Part 1: What is El Niño, and how does it impact Colorado weather on average?
DENVER — We’re almost two-thirds of the way through the winter months. So, up this point, how do the effects of this winter’s strong El Niño pattern compare to how El Niño winters have played out across the state of Colorado in the past?
We’ll walk you through the whole process in two parts. Part 1 will dive into the details of what El Niño is and how it typically affects our weather in Colorado. Part 2 will look at how Colorado weather has reacted to this latest El Niño period.
We start by asking: What is El Niño?
El Niño is a phase of the El Niño Southern Oscilation. ENSO is a naturally occurring phenomenon that involves fluctuating surface temperatures in the tropical Pacific Ocean.
La Niña is referred to as the cold phase, or the period in which sea surface temperatures are below average. Conversely, El Niño is referred to as the warm phase, or the period in which sea surface temperatures are above average.
El Niño and La Niña periods typically last nine to 12 months. While their frequency can be irregular, El Niño and La Niña events occur roughly every two to seven years. On average, El Niño occurs more frequently than La Niña.
In summer 2014, there was an uptick in the sea surface temperatures over the Pacific. Ever since, those temperatures have continued to climb, taking it from a weak El Niño pattern into the very strong El Niño pattern we have experienced throughout the winter so far.
El Niño’s effects are strongest during winter months in the Northern Hemisphere. The warmer ocean waters lead to more storm development, which in turn, shifts the jet stream.
This shift then transfers Pacific moisture to different parts of the country than in non-El Niño winters and in certain regions, creates abnormal temperature patterns.
Typically, Colorado winters aren’t drastically affected by an El Niño pattern. Statistically, the correlation between temperature variations and El Niño patterns are minimal.
Overall, average precipitation amounts statewide don’t vary much either. However, the location of where most of the precipitation falls is a different story.
During an average El Niño pattern, the majority of moisture transported onshore from the Pacific shifts southward, into the southwestern United States. This leads to an increase in precipitation amounts across the southern half of Colorado.
As a result, during the winter months, the mountains of southwest Colorado typically see the highest snow totals throughout the state. During winter months in which La Niña conditions are observed, or during neutral periods, higher snowfall totals usually shift back to the northern part of western Colorado.
Keep an eye out for Part 2: How Colorado weather has been affected by this winter’s strong El Niño pattern.