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How La Niña could affect Colorado’s severe weather season

The nearly two-year La Niña weather pattern appears to continue into the summer months, according to the Climate Prediction Center. Just as in winter, when La Niña can affect our snow and hail, in spring, La Niña can affect severe weather and temperatures.

La Niña is part of a weather phenomenon known as ENSO, or El Niño Southern Oscillation. This indicates whether sea surface temperatures in the tropical Pacific are cooler (La Niña) or warmer (El Niño) than average – or near-normal, which is known as ENSO neutral.

We have been in the La Niña region since mid-2020, and current forecasts show that La Niña conditions will continue through this summer with a trend toward neutral conditions. Weak El Niño conditions are likely to develop by the end of this year, but we are more likely to stay near neutral than anything else.

ENSO Outlook to 2022

As we move deeper into the spring months, we’ll start to see more severe weather unfold nearby. Here’s a look at when any form of severe weather (hail, tornadoes, damaging winds) begins to make its way into Colorado.

Possibility of severe weather in June
Possibility of severe weather in late May
Possibility of severe weather in late April

By the end of April, some severe weather is likely in far eastern Colorado. By the end of May we are starting to receive more severe storms more frequently, and by mid-June we are in full severe weather season.

With La Niña likely to continue through July and August, how will it affect our severe weather?

As we’ve already seen in parts of the Deep South, this has been a very active start to the severe weather season. During spring in the La Niña pattern, what happens is that the jet stream ends cutting off the northern third of the United States During spring, when temperatures rise toward the south, the thermal gradient of the air masses created turns into a recipe for severe weather.

Eventually, the jet stream will begin to move north, but due to La Niña, it may not retreat as far north as it usually does at this time of year.

An overview of the implications of La Niña or El Niño

With the jet stream not retreating to the north as often as normal over the next few months, we will have cooler air nearby which will allow stronger cold fronts to push toward the warmer, wetter south. The collision of these air masses helps to spread severe weather outbreaks and this setup allows this to happen more often.

There is no causal link when talking about the effects of severe weather during La Niña but there are some salient points that go along with the above thinking. Nationally, some of the most active severe weather seasons in the past 30 years have occurred during the La Niña years: 2011, 2008, 1998, and 1995 all led to severe weather effects while the La Niña phenomenon persisted.

Number of severe thunderstorm and hurricane warnings issued in Colorado annually

Of the first 10 years with the most severe thunderstorm and hurricane warnings in Colorado, seven were La Niña years and three were El Niño years.

Also, one thing to note, all of our most productive severe weather years have occurred since 2000. When we look nationally, during La Niña, there is extreme weather across Texas, Arkansas, and Oklahoma.

Severe Weather Trends During LA Niña and El Niño . Patterns

For Colorado, there is no compelling evidence that we will experience a markedly extreme weather season due to the persistence of La Niña, but there are differences that we can detect.

Severe weather tends to be slightly suppressed statewide when El Niño is present. While Colorado isn’t far from what’s normal in a La Niña pattern, we’re headed toward the more casual side of things when talking about hurricanes. Mountainous locations and southern Colorado tend to increase hail fears a bit during a La Niña pattern.

Temperatures and precipitation can also be affected by the ongoing La Niña, but the effects are not as noticeable as they are in the winter months. In the warmer months, ENSO tends to have more effects on hurricane season than anything else. With that said, the longer-term outlook for April through June shows signs of drier and warmer across Colorado.

Expect anomalies in temperature and precipitation during April, May and June
Expect anomalies in temperature and precipitation during April, May and June

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