The basic reasoning behind arguing that we're headed for another very large el Nino in the not too distant future is pretty persuasive, though.
ftp://ftp.giss.nasa.gov/outgoing/JEH/bams_29mar20062_all.pdf
("Spotlight on Global Temperature" by James Hansen, Makiko Sato, Reto Ruedy, Ken Lo, David Lea and Martin Medina-Elizalde) - DRAFT
An excerpt:
In the "normal", La Nina, phase of ENSO the east-to-west trade winds push warm equatorial surface waters far to the west such that some of the warmest SSTs on the planet are located in the West Pacific Warm Pool. In this normal state the thermocline is shallow in the East Pacific near the coast of South America, where upwelling of cold deep water occurs, and deep in the West Pacific (Fig. 2 of Cane 2005). Associated with this tropical SST gradient across the Pacific is a longitudinal circulation pattern in the atmosphere, the Walker Cell, with generally rising motions and heavy rainfall in the West Pacific and sinking motions and drier conditions in the East Pacific. This Walker circulation enhances upwelling in the East Pacific, causing a powerful positive feedback, the Bjerknes (1969) feedback, which tends to maintain the La Nina phase, as the temperature gradient and the resulting higher pressure in the East Pacific support east-to-west trade winds.
This normal state is occasionally upset when, by chance, the east-to-west trade winds slow down, allowing the warm water piled up in the west to slosh back in the direction of South America. If the chance fluctuation is large enough, the Walker circulation breaks down and the Bjerknes feedback loses power. As the east-to-west winds weaken, the Bjerknes feedback works in reverse, and warm waters move more strongly toward South America, reducing the thermocline tilt and cutting off the upwelling of cold water along the South American coast. In this way a classical El Nino is born.
Given the high degree of chaos in weather and climate, there is great variability among El Ninos and some arbitrariness in the definition of when one has occurred. Enough time since the preceding El Nino needs to elapse for the West Pacific to "recharge" with warm water and for the thermocline to regain its strong tilt such that it is deep in the West Pacific and approaches the surface near South America. An El Nino has the best chance of forming in Northern Hemisphere spring, when the Intertropical Convergence Zone (ITCZ) is close to the equator, SST is a maximum, and equatorial upwelling is weakest. Thus, as Mark Cane (priv. comm.) has stated, once the West Pacific is recharged, we can think of Mother Nature as "rolling the dice" each spring to see if there will be an El Nino.
Figure 3a shows global surface temperature in a six-month period (September 1996 through February 1997) preceding the 1997-1998 El Nino (Fig. 3b). The temperature pattern in the equatorial Pacific region in September 2005 through February 2006 (Fig. 3c) is nearly identical to that of nine years earlier. Subsurface temperatures are now "recharged", i.e., the ocean is ready to launch the next El Nino (http://www.pmel.noaa.gov/tao/realtime.html).
Figure 3d, the temperature anomaly for the most recent month (February 2006), shows that a substantial warm SST anomaly has appeared near South America, comparable in strength to the warm anomaly that appeared in March 1997. Coupled with the movement of the cool anomaly across the date line (Fig. 3d), the temperature gradient along the equator is now such that it should weaken the Walker Circulation and the Bjerknes feedback. Thus we suggest that there is a high probability that an El Nino will develop in 2006. Warm anomalies near Peru are not uncommon in La Nina years, but this anomaly is already substantial in February.
Here is the referenced "Figure 3"
Basically I think that next year will be the El Nino not this one...
