Winter in Sedona, Arizona.
Institute of the Environment 2017

UA Researchers Launch Guide to Understanding El Niño

Monday, December 21, 2015

By Paulina Jenney, Instititue of the Environment

It’s been heralded as the Godzilla El Niño, but researchers at the University of Arizona want to assure you that the climate force forecast to pummel North America this winter is no monster. Instead, they say, this wet season could bring cooler temperatures and record rain and snow to the Southwest in a natural oscillation that occurs every two to seven years.

The prospect of high rainfall totals and drought relief have taken the public and media by storm, prompting the Climate Assessment for the Southwest, or CLIMAS, program to launch the El Niño-Southern Oscillation (ENSO) Hub, a Web page for all things El Niño.

           Five things to know about the 20152016 El Niño

  • El Niño is still on track, and the best is yet to come. In the Southwest, El Niño related storm activity typically sees the strongest effects in the late winter through early spring. We still see an increased chance of above-average precipitation in the forecast for much of the Southwest later this winter.
  • Short periods of warm and dry conditions are likely throughout the upcoming winter season, but this doesn’t mean El Niño has been canceled. El Niño is a seasonal climate phenomenon which means we must wait until the spring to judge the strength of El Niño’s cool season impacts.
  • El Niño could improve short-term drought conditions (i.e., within the month or season), but will not erase the long-term water deficits associated with our current multi-year drought. If the winter is wetter than average (as forecasted), this is a step in the right direction, but longer-term drought improvements will be measured in years not seasons.
  • El Niño related flooding is possible on larger rivers across the Southwest this spring. Flooding events in Arizona typically occur during warming conditions, when heavy rain falls on existing snow, which melts the existing snow and sends excess water cascading through our watersheds.
  • Above-average precipitation across low desert areas in October coupled with the expectation for more precipitation in December and January could result in an exceptional wildflower season this spring.

“This El Niño will be one of the top three strongest events on record,” said Ben McMahan, a research outreach and assessment specialist with CLIMAS. “People are interested in it because these kinds of strong events don’t happen very often.”

This El Niño could rival the big El Niño of 1997-1998, when just under 8 inches of winter rain fell over Tucson, about 4 inches more than the average for those months. However, the scientists at CLIMAS emphasize that although this El Niño might break the record for overall winter precipitation, it doesn’t mean that Tucson should expect a consistent deluge.

“A lot of the forecast models and media coverage give people the impression that it’s going to rain every day, but when you talk to the forecasters and climate scientists, none of them think that’s likely to happen.,” McMahan said. “We might have some severe weather, but we might also have some below-average months, too. But overall we expect above average rainfall this winter.”

To help people understand what El Niño might have in store, McMahan and climate science extension specialist Mike Crimmins devised a Web page containing information pulled from the National Weather Service, the Western Regional Climate Center, and other regional climate datasets, as well as an El Niño podcast, FAQ’s, predictions, and even a live Twitter stream.

“Some of what we’re trying to do is be responsive to the speed at which information flows on the Internet without getting caught up in the hyperbole of it,” McMahan said. “It’s a balance between coming up with information that’s compelling, that’s interesting to people, that has some type of narrative, but doesn’t necessarily engage in extreme language.”

The Hub includes basic facts about the El Niño-Southern Oscillation, a natural see-saw in oceanic sea surface temperatures and surface air pressure between the east and west tropical Pacific Ocean; graphs and charts, and timely articles written by CLIMAS scientists about topics that are relevant to the general public about regional climate.

In addition to targeting the everyday weather enthusiast, the ENSO Hub is designed as a resource for stakeholders and decision makers in Arizona, New Mexico and the borderlands region, providing background and context to better understand the El Niño phenomenon.

“We’ve pulled together a mix of maps and models and projections, and then we’re adding interpretations and commentary about how they might matter to people in the Southwest. So a visitor to the page might be someone who is just interested in seeing what’s coming, but it might also be a range manager who wants to think about the condition of their land for the next six months,” McMahan said. “We’re trying to bring together materials that we think are important in explaining El Niño, in a centralized hub on the CLIMAS website.”

And after the El Niño season has passed?  The team plans to continue providing information about the current weather patterns, especially if the trend swings back to La Niña, a period of less precipitation and possible drought.

“We’ll still have a subpage that links to the El Niño information,” McMahan said, “because it is a cycle.”