Cool Pacific Pattern Shaped 2011 Weather Extremes; Heat Dominates U.S. in 2012 In a briefing and several postings today, the National Oceanic and Atmospheric Administration reviewed the most notable climate and weather events of 2011. Many of these events - from an extreme East African drought to Australian deluges - were significantly driven by a "double-dip La Niña" cooling of the tropical Pacific Ocean, agency scientists said. Through the next three months, the agency sees rising odds of the opposite Pacific phenomenon, El Niño, a condition that has markedly different impacts on weather patterns around the world. The agency released its summary of conditions in the United States through the first half of 2012 on Monday, focusing on the record June heat and spreading drought. In a Twitter chat on Wednesday, Deke Arndt, the chairman of the agency's National Climate Extremes Committee, will take questions about recent climate patterns (use the tag #ClimaChat). You can follow the discussion through the @NOAALive Twitter account. Here are the highlights from 2011, condensed into slides: