The interesting aspect of plotting Nino3.4 from the NOAA database is that one sees right away that the peak in the data from previous El Ninos does indeed lie roughly in the December time frame. This is after all why it is named El Nino in the first place. I'd appreciate it if you could extend the discussion a bit to explain why this peaking occurs at this time. You stated that atmospheric flow is more important in the winter, but why is the heat in the ocean sloshing from west to east at this particular time? Are westerlies more common in the Northern winter? If so, why? In short, what's the physics behind the El Nino name?