- Due to the ongoing La Niña, severe weather conditions and tornadoes could suddenly kick in and rival one of the most notorious extreme weather seasons of all time (2011).
- Overall, tornado activity is expected to be slightly above normal for the year.
- Based on the past decades, the risk of tornadoes generally increases from February to March in the south.
Experts say this year’s tornado season could be more severe than usual in the United States, in part thanks to the ongoing La Niña.
The La Niña climate model – a natural cycle marked by cooler-than-average seawater in the central Pacific Ocean – is one of the primary weather factors in the United States and around the world, especially in late fall, winter and early spring. .
(El Niño is the warming of those same waters, causing different effects on weather conditions, according to Weather.com.)
AccuWeather meteorologists say that due to the pursuit of La Niña, inclement weather and tornadoes could suddenly kick in and rival 2011, one of the most notorious extreme weather seasons of all time, a year in the past. of which more than 550 Americans have been killed by tornadoes.
“The water temperature in the central and eastern tropical Pacific in February 2021 is similar to that of La Niña in February 2011,” said AccuWeather meteorologist Paul Pastelok.
A 2015 study found that a strong enough La Niña results in more tornadoes and hailstorms over parts of Oklahoma, Texas, Kansas, and other parts of the southern United States.
According to this study, La Niña concentrates warm, humid air over the southern United States, the National Oceanic and Atmospheric Administration said. The heat and humidity in the southern plains states create a strong north-south temperature gradient, which in turn promotes the formation of storms.
Another study from 2017 also found a link between tornado activity in the United States and the La Niña climate model.
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When is tornado season?
Based on the past decades, the risk of tornadoes typically increases from February to March in the south, and is highest from April to June in the plains, Weather.com said.
As for where tornadoes are most likely to strike, Pastelok said the central and lower Mississippi Valley and areas of the mid-Atlantic would present the greatest risk of severe weather this spring.
While several private forecast teams offer seasonal tornado forecasts, including AccuWeather and Weather.com, the federal government’s NOAA does not, at least not yet.
“Seasonal tornado forecasting is difficult and work is underway on the problem,” Harold Brooks, principal investigator at NOAA’s National Severe Storms Laboratory, told USA TODAY.
“A great value of seasonal forecasts is that they provide a place to highlight preparedness and safety information to the public. This is what matters most in hurricane forecasts and this is one reason why we might consider doing them (tornado forecasts) in NOAA, “he said. .
Overall, tornado activity is expected to be slightly above normal for the year, with the number of tornadoes expected to reach 1,350 to 1,500 in 2021 in the United States, according to AccuWeather meteorologists. Each year, the number of tornadoes averages between 1,250 and 1,400, according to US government statistics.
Last year was a below-average year for tornadoes across the U.S. According to preliminary figures, 1,075 tornado reports were reported in 2020, AccuWeather said.
Additionally, the number and severity of tornadoes in the United States in any given year do not appear to be related to human-caused climate change. In fact, a 2016 report from the National Academy of Sciences, Engineering and Medicine found that of all weather phenomena, severe storms and tornadoes are the most difficult to attribute directly to climate change.
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