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

An El Niño Watch was Issued June 2018
CPC/IRI PUBLISHED July 12, 2018 - In early July 2018, the east-central tropical Pacific waters reflected ENSO-neutral conditions, with slightly above average SST. The key atmospheric variables also suggested neutral conditions. The subsurface water temperature continued to be above-average. The official CPC/IRI outlook calls for neutral conditions through northern summer season, with a 65% chance of El Niño development during fall, rising to 70% for winter 2018-19. An El Niño watch is in effect. The latest forecasts of statistical and dynamical models collectively favor weak El Niño development by late summer, growing to weak or moderate strength during fall and winter; forecasters are largely buying into this scenario now that the spring barrier is largely passed. Read More...

Outlook

Potential Impacts

Our current dominant pattern of weather brings convective (and local) storms. All eyes are currently on how the monsoon will play out for our state. Given the possibility of a developing El Niño in the fall, we could see a pattern shift from what we saw last fall and winter. Stay tuned!

ENSO News

What does an El Niño Watch mean? - The El Niño and La Niña Alert System

Read the latest ENSO blog entry at Climate.gov - July 2018 ENSO update: Dog days