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Published August 22, 2012
El Niño Status and ForecastData Source(s): NOAA-Climate Prediction Center (CPC), International Research Institute for Climate and Society (IRI)
An El Niño Watch issued by the NOAA-Climate Prediction Center (NOAA-CPC) remains in effect this month, as warmer-than-average sea surface temperatures (SSTs) were present again this month across the eastern Pacific Ocean, slightly increasing in extent and intensity over the past 30 days. However, atmospheric circulation patterns, including winds along the equator and areas of tropical thunderstorm activity, so far have responded weakly to the shift towards warmer SSTs, slowing the progression of the El Niño event. The Southern Oscillation Index (SOI) increased slightly in the last month and still remains reflective of ENSO-neutral conditions (Figure 14a). NOAA-CPC notes that statistical and dynamical models continue to show an eventual progression towards El Niño conditions in the next month or two. As a result, NOAA-CPC may issue an El Niño Advisory in the next month or two as El Niño conditions strengthen.
Official forecasts issued jointly by NOAA-CPC and the International Research Institute for Climate and Society (IRI) depict a strong chance of El Niño conditions forming in the next several months and likely continuing through the spring season of 2013 (Figure 14b). Most models forecast that the event will be weak to moderate in intensity, with only a couple of dynamical models betting on a strong event forming. Chances are greater than 75 percent that an El Niño will develop in the August–October period and they remain above 70 percent through the December–February period. Seasonal climate forecasts for the upcoming fall and winter seasons pick up on the expectation of an El Niño event and forecast increased chances of above-average precipitation across parts of southern Arizona and New Mexico. However, a wet winter for the Southwest is not a slam dunk. While El Niño events typically favor above-average precipitation, in the past weak to moderate El Niño events have delivered below-average winter precipitation for Arizona and New Mexico. Despite this, seasonal forecasts call for a slightly increased chance of above-average precipitation, especially in the January–March period.Notes:
The first figure shows the standardized three month running average values of the Southern Oscillation Index (SOI) from January 1980 through July 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.
The first figure shows the standardized three month running average values of the Southern Oscillation Index (SOI) from January 1980 through June 2012. The SOI measures the atmospheric response to SST changes across the Pacific Ocean basin. The SOI is str:
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
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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