost as well as the value of the time spent sheltering. We find that probabilistic tornado warnings would decrease total expected fatalities. The improvement in decision-making would also decrease the total opportunity cost of time spent sheltering even though the total sheltering time is likely to increase. In total, probabilistic warnings should lower societal costs of tornadoes relative to deterministic warnings by approximately $76-139 million per year with a large portion of this improvement coming from lower casualties.