The 2021 tornado season may be more destructive because of La Niña. Here's the forecast.

Doyle Rice, USA TODAY
·3 min read

This year's tornado season could be more severe than usual across the USA, in part because of La Niña.

The climate pattern called La Niña – a natural cycle marked by cooler-than-average ocean water in the central Pacific Ocean – is one of the main drivers of weather around the world, especially during the late fall, winter and early spring.

El Niño is the warming of these waters, which leads to different effects on weather patterns, according to Weather.com.

AccuWeather meteorologists said that because of La Niña, severe weather and tornado activity could abruptly fire up and rival 2011, one of the most notorious severe weather seasons, when tornadoes killed more than 550 Americans.

"The temperature of the water in the central and eastern tropical Pacific during February 2021 is similar to the La Niña pattern in February 2011," AccuWeather meteorologist Paul Pastelok said.

A study in 2015 from Columbia University found that a fairly strong La Niña brings more tornadoes and hailstorms over portions of Oklahoma, Texas, Kansas and other parts of the southern USA.

La Niña concentrates hot, humid air over the southern USA, the National Oceanic and Atmospheric Administration said. The heat and humidity over the southern Plains states sets up a strong north-south temperature gradient, which in turn favors storm formation.

A study in 2017 published by the American Meteorological Society also found a link between U.S. tornado activity and La Niña.

'Truly, truly a disaster': 3 dead, at least 50 homes damaged as tornado rips through North Carolina

Based on past decades, the chance for tornadoes typically increases from February into March in the South, and it is highest from April through June across the Plains, Weather.com said.

Pastelok said the mid- to lower-Mississippi Valley and the mid-Atlantic regions will have the highest risk for severe weather this spring.

Though several private teams offer seasonal tornado forecasts, including AccuWeather and Weather.com, the federal government's NOAA does not, at least yet.

"Seasonal tornado forecasts are challenging, and there's some work being done on the problem," Harold Brooks, a senior research scientist at NOAA's National Severe Storms Laboratory, told USA TODAY.

"A big value of seasonal forecasts is that it provides a venue to highlight preparation and safety information to the public. That's the biggest thing about the hurricane forecasts and is a reason we might consider making them (tornado forecasts) in NOAA," he said.

Tornado activity is forecast to be slightly above normal for the year, and the number of tornadoes is expected to reach 1,350 to 1,500 in 2021 across the USA, according to AccuWeather meteorologists. Annually, the number of tornadoes averages 1,250 to 1,400, according to U.S. government statistics.

Already this year, there have been two deadly tornadoes, according to the Storm Prediction Center: one in central Alabama on Jan. 25, which killed one person and injured at least 30, and another in North Carolina on Feb. 15, in which three people died. The North Carolina twister, which left at least 10 people injured, hit southeastern Brunswick County near Grissettown.

Last year was a below-average year for tornadoes. According to preliminary figures, there were 1,075 reports in 2020, AccuWeather said.

The number and severity of tornadoes in any given year do not appear to be linked to human-caused climate change. A report in 2016 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.

Record cold, intense storms and tornadoes amid global warming: Could there be a connection?

This article originally appeared on USA TODAY: Tornado season forecast: La Niña may fuel more tornadoes in 2021