NOAA - La Nina Officially Underway; Likely To Worsen Already Critical Southwestern Drought
Climate forecasters said Thursday that the world had entered La Niña, the opposite phase of the climate pattern that also brings El Niño and affects weather across the globe. Among other impacts, La Niña has the potential this winter to worsen what are already severe drought conditions in the American Southwest.
The Climate Prediction Center, a part of the National Oceanic and Atmospheric Administration, said in its monthly forecast that sea-surface temperatures in the central and eastern tropical Pacific Ocean had cooled, signifying La Niña conditions, and that there was a 75 percent likelihood that La Niña would continue through the winter.
Like El Niño, which results from warmer-than-normal ocean temperatures in the tropical Pacific, La Niña occurs every two to seven years on average. And like El Niño, it leads to changes in atmospheric circulation that can affect weather in unconnected parts of the world. La Niña’s strongest influence is usually felt in winter. And while the precise effects are unpredictable, La Niña can result in warmer and drier conditions across the Southern United States and cooler conditions in southeastern Alaska, the Northern Plains and western and central Canada. It can also lead to a wetter winter in the Pacific Northwest.
Mike Halpert, deputy director of the Climate Prediction Center, said that as a result of La Niña, Southern California, as well as most of Arizona and New Mexico, could “tilt toward dry” this winter.
EDIT
https://www.nytimes.com/2020/09/10/climate/la-nina-southwest-drought.html
Related: this is yesterday's UNL Drought Monitor:
Also related: Mead and Powell, the two largest reservoirs in America and the two on which much of the Southwest and California depend, are at 39.9% and 47.6% of capacity, respectively.
http://lakemead.water-data.com/
https://lakepowell.water-data.com/