May Climate Briefing: ENSO-Neutral Conditions Dominate

Authored by Jacquelyn Turner on May 26, 2020

Read our ENSO Essentials & Impacts pages for more about El Niño and La Niña.

As of mid-May, the sea surface temperatures had decreased to cool-neutral levels, while atmospheric indicators showed mainly neutral or slightly cool-leaning conditions. A new set of model runs predicts neutral conditions are most likely from summer through winter, with a 51% probability for ENSO-neutral for the Aug-Oct season (and 30% and 20% chances for La Niña and El Niño, respectively). This outlook calls for somewhat lower chances for La Niña for fall and winter than the official ENSO forecast issued May 14, which used both models and human judgement.

Weston Anderson provides the briefing summary:

What’s New

See below for tweets summarizing the current El Niño situation.

The latest weekly Nino3.4 SST anomaly is -0.4ºC, which is within the neutral ENSO range. This map and more in our data library: https://t.co/sxpdQ5lhvl. + More about ENSO: https://t.co/GldQNBgs3D. pic.twitter.com/vjNOrAIEkm
— IRI (@climatesociety) May 26, 2020

Important cooler-than-normal sub-surface heat content anomalies in the equatorial Pacific could lead to a #LaNiña in a few seasons, but we still need to see if that could materialize. @climatesociety #briefing pic.twitter.com/h3jFwSVIny
— Ángel G. Muñoz (@agmunozs) May 21, 2020

Cold subsurface ocean heat content mean that cooling SSTs in the Eastern Pacific are likely to continue, at least in the near term. Model forecast is for a weak-moderate La Niña, although large uncertainty remains@climatesociety #IRIforecast pic.twitter.com/pO4wJmSLS1
— Weston Anderson (@HydroClim) May 21, 2020

ENSO Forecasts

To predict ENSO conditions, computers model the SSTs in the Niño3.4 region over the next several months. The plume graph below shows the outputs of these models, some of which use equations based on our physical understanding of the system (called dynamical models), and some of which use statistics, based on the long record of historical observations.

Our model plume w/ @NWSCPC for April and May. #IRIforecast pic.twitter.com/ZGFcqSfr3A
— IRI (@climatesociety) May 21, 2020

The probability for El Niño conditions to continue has dropped to around 40% for the remainder of the year. The La Niña odds are lower in the official probabilistic forecast issued by the U.S. Climate Prediction Center (CPC) and IRI in early May than in the mid-month IRI/CPC forecast. The earlier forecast uses human judgement in addition to model output, while the mid-month forecast relies solely on model output. More on the difference between these forecasts in this IRI Medium post.

ENSO in context: Resource page on climate variability

IRI’s Global Seasonal Forecasts

Each month, IRI issues seasonal climate forecasts for the entire globe. These forecasts take into account the latest model outputs and indicate which areas are more likely to see above- or below-normal temperatures and precipitation.

All forecast maps, including temperature in addition to precipitation, and also including a description of the methodologies, are available on our seasonal forecast page. Additional forecast formats, such as our flexible forecast maproom, are available in the IRI Data Library.

Learn more about El Niño and La Niña on our ENSO resources page, and sign up here to get notified when the next forecast is issued. In the meantime, check out #IRIforecast.