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Published January 23, 2013
El Niño Status and ForecastData Source(s): NOAA-Climate Prediction Center (CPC), International Research Institute for Climate and Society (IRI)
After flirting with El Niño conditions in early fall 2012, sea surface temperatures (SSTs) have trended back to near-average levels across almost all of the equatorial Pacific Ocean in recent months. This indicates that ENSO-neutral conditions have settled in for at least the short term. In addition to SSTs, the NOAA Climate Prediction Center (NOAA-CPC) reports the upper- and lower-level wind patterns are back to average levels, consistent with ENSO-neutral conditions. Moreover, the Southern Oscillation Index between October and December, a measure of sea level pressure, is also average, which signifies that the atmosphere and sea surface are in concert (Figure 13a).
ENSO-neutral conditions are expected to remain in place for at least the next several months. Official forecasts issued jointly in mid-January by NOAA-CPC and the International Research Institute for Climate and Society (IRI) indicate a 97 percent probability of ENSO-neutral conditions continuing through the January–March period (Figure 13b). The probability for neutral conditions remains greater than 80 percent through May. After May, confidence in ENSO forecasts is lower. However, for longer-term outlooks, neutral conditions still remain most likely.
The absence of strong El Niño or La Niña conditions leaves room for more variable weather patterns across the western U.S., making seasonal forecasting for Arizona and New Mexico more difficult. Nonetheless, current seasonal precipitation forecasts suggest a slight increase in chances for below-average rain and snow.
The first figure shows the standardized three month running average values of the Southern Oscillation Index (SOI) from January 1980 through December 2012. 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 Dubois, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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