ENSO Blog

After just a few months of La Niña conditions, the tropical Pacific is now ENSO-neutral, and forecasters expect neutral to continue through the Northern Hemisphere summer. Neutral is also the most likely state through the fall (greater than 50% chance). What is ENSO? What does neutral even mean? ENSO stands for “El Niño/Southern Oscillation,” a pattern of changes in the temperature of the ocean surface and atmospheric circulation of the tropical Pacific region. La Niña means the surface water is cooler than average, the trade winds are stronger, and the central equatorial Pacific receives less rain. On the other hand, El Niño is represented by warmer surface water, weaker trade winds, …   Read article

While many of us in the U.S. are reveling in the excitement of college basketball tournaments and trying to win our March Madness pools, it’s also a good time to look back at this past winter’s (December 2024– February 2025) precipitation pattern over North America. Were the seasonal forecast models a winner or a bust this winter? Was La Niña a star or a benchwarmer? Let’s go to the videotape! Pre-Season polling Early last December, I wrote about the predicted winter North American precipitation pattern from a group of state-of-the-art computer forecast models, the North American Multi-Model Ensemble (NMME). At that time, I argued that the forecasted precipitation pattern was…   Read article

La Niña conditions persisted through February, but forecasters expect ENSO-neutral conditions to develop in the next month and persist through the Northern Hemisphere summer. ENSO La Niña is the cool phase of the El Niño/Southern Oscillation, or ENSO, a pattern of changes in the tropical Pacific Ocean and the atmospheric circulation over the tropical Pacific that persists for many months. La Niña’s signature is cooler-than-average surface water in the east-central tropical Pacific, stronger-than-average trade winds, more rain and clouds over Indonesia, and drier conditions over the central Pacific. El Niño is the opposite, with warmer-than-average surface water and weaker atmospheric c…   Read article

In the, roughly, 250 years of the ENSO Blog and our 3.4 million posts, we’ve discussed ad nauseum how complicated El Niño and La Niña are, and how difficult it is to forecast all of the ENSO nuances. Heck, I even wrote a three-part series 75 years ago that evaluated all of our seasonal forecasts (ok, it was 2014-2015 but it still feels that long ago). In a new paper, Azhar Ehsan, friend of the blog and a member of NOAA’s ENSO forecast team, and colleagues analyzed over 20 years’ worth of climate model forecasts of ENSO and found some interesting results. Why is this paper unique? Well, most seasonal forecasting evaluations focus on model hindcasts, which are forecasts run using past obser…   Read article

La Niña conditions continue, but forecasters estimate a 66% chance of a switch to neutral in March–May. This is looking like a weak and short La Niña. Also, while La Niña’s ocean conditions are currently weak, the atmospheric component is fairly strong. Today, I’ll cover current conditions, the forecast, and that mismatch between the ocean and atmosphere across the tropical Pacific Ocean. Live in the moment La Niña and its counterpart El Niño make up the El Niño/Southern Oscillation, or ENSO. La Niña’s characteristic cooler-than-average tropical Pacific surface water changes global atmospheric circulation in known ways, providing an early picture into potential upcoming temperature, ra…   Read article