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Published April 24, 2013
El Niño Status and ForecastData Source(s): NOAA-Climate Prediction Center (CPC), International Research Institute for Climate and Society (IRI)
Sea surface temperatures (SSTs) in the equatorial Pacific Ocean did not substantially change in the last month, and ENSO-neutral conditions are still present. In the last 30 days, SSTs remained very close to average across much of the equatorial Pacific basin, with the only notable changes occurring in the eastern Pacific where temperatures rose slightly. The Southern Oscillation Index (SOI) is also indicating neutral conditions (Figure 14a). This may have been caused by a relatively fast-moving atmospheric oscillation, called the Madden-Julian Oscillation, which moved across the Pacific Ocean in recent weeks and caused SSTs and wind patterns to change slightly, according to the NOAA-Climate Prediction Center (CPC). The warming is not signaling a shift to El Niño conditions; rather, it is a short-term response to other temporary forces. Wind and precipitation patterns across the Pacific from east to west continue to signal that neutral conditions still hold sway.
Official ENSO outlooks issued jointly by the CPC and the International Research Institute for Climate and Society (IRI) strongly indicate that ENSO-neutral conditions are the most likely outcome during the next several months (Figure 14b). There is greater than a 70 percent chance that neutral conditions will persist through July, an increase in odds from 64 percent forecasted last month. Neutral conditions also remain high through the end of the summer. The CPC notes that longer-lead forecasts—those issued for late summer and beyond—are more uncertain during this month because models have difficulty simulating the initial evolution of ENSO, a modeling phenomena known as the spring predictability barrier. Nonetheless, it is likely that ENSO will not be a major control on weather patterns this summer.
The first figure shows the standardized three month running average values of the Southern Oscillation Index (SOI) from January 1980 through March 2013. The SOI measures the atmospheric response to SST changes across the Pacific Ocean basin. The SOI is strongly associated with climate effects in the Southwest. Values greater than 0.5 represent La Niña conditions, which are frequently associated with dry winters and sometimes with wet summers. Values less than -0.5 represent El Niño conditions, which are often associated with wet winters.
The second figure shows the International Research Institute for Climate and Society (IRI) probabilistic El Niño-Southern Oscillation (ENSO) forecast for overlapping three month seasons. The forecast expresses the probabilities (chances) of the occurrence of three ocean conditions in the ENSO-sensitive Niño 3.4 region, as follows: El Niño, defined as the warmest 25 percent of Niño 3.4 sea-surface temperatures (SSTs) during the three month period in question; La Niña conditions, coolest 25 percent of Niño 3.4 SSTs; and neutral conditions where SSTs fall within the remaining 50 percent of observations. The IRI probabilistic ENSO forecast is a subjective assessment of current model forecasts of Niño 3.4 SSTs that are made monthly. The forecast takes into account the indications of the individual forecast models (including expert knowledge of model skill), an average of the models, and other factors.
For a technical discussion of current El Niño conditions, visit:
For more information about El Niño and to access graphics similar to the figures on this page, visit:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubious, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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