Climate Matters: Change in nocturnal tornadoes driven by more than climate

Severe storms account for a large portion of the most expensive disasters but linking events of small-scale storms to the broad concept of climate change can be difficult. Half of all billion-dollar disasters in the United States are due to severe storms and these events are on the increase.

Research has not identified a definitive link between the number of severe storms and tornadoes and a changing climate, but there are some factors we can forecast. The number of days favorable for tornadoes is expected to increase across the Eastern U.S. into the later century. And these areas are where communities are the most vulnerable to severe storms.

While we can't say for certain how the climate has affected tornadoes over recent decades, human behavior and vulnerability have changed in that time. The proportion of tornado fatalities during the daytime has decreased over the last 140 years by 20% while those at nighttime have increased 20%. This trend is attributed to advances in forecasting and warning during the day, while more communities remain vulnerable overnight.

This is where researchers are becoming more concerned about impacts on people; while the climatological threat from nocturnal tornadoes may increase, the risk of these overnight storms is also rising. Socioeconomic risk plays a large role and the most vulnerable are expected to see an increased risk of tornadic days.

Severe storms and tornadoes are already concentrated across the Plains, the Mississippi Valley, Mid-South, the Tennessee Valley, and the Deep South. Large numbers of the population in these regions live in mobile and manufactured housing; nocturnal tornadoes can be 2X as deadly as their daytime counterparts and 10X as deadly for mobile homes.

Vulnerability in mobile homes is a deeply complex issue that will require widespread effort to unravel. One problem identified by new research is in the anchoring of these homes. There are standards for how secure manufactured homes must be but these requirements are lower for inland areas than the coast due to hurricane risks. However, tornadoes still affect a wider area, and good practice when buying a mobile home is to secure it as if that house were on the coast to ensure the best anchoring.

For nocturnal tornadoes, it is imperative to have multiple ways to receive weather alerts. Many fatalities at night are due to unaware victims who are asleep, and many people silence their phones at bedtime. A NOAA weather radio is an easy solution when other ways of getting information fail, and these radios can be turned loud enough to wake you in time to get to safety before the storm.