When most Americans talk about El Niño and its relationship to US weather, they talk about how it affects temperatures, snowfall, rainfall, or even hurricanes.
Few talk about how El Niño, which warms the waters of the eastern Pacific, affects tornadoes.
That makes sense, in a way. Until recently, experts shied away from tying these periodic events to tornado activity.
Evidence is mounting, though, that El Niño’s presence impacts how many tornadoes pop up in a season. In particular, it makes it less likely one will hit a Tornado Alley state. And it makes it more likely one will hit California or Florida.
It’s All About the Jet Stream
How does El Niño influence whether or not twisters form in one part of the US or another?
It “helps set the stage by creating a stronger and more southerly jet stream," Robert Molleda, a forecaster at Miami’s National Weather Service, told Florida’s Sun-Sentinel in February.
Adds Michael Ventrice, a meteorologist for The Weather Company: “during strong El Niño states, we see an enhancement to the sub-tropical jet stream in response to persistent convection that percolates over the central and eastern Pacific.” Specifically, the sub-tropical jet stream provides energy and moisture to “developing storm systems that then push across the southern tier of the US.”
To put it another way, Geoff Linsley, an associate meteorologist at West Coast Weather, says the jostled jet stream pushes the “major track of tornados … further South than normal.”
Florida’s El Niño-Enhanced Twisters
That change is on full display in the Sunshine State right now—or so it seems.
According to the Sun-Sentinel, for instance, five twisters slammed South Florida in just three weeks earlier this year. Typically, it sees eight in an entire tornado season.
Unfortunately, forecasters say more may be on the way. "The prospects for this to occur again are relatively good,” Greg Carbin, a meteorologist at the Storm Prediction Center, told the newspaper last month.
As for California, it’s currently unclear if the state’s seeing more or fewer twisters than usual. Still, it was the site of the US’ first confirmed tornado of 2016. (The EF-0 funnel touched down near Hollister on Jan. 6.)
Other States Affected Too
Curiously, many other parts of the country also have seen a lot of tornado activity so far this year.
In fact, tornadoes and straight-line winds damaged property from the Plains all the way to the East Coast in February. Also, those same storm systems produced the greatest number of February tornadoes in the US since 2008.
At least 13 of them hit Louisiana and seven hit Mississippi on a Feb. 23 alone. And two days later Virginia saw its strongest and deadliest February twister on record.
Is El Niño Truly Responsible?
Can we really blame the lingering El Niño for all of these twisters? Maybe not directly, but it surely had a hand in whipping up the many funnel clouds that have wreaked havoc so far in 2016.
Whether or not it’ll whip up even more of them in the coming months is another question. After all, one prominent forecast suggests this spring will be a quiet one overall as far as tornadoes are concerned.
That forecast says there’s a 54 percent chance the US will see a below-normal number of twisters between March and June.
Compare those odds to the ones in an average year—when the likelihood of a below-normal number of tornadoes is 33 percent—and it’s easy to see how El Niño can throw a wrench into the works.
All it Takes is a Single Tornado…
Even if that prediction comes true, experts warn people living in areas that could see fewer twisters this season against thinking they don’t have to worry.
Why? “There are times when the atmosphere can move into states that oppose the base state, such as El Niño,” Ventrice says. Although “we may have a general way of thinking about the pattern, there are weeks within the seasonal pattern that may not align with the conceptual model we [have] about a particular season.”
For example, he shares that sometimes “weather across the US [will] look more like a La Niña pattern even though the Pacific is in a strong El Niño state.” In other words, a tornado outbreak still could strike an area that’s supposed to see fewer twisters during an El Niño year.
Ventrice compares the situation to the one that pops up every hurricane season. “Even though we may predict a below-normal hurricane season, [it] does not mean the US will not experience a land-falling hurricane.”