April 2014 Climate Briefing: El Niño Likely, Strength Uncertain

From the April climate briefing, given by IRI’s Chief Forecaster Tony Barnston:

Tony Barnston provides an overview of the briefing

Changes from last month’s briefing

The IRI/CPC probabilistic ENSO forecast issued mid-April 2014. Note that bars indicate likelihood of El Niño occurring, not its potential strength. Unlike the official ENSO forecast issued at the beginning of each month, IRI and CPC issue this updated forecast based solely on model outputs. The official forecast, available at http://1.usa.gov/1j9gA8b, incorporates human judgement.

El Niño Southern Oscillation (ENSO) conditions are currently neutral, although the warming process has begun. The IRI’s April ENSO forecast puts the chances of El Niño conditions at more than 70% for early next fall (see image at right), an increase from the 60% probability in IRI’s March forecast and  the 61% probability from NOAA/IRI’s official prediction issued on April 10. According to the updated IRI forecast, the probability increases to 75-80% by autumn.

Although the odds for El Niño are increasing, it is still uncertain whether it will be a weak, moderate, or strong El Niño. This uncertainty lies in what is known as the “spring predictability barrier.” During April, May, and June, the state of the central Pacific is dynamic and can change quickly, making it hard to predict how it will behave in the coming months. In June, predicability of the El Niño, including its potential strength, will become more certain. 

Effects of El Niño on global seasonal climate forecasts

Each month, IRI issues seasonal climate forecasts for the entire globe. These forecasts, which take into account the latest ENSO projections, indicate which areas are more likely to see above or below normal temperatures and rainfall. The latest forecasts are showing moderate impact to climate in areas typically influenced by El Niño  (view the seasonal forecasts here). The area with the strongest chance for below-average rainfall is Indonesia. 

Scientists should know more each month about the chances for El Niño, its potential strength, and the climate impacts. Sign up here to get notified when the next forecast is issued, and in the meantime, check out #IRIforecast or use #ENSOQandA on Twitter to ask your El Niño questions.