a violent Tornado String It swept across the United States last week, killing dozens of people and leaving a trail of destruction in its wake.
Homes and buildings were reduced to rubble as the twisters tore across a wide swath of the South, Midwest and parts of the Northeast. There were reports of people trapped under the rubble of destroyed homes in Alabama and Arkansas, while residents of a town west of Memphis said they woke up Sunday morning to find the local high school building in ruins. In Illinois, one person died and several others were injured after a storm system hit the area Friday night For a packed theater roof to collapse.
At least 33 people were killed in tornadoes that struck last weekend alone At least five others died Wednesday in southeast Missouri after a tornado touched down just before dawn, officials said.
A spokesman for the National Oceanic and Atmospheric Administration confirmed to CBS News Wednesday afternoon that the latest series of deadly storms brought the overall number of tornado-related deaths this year to at least 63. That number accounts for all tornado-related deaths recorded nationwide since the beginning of 2023, and it’s already pretty close to the average number of U.S. deaths recorded in a 12-month period.
“It’s been unusually busy with tornadoes since the beginning of the year,” The Weather Channel meteorologist Jackie Geras told CBS News on Thursday, citing a fairly persistent upper-level weather pattern that’s conducive to severe storms. Gerras suggests that La Niña, a set of climate conditions that refers to how cooling temperatures in the Pacific Ocean alter global weather patterns.
“Our busiest tornado seasons are usually during La Nina,” he said.
Based on 30 years of data collected between 1993 and 2022, the average annual number of deaths linked to tornadoes in the United States is 71, according to the National Weather Service. The agency’s Storm Prediction Center reported the highest incidence of fatal twisters in Alabama, Missouri, Tennessee, Oklahoma and Georgia, with average deaths of 14, eight, seven, five and five, respectively. Arkansas, Kentucky, Mississippi and Texas follow closely behind with an average of four deaths per year.
Several of these states already have confirmed tornado-related deaths near their annual average. Even in Delaware, which has recorded an average of zero annual deaths associated with tornadoes, a Suspect Twister At least one person was killed when a structure collapsed near the town of Greenwood on Saturday night, local authorities said at the time.
“The death toll has gone up for a couple of reasons,” Xerras explained. “Obviously, the more tornadoes you have, the higher the risk of death. But, the stronger the tornado, the higher the death toll. We’ve also had a lot of nighttime or nocturnal tornadoes, which are twice as likely to happen. Deadly.”
A big leap this year
The National Weather Service keeps track of particularly devastating storms — which the agency classifies as “killer tornadoes” — as they occur across the country each year. Weather service data shows that it’s relatively uncommon for storms of this magnitude to occur in clusters, though it’s not unheard of. In April 2020, for example, the agency recorded 13 “killer tornadoes” in the space of a month.
Depending on the region, “tornado season” usually peaks in late spring or summer, although scientists say that, under the right conditions, tornadoes can occur at any time anywhere in the United States. are the most frequent, and April “begins the most dangerous three-month period for tornadoes.”
During the spring season, the greater contrast between the air masses and the sinking of the jet stream “produces the combination of cool, dry air with warm, moist air from the Gulf of Mexico,” he told CBS News. These atmospheric conditions can create tornadoes that are stronger, longer lasting, and more destructive.
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The high death toll reported this year comes alongside an unusually high incidence of tornadoes, according to National Weather Service records. Between Jan. 1 and April 5, 2023, the agency has confirmed at least 367 tornadoes, Matthew Elliott, warning coordination meteorologist for the agency’s Storm Prediction Center, said in an email to CBS News Wednesday afternoon.
That preliminary number differs slightly from the one displayed on the Storm Prediction Center’s website, which reflects the 422 eyewitness reports of tornadoes the weather service received from the top of the year through Monday. The initial total is often an overestimate, “because the same tornado can be reported multiple times,” especially when a tornado has a long track, Elliott said. After submitting the report, officials conduct ground surveys to determine if a tornado actually occurred.
The 367 tornadoes confirmed by the survey through Wednesday, in more than 25 states, marked a huge jump from the number of storms typically recorded during this time in a given year. Based on weather service data that has tracked actual tornadoes in any state between January and early April in the past four years, the number represents at least a 53% increase in tornadoes over the four-year average, which is about 239 storms.
A closer look at the data shows that some years were more severe than others, with officials recording 502 tornadoes nationwide through the end of April 2022. A year ago, the National Weather Service confirmed just 243 tornadoes during the same period, although the cumulative highs recorded in late April 2020 and 2019 were similar to last year.
Impact of climate change
Despite some variability from year to year, the brutal tornadoes that have wreaked havoc since late March have fueled Repeated questions On a possible relationship between climate change and the frequency, intensity, and location of tornadoes in the United States
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“I think that climate change may play a role in the intensity and frequency of tornadoes,” Geras said, noting how “in recent years we’re seeing areas where tornadoes occur more often” and “tornado alley” — a stretch of the U.S. that’s commonly associated with twisters. Remains — “Adjustments may be necessary.”
Officials caution against deciphering any patterns Tornado activity Complicated because official records only go back seven decades and the weather service doesn’t release its final monthly event numbers until 75 days after the end of each month. But, while scientists can’t say for sure that a causal link exists between warming and tornado activity, they do acknowledge that climate change could affect and possibly exacerbate the atmospheric conditions necessary for tornadoes to occur.
NOAA scientists said human-caused climate change may play a role in “shifts in tornado activity” in a 2019 report assessing their relationship. The report notes that tornado activity depends mainly on “the strength of atmospheric turbulence” and “vertical wind shear, which provides the necessary rotation for tornadic thunderstorms.” Temperature variations linked to climate change affect both of these things, scientists say.
“While early indications suggested a potential tug-of-war between these two processes, recent studies have shown an overall increase in the expected number of days where sufficient instability and wind shear occur simultaneously,” they wrote in the report.
A recent study published by the Bulletin of the American Meteorological Society in January found that a warming climate could contribute to more frequent supercell thunderstorms in the future, which may occur outside of the traditional storm season. Because intense supercell storms can cause a variety of severe weather events, including tornadoes, the study’s authors said the findings “suggest the potential for more significant tornadoes, hail, and extreme precipitation that, combined with an increasingly vulnerable society, could have catastrophic consequences.”