By Joseph D’Aleo, CCM ICECAP.US
El Nino is still hanging on but likely not for very long. Warmer than normal water can still be seen along the equator in the tropical Pacific. It is even warmer in the sub-tropical North Atlantic because of the suppressed winter jet stream and subtropical high which meant lighter than normal winds and less clouds.
Signs of the demise of the El Nino are numerous. It is likely given the flip of the PDO which favors shorter El Ninos and stronger, more frequent and lengthy La Ninas that a moderate to strong La Nina is next in the cards this year and next.
Notice in the temperature anomaly plot for NINO region 34 (region shown on the CDC map below)
How we are somewhere between 1998’s super El Nino and a cluster of more moderate ones and how they declined quickly by the summer on the graph that follows (enlarged here). Values are given in STD of NINO 34 SSTA.
ENSO models, both dynamical (coupled air and ocean models) and statistical suggest a rapid cooling with all models dropping below threshold El Nino levels by summer (JJA – June-July-August) and perhaps half reaching La Nina values by summer or fall.
In the depth cross section across the entire tropical Pacific that is built from the TAO-Triton buoy data, we can see the warm water in the eastern top water which was 5C above normal has diminished as the water mixes with cooler surface water and the thermocline is lifted. Notice the developing strong cold pool not unlike that in 1998 at 100 meters across most of the Pacific. Notice the amazing cool down of NINO34 in 1998 from May to June in the multiyear graph above.
The El Nino followed two years of La Nina with below normal temperatures in NINO34 and in much of the Pacific leading to below normal ocean heat content in the tropical eastern half of the Pacific. A strong La Nina in 2007/08 was followed by a summer rebound then another dip in January.
We can see in the heat content the last year, a peak last summer a fall decline and then a multi peak winter warming fed by westerly wind bursts this past winter, notice the decline as we started April.
The Southern Oscillation Index which was in positive La Nina territory in 2007/08 and 2008/09 dropped into negative El Nino territory reaching an incredible 8 STS in early 2010. It has rebounded to positive and usually leads the change of ENSO state by a few months given credence to a return of La Nina.
See much more on the possible implications for the summer and following winter (with recognition of the possible influence of the solar and volcano wildcards) here.