Weekly NINO3.4 sea surface temperature anomalies (week of September 10) are back above the +0.5 deg C threshold of an El Niño. NINO1+2 sea surface temperature anomalies have dropped recently, but they should rise again as the new downwelling (warm) Rossby wave makes its way east and the warm water is drawn to the surface.
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A map showing the NINO regions is here.
The sea surface temperature anomalies for the NINO3.4 region in the eastern equatorial Pacific (5S-5N, 170E-120E) are a commonly used index for the strength, frequency and duration of El Niño and La Nina events. We keep an eye on the sea surface temperatures there because El Niño and La Niña events are the primary cause of the yearly variations in global sea surface temperatures AND they are the primary cause of the long-term warming of global sea surface temperatures over the past 30 years.
The NINO1+2 region is in the far eastern tropical Pacific, just south and west of the Galapagos Islands. We monitor sea surface temperatures there to see if an El Niño is impacting the eastern equatorial Pacific as well. Those East Pacific El Niños are stronger than its siblings in the Central Pacific.
For more info see the most recent full update The 2014 15 El Niño – Part 16 – September 2014 Update – Still Seeing Mixed Signals.
The Sea Surface Temperature anomaly data used in this post is available through the NOAA NOMADS website (Both NOMAD2 and NOMAD3 websites have been down recently, which leaves us with NOMAD1):