There has been lots of talk recently about our ongoing El Niño, even named the “Super” El Niño. But what does that even mean? I’m sure you’ve seen all sorts of predictions about what this may spell for this upcoming winter – I’ve heard it all from a ton of snow to tornado outbreaks. Here, we’ll just talk facts.
In this blog, we’ll try to answer three questions.
- What is El Niño?
- What makes this a “Super” El Niño?
- What does this mean for us here in Middle Tennessee?
What is El Niño?
To understand this, we must first look at what a teleconnection is.
According to climate.gov, “teleconnections are significant relationships or links between weather phenomena at widely separated locations on earth, which typically entail climate patterns that span thousands of miles.”
Basically, something that’s far away from a location that can influence what goes on in said location.
There are lots of different teleconnections, the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the Madden-Julian Oscillation (MJO), and more – but in this case, we’re focusing on the El Niño-Southern Oscillation (ENSO).
The El Niño-Southern Oscillation, which I’ll just refer to as ENSO (don’t need finger cramps), focuses on the sea-surface temperatures in an area in the central and eastern tropical Pacific Ocean.
The exact location in the Pacific to look at the sea-surface temperatures was debated for a while. Everyone eventually came to an agreement to use parts of both the Niño 4 and Niño 3 region and named it the Niño 3.4 region – how creative.
ENSO can be in three different phases, Neutral, El Niño or La Niña.
The Relative Oceanic Niño Index (RONI) keeps a running 3-month mean sea surface temperature anomalies in the Niño 3.4 region.
When RONI is between -0.5°C and +0.5°, this is classified as a Neutral phase.
El Niño is dictated by a positive RONI greater than or equal to +0.5°, while vice versa, La Nina is set by a negative RONI less than or equal to -0.5°.
“By historical standards, to be classified as a full-fledged El Niño or La Niña episode, these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons. CPC considers El Niño or La Niña conditions to occur when the monthly relative Niño 3.4 departures meet or exceed +/- 0.5ºC along with consistent atmospheric features. These anomalies must also be forecasted to persist for 3 consecutive months.” – Climate Prediction Center
Our most recent RONI value from June-August is 1.4°C, so we are nearly an entire degree above the threshold for El Niño.
And this will likely be a relatively longer El Niño, with it essentially being a lock that this continues thru Spring of 2027.
Long story short, El Niño is when the waters in the central and eastern tropical Pacific Ocean are warmer than average for an extended amount of time.
What Makes It A “Super” El Niño?
That’s certainly been all the buzz recently.
The strength of an El Niño all depends on just how warm the running 3-month mean ONI values are.
The categories are:
- Weak: 0.5-0.9°C
- Moderate: 1.0-1.4°C
- Strong: 1.5-1.9°C
- Very Strong: 2.0°C+
According to the Climate Prediction Center, there’s a 90%+ chance of a Very Strong El Niño this Fall thru the beginning of next year (2027). While El Niño will likely stick with us thru the Spring, it will likely weaken a bit into the Moderate to Strong category.
Just how strong will this El Niño get?
Although “Super” isn’t an official category, it’s fairly deserved for this one. During October thru December, the Climate Prediction Center gives it a 75% chance to be the strongest El Niño dating back to 1950.
RONI values are expected to get north of 2.5°C, possibly up to 3.0°C. The 2015-2016 Winter will be the one to beat, with a RONI value of 2.75°C recorded.
So, What Does This Mean For Winter In Middle TN?
While this “Super” El Niño will certainly have an impact on our weather, there isn’t one definitive answer. It doesn’t guarantee a ton of snow or a bunch of severe weather.
In a typical El Niño winter pattern, the Pacific Jet Stream usually tracks along the Gulf Coast, bringing generally above-average precipitation with below-average temperatures to the Southeast. Usually, here in Tennessee, we are just to the north of those impacts, with precipitation typically around average and temperatures leaning slightly cooler than average.
However, this is far from a “typical” El Niño.
If we look at the past seven strong El Niños, we don’t see too much of a difference here locally.
In terms of precipitation anomalies, we are sandwiched right in the middle – with drier than average just to our north and wetter than average off to the south.
And temperatures leaning slightly below average…
However, what if we narrowed it down even further, and only looked at the 3 El Niños since 1950 that have qualified for “Very Strong”, 2.0°+ RONI values.
This would be looking at the Winters of 1982-1983, 1997-1998, and 2015-2016. Small sample size, but worth a look.
The Winter (December thru February) of 1982-1983 was a fairly quiet one.
December started the winter off wetter and warmer than average. Temperatures were about 6° above average and rainfall roughly 2″ above average. We only saw 0.4″ of snow on the 11th.
January of 1983 brought slightly below average temperatures with below average precipitation. There was only one day with measurable snowfall, 0.3″ on the 20th.
February followed suit, with slightly below average temperatures and precipitation. Again, there was only one day with measurable snow, 0.8″ on the 5th.
So by all standards, a fairly quiet winter. Nothing crazy with 1.5″ of snow throughout the winter. There were also zero recorded tornadoes.
Onto the Winter of 1997-1998.
December of 1997 brought temperatures just below average, with precipitation also below-average by about 2″. Nashville did see 2.3″ of snow that month, which fell on two back-to-back days, the 29th and 30th.
January of 1998 was a fairly benign month. Temperatures were a few degrees above average, while precipitation was right around average. None of that precipitation came in the form of measurable snowfall. The exception to the benign month was an EF-1 tornado that occurred in Coffee County (to our SE) on January 7th.
February couldn’t have been a more average month, at least for Nashville. Both temperature and precipitation were nearly on top of the averages. Nashville got exactly 1.5″ of snow, which is, you guessed it, exactly average. Folks just off to our north and off to the Plateau were a lot “luckier” in terms of snowfall from that event, with some getting around a foot of snow.
And last but certainly not least, the winter of 2015-2016 – which, I’m sure some of you can remember quite well.
December of 2015 was a warm one. In fact, it was the second warmest December on record, about 10° above average. We hit 70°+ 11 days out of the month, setting 5 daily record highs. We hit 76° twice, which is only three degrees off of the all-time December record of 79°.
In terms of precipitation, we were just ever-so-slightly above average for the month. However, some of you may recall the severe weather we saw near the end of the month.
December 23 featured a tornado outbreak in Middle TN, including a long-tracked EF-3 that started in Wayne County and ended in Maury County.
We certainly turned the page in January of 2016. Although temperatures for the month were around average, along with precipitation being below average, we saw quite the snow event from the 22nd thru 23rd.
The biggest snow Nashville had seen in 28 years featured 8″ of being measured at BNA, along with 7.1″ at NWS Nashville in Old Hickory. Pretty much everyone in Davidson Co. saw at least half a foot of snow.
The only other snow we saw that month was just 2 days prior, when just 0.2″ was measured at the airport. We certainly got a season’s worth in one go.
February calmed down a bit, with both temperatures and precipitation right around average for us. The only notable event during the month was some flash flooding on Groundhog Day that impacted areas just off to our west in Dickson County, with some areas receiving 4-5″ of rain. BNA only recorded around one inch of rain during this time.
So, what does all this mean?
Well, it depends on how you look at it. The first two Very Strong El Niños were fairly calm winters overall. However, the third and most recent was certainly busier.
I think the biggest takeaway is that this guarantees nothing. There are a lot of “predictions” out there and quite frankly some of them are ridiculous, likely just looking for clicks and engagement.
Sure, the Southeast could certainly see a busier winter, but the pattern favors that for places further to our South along the Gulf coast.
Whatever the weather is, we’ll be watching and keeping y’all updated with the latest. Be sure to follow us on all of our socials to stay up to date! We’re on X/Twitter, Threads, Instagram, Facebook, Bluesky, YouTube and TikTok!
Categories: Featured Blog
