ENSO and Colorado

The El Niño - Southern Oscillation (also known as ENSO) refers to a cyclical pattern observed in the tropical Pacific Ocean. There are three phases of ENSO - El Niño, La Niña, and Neutral. These phases relate to the ocean temperature anomalies that are occurring at any given time. If the ocean temperatures in the tropical Pacific are much warmer than average, then we are in an El Niño phase. If the temperatures are colder than average, we're in a La Niña. Climate.gov provides details on how exactly El Niño and La Niña conditions form. Read more...

El Niño Phase
La Niña Phase

The below graph shows how the ENSO phase has changed (or oscillated) over time. A couple of the strongest El Niño events include 1997 and 1982-83. Stronger La Niña events occurred in 1988 and 2011-2012. NOAA's Earth Systems Research Laboratory gives a nice discussion about past El Niño and La Niña events. Read more...

It's hard to believe, but the changing temperatures in the Pacific Ocean can impact weather all across the globe! Over the United States, for example, El Niño conditions can result in a wet winter for the southeast and a dry and warm winter in the Pacific Northwest. This happens because those changing ocean temperatures drive changes in atmospheric pressure, the jet stream, and overall weather patterns. The North Carolina State Climate Office has a great ENSO page that discusses ENSO impacts on the U.S. Read more...

Typical Winter El Niño Impacts
Typical Winter La Niña Impacts

For Colorado, the story is a little more uncertain. The complex topography of our state, our distant location from the oceans, and our sensitivity to a lot of other variables, means that ENSO competes with a lot of other forces in determining what our weather will be like! So, while ENSO does play a partial role in Colorado's climate, it's not always a guarantee.

Explore the links below to see how El Niño and La Niña impact temperature and precipitation anomalies around the United States.

El Niño & Temperature
November - March
May - September

La Niña & Temperature
November - March
May - September

El Niño & Precipitation
November - March
May - September

La Niña & Precipitation
November - March
May - September

For Colorado, you may notice that the strongest signal shows up in wintertime temperature anomalies during an El Niño, when the entire state is likely to experience overall below average temperatures. During a La Niña, the eastern plains are more likely to see above average temperatures in the winter and summer.

When looking at precipitation, there's even more uncertainty! The most dominant signal shows up during La Niña summers. At that time, much of Colorado has tended to experience slightly below average precipitation.

During an El Niño, no signal shows up over Colorado. This may be surprising for some of you. Thinking back to winters of the past during particularly strong El Niños (like 82-83 or 97-98) you may associate major Front Range blizzards with those seasons. And when you look at the years in the composite, you'll see that one of our largest blizzards (March 2003) also occurred during an El Niño year. But that signal is just not consistent enough to solely attribute it to ENSO or use it as a forecast for future El Niño winters.

Current ENSO Conditions

Current sea surface temperature anomalies in the tropical Pacific Ocean

CPC/IRI PUBLISHED February 19, 2018 - In mid-February 2018, the tropical Pacific reflected La Niña conditions, with SSTs in the east-central tropical Pacific in the range of weak to moderate La Niña and most key atmospheric variables showing patterns suggestive of La Niña conditions. The official CPC/IRI outlook calls for La Niña continuing through at least early spring, followed by a likely return to neutral conditions around mid-spring. Support for this scenario is provided by the latest forecasts of statistical and dynamical models. Read More...


Potential Impacts

In Colorado winter La Niña tends to favor warmer, drier conditions to the south and colder, wetter conditions to the north. This correlation certainly isn't a perfect indicator, but for this winter, it has panned out that way. Note that future Climate Prediction Center outlooks may trend toward that pattern. Current outlooks for the spring are favoring warmer than average conditions across our entire state, and drier than average for most of the state. But we're actually looking at an increased chance for some colder and wetter than average spots for the next month.


Read the latest ENSO blog entry at Climate.gov - February 2018 La Niña update: tuned in
"...While this La Niña's effect on precipitation and temperature has been generally in-line with expectations over North America, especially regarding the dry conditions across the southern half of the US, global impacts haven't been entirely as expected during the past few months..."