June Climate Briefing: Neutral, For Now
Read our ENSO Essentials & Impacts pages for more about El Niño.
Tony Barnston provides an overview of the briefing
The El Niño event that began in spring 2015 has come to an end. Sea-surface temperatures in the equatorial region of the Pacific Ocean that define El Niño and La Niña events, called the Nino3.4 region, have been in the neutral category for over a month. On June 9, the National Oceanic and Atmospheric Administration’s Climate Prediction Center issued the final El Niño advisory, and the La Niña watch issued in June is still in effect.
Changes from last month’s briefing
In May, the monthly average sea-surface temperatures in the Nino3.4 region dipped below the 0.5ºC mark that scientists consider the threshold of a El Niño for the first time since October of 2014. At 0.3ºC above average, the temperature was well within ENSO-neutral conditions. In the last several weeks, the weekly-averaged sea-surface temperatures have dropped further, hovering around the 0ºC mark. See the latest SST measurements in the first image below. [Note: For many reasons outlined in this NOAA blog post, comparison of SSTs between datasets (and sometimes even within the same dataset!) should be cautious, largely due to variation in data collection methods and resolution of the datasets. Further, the dataset used for the above statistics (called OISSTv2) is not the one used in NOAA’s records for official peak strength (called ERSSTv4), though OISSTv2 is the one used in initializing models.]
To predict El Niño, computers model the SSTs in the Nino3.4 region over the next several months. The graph in the second image of the gallery 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.
The dynamical model mean calls for a slightly weaker La Niña event compared to last month’s forecast, while the statistical model mean calls for a slightly stronger (though still weak) La Niña event compared to last month. The spread of the model outputs is narrower than the May forecast’s spread. Dynamical models indicate an immediate shift to near-La Niña conditions for the June-July-August season, while the statistical models call for a more gradual dip, with the La Niña threshold of -0.5ºC not being reached until the September-October-November season.
Based on these model outputs, chances for La Niña development in the latter half of 2016 are up slightly from last month, with odds in the 60-65% range for the September-October-November period, as well as the following seasons (see third graph in gallery above).
The probabilistic forecast issued by CPC and IRI in early June shows somewhat higher odds for La Niña conditions. This early-June forecast uses human judgement in addition to model output, while the mid-June forecast relies solely on model output. Forecasters think the statistical models may be underestimating the likelihood for La Niña conditions and thus increased the odds for La Niña in the early-June forecast.
Effects of El Niño on global seasonal forecasts
Each month, IRI issues seasonal climate forecasts for the entire globe. These forecasts take into account the latest sea-surface temperature projections and indicate which areas are more likely to see above- or below-normal temperatures and rainfall.
For the upcoming July-September period, the forecast shows some likelihood of drier-than-normal conditions over areas of the northwestern United States and the western Amazon region (first image in gallery above, click to enlarge). The forecast also shows an elevated chance of above-average precipitation in Indonesia. Eastern Australia as well as parts of North America show a slightly elevated chance of above-average precipitation.
El Niño in context: Resource page on climate variability
The impacts listed above are specifically for the July-September season. For the later seasons, which show more signs of La Niña influence, see forecast maps in the image gallery and on our seasonal forecast page.
Learn more about El Niño on our ENSO resources page, and sign up here to get notified when the next forecast is issued. In the meantime, check out #IRIforecast or use #ENSOQandA on Twitter to ask your El Niño questions.