Weather Insider: How ENSO affects drought in the Southwest

For most of the last few decades, the Southwest United States has been in a long-term 'megadrought'. The atmospheric river events of the last two winters have greatly helped to improve drought conditions across the Southwest. However, it wasn't quite enough to remove drought conditions throughout the entire region. For some context, in mid-March of 2024, about 25% of the region was under some form of drought. However, roughly 90% of the region was under some form of drought during the same time in 2022 and 2021.

But what impact does ENSO (El Nino Southern Oscillation) have on the sought in the Southwest? As a reminder, ENSO is the name for the climate cycle that causes El Nino and La Nina and is determined by sea surface temperatures in the equatorial Pacific. Repeated research has shown that El Nino patterns are associated with wetter and cooler winters for the Southwest as well as higher daily precipitation and streamflows. Heavy precipitation events are also more likely during El Nino setups. The inverse has been associated with La Nina. As of the latest update (August 8th, 2024), there is a 66% chance of La Nina forming sometime between September and November.

ENSO is just one piece of a highly complicated puzzle and should never be taken alone when making a projection for an entire season. There are countless other factors to consider such as other climate cycles, their interactions with each other, and many more. However, most signs are pointing to a drier-than-usual fall and winter for the Southwest and much of the southern tier of the nation, as indicated by the various shades of brown on the maps below.

You can learn more information here: https://www.climate.gov/news-features/blogs/enso/enso-and-southwest-united-states-megadrought