2012 Tornadoes: Questions and Answers

Coming on the heels of one of most active and deadly tornado years in U.S. history, tornado events began even earlier in 2012, by comparison. After an unusual pre-dawn EF4 tornado killed 7 in Harrisburg, Illinois on Leap Day, February 29, a significant killer tornado outbreak raked areas of the Ohio River Valley, and claimed at least 40 lives, only two days later, on March 2. Questions about the earlier start and intensity of the tornado activity were pondered by the public and media; Does global warming play a role in tornado intensity? Did the well-above normal winter temperatures portend an earlier and more active severe weather “season”? Because of the very early start to tornadoes in 2012, will the year be similar to 2011? Does a fading La Niña affect severe weather? How often does the Storm Prediction Center issue a High Risk in the month of March?

We will look into these interesting questions and provide answers for some of them, in addition to reviewing other tornado events occurring in 2012. The relatively short official U.S. tornado record (NOAA/NWS data back to the early 1950s) will be used to assess the tornado year mid-point over the last 60 years with an eye toward revealing trends that could indicate an earlier mid-point has been occurring in recent years. We will also examine the annual trends in reported tornado intensity, and whether there is a correlation between a warm winter season and subsequent springtime tornado activity. Lastly, we will briefly address the challenges involved in producing seasonal tornado forecasts due to the great variability experienced across the U.S. in annual tornado activity levels and the poorly understood temporal and spatial scale interactions involved.