Wind “drought” poses problems for US wind turbines

New Scientist : Large areas of the continental US suffered an extended drop in windiness in 2015. Unlike some other recent major weather events, however, this one isn’t associated with the recent El Niño, according to a report by Daran Rife of the energy consultancy firm DNV GL and his colleagues. They say the phenomenon fueling the drought dates back to mid 2013, when a high-pressure ridge formed over the northeastern Pacific Ocean and western half of North America. The ridge may be associated with another periodic variation in winds and sea-surface temperatures called the Pacific Decadal Oscillation. The result has been wind speeds about 20% below normal in the US West in the first half of 2015 and a drop in electricity output from wind farms of 6%, despite a 9% increase in generating capacity. Although the drought has not significantly impacted wind power investment, it could continue through 2016.