In fact, some of the wettest and driest winters occur during La Nada periods, according to Patzert.
"Neutral infers something benign, but in fact if you look at these La Nada years when neither El Niño nor La Niña are present, they can be the most volatile and punishing. As an example, the continuing, deepening drought in the American West is far from ‘neutral,'" he said a week ago, we the conditions developed for the Colorado floods.
Is it because wildfires destroyed nearby forests?
This would seem logical, since there are giant burn scars and exposed soil after this and other summer's fires in mountains above Boulder and other communities along the base of the mountains. All that rain falling on the exposed ground, where forests used to be must be part of the problem, right? Well, sort of.
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"Many, many watersheds that were not burned, flooded," said John Moody, a research hydrologist for the U.S. Geological Survey in Boulder who has studied how water runs off land that has recently burned. "In this case of extreme rainfall, three-year old burns probably only contributed a small increment to the total discharge."