If you’re nostalgic for New Mexico winters with lower temperatures and lots of mountain snow leading to abundant spring runoff, then here’s some good news.
The La Niña weather pattern that has dominated during the last three winters has departed and it looks like we’re heading into an El Niño weather pattern, which typically brings colder and wetter weather during New Mexico winters, said Joe Diaz, KOAT-TV’s chief meteorologist.
“It depends on where the heating is in the Pacific and where the tropical thunderstorms bubble up that impact the direct storm track as it pushes on into the southern U.S.,” Diaz said. “But every El Niño is different and generally speaking they favor southern New Mexico and then work up to the north. El Niño is not as big a player as you get to northern New Mexico on into southern Colorado.”
During a La Niña weather pattern, “winter is usually good in the mountains of Southern Colorado with the snowpack, and it’s decent in the northern part of New Mexico,” Diaz said. “But when you get to southern New Mexico, La Niñas really wreak havoc on the mountain snowpack.”
For Albuquerque, the switch to El Niño also means “more opportunities for winter moisture,” be it rain or snow, Diaz said.
The oceanic and atmospheric mechanics of La Niña and El Niño weather patterns can be a bit confusing.
Michael Anand, a meteorologist with the Albuquerque office of the National Weather Service, explained that “a La Niña occurs when the equatorial surface water off the coast of South America, which is generally pretty cold, is even colder than normal. That increases the trade winds circulation, which causes most of the equatorial convection, or thunderstorm activity, to occur in the tropics around Indonesia, Southeast Asia and East Asia.”
In the United States, La Niña causes the jet stream, the ribbon of fast-moving air in the upper atmosphere, to move farther north in latitude, resulting in storms tracking farther north and leaving the southern portion of the U.S., including much of New Mexico, to experience drier and warmer winters, Anand said.
An El Niño weather pattern “is basically the opposite of the La Niña” pattern, he said. Equatorial surface water along the coast of South America warms up rapidly, “generally increasing 1-3 degrees above average, which doesn’t sound like much, but makes a big difference.” That warming occurs when the trade winds weaken, allowing warmer waters from the Western Pacific to move toward the Eastern Pacific. That in turn causes the high altitude jet stream above the United States to shift farther south in latitude, bringing with it more winter storm activity to the southern portions of the country.
It wasn’t until earlier this month that the National Weather Service’s Climate Prediction Center formally announced that the La Niña pattern had ended, but there were signs as early as January that it was releasing its grip, Anand said.
“So it was basically over earlier this year, and that’s the reason why we’ve had this more recent active storm track over the western U.S.,” he said.
Generally speaking, the two weather patterns express themselves as winter phenomena, and have little effect on weather at other times of the year, he said.
Even though La Niña has departed, the reappearance of El Niño is not a given. “We’ve transitioned from a La Niña pattern to a neutral pattern, but we’re projecting to transition to an El Niño later this year, sometime in the fall or winter months,” Anand said.