Once again we dodged a bullet. Tuesday's light snow as seen from Wingra Park. On the far side of Lake Wingra are the trees of the UW Arboretum. Tuesday's snowfall of 4.8" broke a century-old record, but that was a mere statistical fluke, as El Nino focused the fury of Snowpocalypse 2010 south and east of us.
In El Nino years the trade winds weaken over the tropics while the westerly winds and the storm tracks move south. Westerly winds in the western Pacific strengthen the flow of warm water that built up in the western Pacific when the trades were strong, back towards the Americas. This warm water combined with the southerly storm track leads to wet stormy winter weather from California to Texas to the Carolinas.Other factors, most likely including global warming, contributed to the ferocity of the storm in the mid-Atlantic and New England. Interesting discussion here, with lots of striking weather maps and other links.