What is La Nina and How Might it Affect the State’s Weather?
Everyone is accustomed to hearing the terms El Nino and La Nina and how they relate to weather activity. But even though most are familiar with the terms, some are confused as to what the weather-related phrases exactly mean and how the occurrences can change weather patterns.
As most also know, the weather a region will get in any particular season has to do with currents in the Pacific Ocean. Every few years, the currents naturally change and give us El Nino or La Nina current patterns. These opposite changes in currents then play a role in weather patterns and air currents in the U.S.
This winter, many news sources have reported that La Nina will be returning to the country for the third year in a row. The fact that La Nina weather patterns are expected to exist is not uncommon, but the fact that it is slated to return for a third year makes it a rather rare occurrence. And, many say Colorado could be negatively affected this season.
What is La Nina and El Nino?
According to the National Oceanic and Atmospheric Administration (NOAA), trade winds naturally blow along the equator pushing warm water from South America toward Asia. The warm water then gets replaced by cold waters rising from deep in the ocean during a process coined as upwelling. El Nino and La Nina are “two opposing climate patterns” that disrupt the normal conditions in the Pacific Ocean.
The weather pattern El Nino occurs when the trade winds weaken and warm water gets pushed east to the west coast of America. “The warmer waters cause the Pacific jet stream to move south of its neutral position,” the NOAA reports on its website. “With this shift, areas in the northern U.S. and Canada are dryer and warmer than usual. But in the U.S. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding.”
When La Nina occurs, the opposite effect happens as trade winds get stronger than usual and push more warm water toward Asia. “This tends to lead to drought in the southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada,” the NOAA reports. “During a La Niña year, winter temperatures are warmer than normal in the South and cooler than normal in the North.”
How Will the Return of La Nina Impact Colorado?
According to Climate.gov, there is a 75 percent chance that La Nina will return to the Pacific Ocean for the third year in a row. Since La Nina strengthens the normal atmospheric circulation across the Pacific, high pressures systems will develop in the Northeast Pacific. The high pressure can then alter the flow of storms and it will often create wet winters in the northwest and dry winters in the South.
An article published by 5280.com, explains that Colorado could be negatively impacted this year. The ’20-’21 winter produced more snow for Denver but many mountainous areas of the state including the San Juan Mountain Range recorded below-average snowfalls.
During a La Nina weather pattern, Colorado, along with other areas in the southwestern part of the country, often sees milder dry winters. This dry spell is known to make drought conditions worse and increase the chances of wildfires. And the fact that La Nina is returning for a third year could exasperate conditions and make drought conditions even worse than when La Nina normally strikes.
The article reports that since people started keeping records of La Nina and El Nino weather patterns in 1950, there have only been two instances before this year that La Nina has returned for three years in a row. Since drought conditions are already a serious concern for many parts of the state, low snowfall numbers could make matters even worse.
Colorado was negatively impacted the last two times La Nina came three years in a row with the first one starting in the spring of 1973 and ending in the spring of 1976, and the last one starting in the summer of 1998 and ending in the spring of 2001. “The winter of 1976-’77 left most mountain locations with a four- to the seven-foot deficit by the end of the season,” 5280.com reported last June. “The winter of 2001-’02 left most mountain locations with a 2- to the 4-foot deficit.”
Despite La Nina Colorado Snowpack Numbers Sit Above Average
Even though forecasters seem to expect a mild winter this year, everyone who lives in the state knows that weather in Colorado can be unpredictable. In fact, by the time 2023 started many areas in the state were already seeing above-average snowpack levels.
According to an article published by CBS Colorado on Jan. 4, snowpack levels are sitting higher than average at this time of year in six of Colorado’s eight river basins. Only two basins remained below normal snowpack levels and those were the Arkansas Basin which includes most of the south and southeastern part of the state and the Upper Rio Grande Basin which encompasses the San Luis Valley in the south-central part of Colorado.
These two regions have seen below-average snowpack levels due to the fact that most of the recent storms have missed the Sangro de Cristo and Wet Mountains near Canon City, Walsenberg and Trinidad. However, in the northwestern part of the state, the Yampa and White River Basins have seen nearly 50 percent more than the average snowpack numbers.
Colorado residents hope that this means that the state will see higher snowfall numbers for the rest of the season contrary to what several meteorologists have forecasted. If snowpack levels remain above average into the spring season, Colorado should see fewer drought conditions and a less severe wildfire season in 2023.
