The Southern Oscillation Index tracks differences in air pressure between the eastern and western sides of the tropical Pacific.

El Niño and La Niña conditions occur when abnormally warm or cool waters accumulate in tropical latitudes of the central and eastern Pacific Ocean. The Oceanic Nino Index is the tool NOAA scienitsts use to watch for these temperature changes. 

Along with ENSO, what other climate patterns might be useful for predicting temperatures and precipitation in the United States?

OLR anomalies in 2012 versus 2014

Where is El Niño?  How is this year different from 2012 when El Niño was predicted, but never arrived?  

CFSv2 ensemble forecast Nino3.4 sea-surface temperature

The chance of an El Nino has dropped to about 65%. What led to this change in the forecast?

How do changes in the equatorial Pacific Ocean impact places much farther away? The answer for the tropics, at least, lies in changes to the equator-wide atmospheric circulation called the Walker Circulation. 

June 2014 SST anomalies

Why hasn't El Niño been declared yet?  The answer might lie in the gradients of sea surface temperatures across the tropical Pacific Ocean.  

This video shows 15 years of data obtained via Polar-orbiting satellites that are able to detect subtle differences in ocean color, allowing scientists to see where there are higher concentrations of phytoplankton - a proxy for the concentration of chlorophyll in the ocean.

Sea surface temperatures are up. So why haven't forecasters declared El Niño conditions? 

This webinar will examine how variations in the tropical Pacific can affect high-latitude regions such as Alaska.

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