Definition of ‘extreme’ weather in Texas is unsettled
Texans know many types of severe weather — thunderstorms, hailstorms, tornadoes, hurricanes, freezes and tropical storms — but when does severe weather turn extreme?
Although the National Weather Service does not have a formal definition of extreme weather, the word describes many types of weather events in daily forecasts and weather reports around the globe.
However, some researchers argue that, because climate change is increasing the frequency of extreme weather events, having a cohesive definition of what constitutes extreme weather will improve public understanding and help authorities manage those events. Others think defining “extreme” may not work because of the inherent subjectivity of the word.
“Depending on the context, what’s extreme will differ,” said Jen Henderson, assistant professor of geosciences at Texas Tech University. “There’s a certain amount of subjectivity when it comes to defining what an extreme event is.”
Financial angle
One way to define an extreme event would be to see if it was a billion-dollar weather event. Between 1980 and 2023, the nation was hit by 170 confirmed weather and climate events that each produced damage worth more than $1 billion, according to a recent National Oceanic and Atmospheric Administration report.
In 2023, Texas led the country in billion-dollar weather and climate disasters, with 16, which resulted in a total of more than $20 billion in shared losses, and the events are happening with more frequency, the NOAA report said.
Looking back
NOAA has another way to define an extreme event: It would be extreme if a time and place in which weather, climate or environmental conditions — such as temperature, precipitation, drought or flooding — rank above a threshold value near the upper or lower ends of the range of historical measurements.
Often, these atypical weather events that have not happened to a community or rarely occur are considered extreme. The February 2021 Texas freeze, in which the entire state was under a winter storm warning, had Texas experiencing weather conditions it wasn’t prepared for. In addition to widespread blackouts, infrastructure problems such as water outages and icy roads across the state halted normal public activity. Federal investigators attributed the blackouts to “extreme cold temperatures and freezing precipitation,” in their official report.
“Something like that probably won’t happen for another 100 years in Texas,” said Timothy Logan, assistant professor at Texas A&M’S School of Atmospheric Sciences.
The rarity of the event, along with the power outages that occurred during a pandemic, caused the storm to be considered a “triple extreme weather event,” according to research published in 2022 in the Journal of Extreme Events, a publication that navigates the inherent ambiguity of defining an extreme event.
Question of place
Some weather events produce conditions within the threshold of previous historical measurements but because the events happen in a place where more damage can occur, they also would be labeled as extreme.
Susan L. Cutter, in a 2014 paper for the University of South Carolina titled “What Makes Events Extreme,” addresses this issue by raising the question: “Are these events more extreme (climatologically or meteorologically), or are they just affecting more population areas with more infrastructure to damage, thus becoming an extreme event based on consequences?”
Cutter helped create the Journal of Extreme Events, which she said intends to promote understanding of “climate-related risks and hazards and policy alternatives for their reduction and management.”
Texas A&M’S Logan suggested that some areas are more prone to extreme weather events and that defining what constitutes extreme weather is complicated by where people decide to build roads and property. In his other role as the director of the Houston Lightning Mapping Array Network, Logan pays attention to the growth and development around the Houston area.
“I know the lightning hot spots, or where homes and roads are being built where it’s going to flood no matter what,” Logan said. “There are always going to be an extreme event in those areas.”
Texas Tech’s Henderson, a social scientist, studies more of the human toll of natural disasters rather than the physical consequences. Henderson said some communities are more prepared for or more resilient after extreme weather than others.
“Some communities have better infrastructure, they might have better housing or different things that contribute to them being able to survive whatever hazard is impacting them,” Henderson said.
Damage to society
The National Weather Service has started implementing impact-based warnings ahead of some severe weather events. The warnings account for the severity of the weather and the social damage that might be done.
“They’re trying to move more toward the way that society or communities will experience a particular hazard, but that is still to say, they’re not necessarily tracking and measuring the extremes for communities,” Henderson said.
A spokesperson for the weather service said that although it doesn’t have a definition for extreme weather, the agency will be unveiling an experimental Heatrisk tool in April that takes into consideration its forecasts and national Centers for Disease Control and Prevention heat health data to “place extreme heat into a climatological context and provide awareness to more sensitive groups.”
But if a weather forecast uses the word extreme, the weather service spokesperson said, “it’s relaying the range of possible impacts related with a weather hazard to allow decision-makers (such as emergency managers or city officials) to make smart and sound decisions related to the city and community.”