The Van Trump Report

Could La Niña Trigger Severe Weather this Spring?

Many farmers around the country are still cleaning up the mess that winter recently doled out, but attentions are already turning to what spring weather might have in store. Winter doesn’t officially end until the Spring equinox on March 20 but there are several items on the wish list already, as well as worries that some of the severe weather that spring can bring with it might be exacerbated by the La Niña phenomenon.

According to the most recent update from the National Oceanic and Atmospheric Administration’s Climate Prediction Center (NCEP), La Niña is present. For those not familiar, La Niña is the periodic cooling of waters in the eastern equatorial Pacific that is known to change seasonal weather patterns throughout the world. El Niño is the warming of these same waters, which leads to different effects on weather patterns. ENSO says chances are greater than 60% that the weather phenomenon will be present throughout early spring but estimate a 60% chance that neutral conditions will return during the April-June 2021 period. By the fall, the chance that La Niña will return is approximately equal to the chance that it will not.

La Niña’s impact could include increased tornadoes and other severe weather activity in early spring this year, according to meteorologists. Obviously, severe weather outbreaks can happen any time of year, but peak spring storm activity typically occurs in the months of March, April, and May. As Accuweather explained in its spring forecast preview, tornado season got off to an early start in 2019 and 2020. This year, forecasters say weather conditions resemble those witnessed during the La Niña pattern in February 2011, which resulted in one of the most active springs in recorded history. But it got off to a late start, with below-average activity during February and March. That April, however, saw over 700 tornadoes. This has meteorologists speculating that this year’s severe spring weather period could be late to arrive as well.

As of Feb.16, the Storm Prediction Center (SPC) reports that 23 tornadoes had touched down so far in 2021. On average, 64 tornadoes occur during January and February in the U.S. Tornado activity is forecast to be slightly above but near normal for the entirety of the year with the number of tornadoes expected to reach 1,350-1,500 in 2021 across the United States, according to AccuWeather long-range meteorologists. Annually, the number of tornadoes averages between 1,250 and 1,400, according to U.S. government statistics. Last year’s tornado activity was below normal, with only 1,075 reports, although the storms were more deadly. In 2020, 76 fatalities were blamed on tornadoes, nearly double the three-year average.

AccuWeather’s long-range forecast predicts 275 to 350 tornadoes during April 2021 alone, with the mid- to lower Mississippi Valley and the mid-Atlantic at the highest risk for severe spring weather. AccuWeather Lead Long-Range Meteorologist Paul Pastelok warns that increased severe weather could be particularly dangerous for these regions, especially for the mid-Atlantic, which usually gets only a small percentage of tornado activity each year.

At the same time, the region extending from South Dakota to northern Texas, aka “Tornado Alley,” could see below-average severe weather activity. Research has found that the energy that allows for the lift needed for a thunderstorm’s updraft growth in La Niña is focused more in the Southeast – in so-called Dixie Alley – during March, and in the Plains states along Tornado Alley in April. Forecasters say Dixie Alley, which includes the Mississippi and Tennessee valleys, could see a heightened chance of severe thunderstorms during late March and April. Some of these areas were also pummeled during the 2011 season, which is drawing some comparisons from meteorologists. April 2011 featured the infamous Super Outbreak with more than 360 tornadoes touching down over a three-day period across 20 states. Most of the activity during that outbreak occurred in the Deep South, according to AccuWeather.

Pastelok says there are some key factors that could keep this spring from being as active as 2011, though. One of those is the drought over the Four Corners (the southwestern corner of Colorado, southeastern corner of Utah, northeastern corner of Arizona, and northwestern corner of New Mexico) and into part of the High Plains, including eastern Colorado, western Kansas, western Nebraska and part of the Texas Panhandle. Additionally, extreme drought conditions that began developing in 2020 across the Four Corners region threaten to expand this spring across the central and southern Plains. These areas of dryness will inhibit some of the thunderstorm development and are one reason AccuWeather is predicting the focus of tornado activity to occur over an area farther east than the traditional Tornado Alley. (Sources: Accuweather, The Weather Company, NOAA)

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