La Niña’s effect on deadly tornadoes in the spring
NASHVILLE, Tenn. (WKRN) — The climate patterns of “El Niño” and “La Niña” impact the weather in Middle Tennessee and Southern Kentucky in various ways. When the La Niña pattern is active, there have been signs it correlates to more tornadoes, some of those deadly in the spring season.
What is La Niña?
La Niña has to do with the waters in the Equatorial Pacific Ocean. When these waters are colder than normal, La Niña is in effect, impacting our weather in the United States. The La Niña pattern usually brings Middle Tennessee and Southern Kentucky warmer temperatures and greater Gulf moisture. If the pattern is strong, it can create a greater clash of warmer & colder air, possibly increasing the potential of major severe weather.
FORECAST: Middle Tennessee & Southern Kentucky Weather
The key here is the *possibly increasing* the risk of severe weather. Meteorologists determine the potential of big severe weather events based on the strength of La Niña.
Alyssa Clements, Meteorologist with the National Weather Service in Nashville says “There is a signal when you have a La Niña during the winter months and into the early spring, those are typically connected with more severe weather & tornadoes. It’s about the opportunity and not a guarantee. There has to be available Gulf moisture to keep temperatures warm, aided by a strong polar jet stream that brings the colder air.”
Past La Niña events leading to tornado outbreaks
Middle Tennessee has seen several deadly tornado outbreaks due to La Niña, with four of these events in the Spring severe season.
Here are two examples, showing the impact of La Niña by looking at the strength of the climate pattern during the prior seasons leading into the tornadic event.
The April 3-4, 1974 Super Outbreak. From the latter part of 1973 into 1974, the strength of La Niña was strong, contributing to a big clash in the airmasses to support a multi-state tornado outbreak.
Another example, just outside of the spring months, was the Super Tuesday tornado outbreak of February 5-6 2008 that killed 22 people in Tennessee. The period of December to February signaled a strong La Niña. However, looking farther back in the previous year of 2007, there were additional tornado events that occurred in the strong La Niña signal, all of this followed the extreme drought and heat wave in the summer months.
These two events give us understanding that in strong La Niña’s we can have more tornadic events. However, the climate pattern’s impact will always vary on the hyper-local weather analysis at the time of storm occurrence.
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