La Niña could overload this year’s tornado season, just as it fatally affected in 2011

La Niña could overload this year’s tornado season, just as it fatally affected in 2011

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The past few months have been the strongest La Niña signal since the winter of 2010-2011. The question, then, is whether this spring still reflects the year, which ended up being the most expensive recorded for tornadoes and the deadliest in nearly 100 years.

“Heavy weather season is actually a collection of several short weather events, and anticipating individual events over long delivery times is usually tricky,” Sam Lillo, an atmospheric researcher at the University of Colorado Boulder, told CNN.

“What we can rather say is whether the probability that the ingredients for these events will come together is higher or lower than normal: this year it is higher than normal.”

The deadliest tornado season in modern history

The remarkable tornado season of 2011 was the deadliest in modern times, with more than 550 deaths – only second in 1925’s total of 794 tornado deaths.

Almost all of the deaths in 2011 occurred during the extremely active months of April and May. In April alone, there were 875 confirmed tornadoes, more than any month on record. The April 27 super outbreak recorded 226 tornadoes, the most tornadoes ever observed in a single day, including devastating turns in Birmingham and Tuscaloosa, Alabama.
Volunteers search destroyed homes on April 30, 2011 in Tuscaloosa, Alabama.
Just a few weeks later, Joplin, Missouri, was hit by an EF5 tornado on the scale that killed more than 160 people. It was the deadliest tornado in more than 60 years, as well as the most expensive tornado on record, with nearly $ 3 billion in direct damages.

“Looking back at 2011, it was the magnitude of the number of incidents, the fact that so many populated areas were hit and of course the incredibly high toll in terms of deaths, injuries and dollar damage,” said Bill Bunting, head of forecasting operations for the National Weather Service’s Storm Forecasting Center (SPCA).

Although localized and small-scale weather features played a role in setting up both of these tragic days, the overall large-scale weather patterns conducted in the historic 2011 tornado season are worth looking at to reduce the risk of similar days this year. determined.

“Every year has a bit of potential (from tornado outbreaks); it’s just trying to accurately predict, with as much delivery time as possible, where the area is likely to be and then making sure people are prepared and a plan, “Bunting said.

A person investigates damage one day after a tornado ripped through Joplin, Missouri, killing dozens of people on May 23, 2011.

Active forecast for this spring

To paint a picture of what the coming weeks to months might look like, forecasters are looking at La Niña and other global climate and weather patterns, such as the Arctic oscillation (which is different from the polar vortex), to create what is under- called seasonal forecasts.
Lillo manages one of these models that ‘focuses on the slow, predictable parts of the atmosphere’ to make predictions a few weeks in advance. Forecast models like this are important for things like seasonal forecasts of temperatures used in the energy trading market and hurricane season forecasts released each year by the National Oceanic and Atmospheric Administration (NOAA).

Lillo’s model recently predicted – with a month’s delivery time – the Arctic outbreak that gripped the central US in February. Now the focus is shifting to what these long-term patterns could reveal as we enter the spring-severe storm season.

“Overall, the forecasts show maturation with above-normal temperatures in the South, cooler in the north, and the temperature gradient that improves the jet stream in the middle of the US,” Lillo said. (The jet stream is the main storm orbit over the middle latitudes of the Northern Hemisphere and divides colder air in the north and warmer air in the south.)

During La Niña, stronger temperature differences develop between hot and humid air in the southern United States and cooler, drier air in the north. This results in a faster jet stream that can cause severe weather outbreaks.

“The faster jet stream has all the potential for stronger storm systems and severe weather,” Lillo said.

In March, southern America is historically the area where severe storms, including tornadoes, are more likely. As the Northern Hemisphere begins to warm up, the bull’s eye for tornadoes will move westward to the central US and eventually northward to the northern plains, it’s summer.

“The jet stream pattern is not unfavorable for heavy weather because we are coming later in March and definitely after that,” Bunting said. “If the pattern holds, very strong wind fields across the Gulf Coast in the vicinity of warm, humid air indicate that the Gulf Coast could be an area to keep a close eye on in the short term.”

How La Niña relates to tornadoes

Similar to this year, a moderate La Niña was the most important feature in 2011. La Niña, and its counterpart, El Niño, may play an important role in the position of the jet stream, temperature and precipitation patterns in the USA, which all plays a role in the formation of severe weather.

The El Niño or La Niña conditions in the winter months can be used to determine the tornado frequency during the peak of the severe storm season in the spring, recent studies have found.

“The flow of hot, humid air from the Gulf of Mexico increases during springs following La Niña, producing the fuel needed to form storms,” ​​said Jason Furtado, assistant professor of meteorology at the University of Oklahoma. , said.

“The stronger flow increases the low level shear that also benefits the formation of tornadoes and hailstorms.”

The past few months have marked the strongest La Niña since 2011, and the pattern is expected to have an impact on the weather over the next few months, according to the NOAA’s Climate Forecast Center.

The time to prepare is now

While severe storms occur throughout the year throughout the U.S., the peak time for severe storms is during the meteorological spring, which includes March, April and May.

So far this year, there have been only 27 tornado reports, which is far below normal. Over the past 15 years, the U.S. has had an average of about 130 tornado reports during the first few days of March.

But it’s not just tornado reports that are down. Greetings and damaging wind reports are below average so far this year.

“There were a lot of seasons that started quietly and did just the opposite,” Bunting said.

2011, according to data compiled by the SPCA, also started below average for both tornado and hail reports, before accelerating rapidly into the rest of the spring.

The upcoming forecast is based on where the jet stream will end up in the coming weeks.

Now is the time to review your plans for severe weather. Know where to find your daily local forecast. You can find several ways to get serious storm and tornado watches and alerts: via Wireless Emergency Alerts, NOAA Weather Radio, local news stations and more. And know where you are hiding at home, work or school if there is a tornado.

Advised Bunting: “This is the time of year where we need to think a little more about the potential for severe storms and develop pre-event planning.”

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