The National Oceanic and Atmospheric Administration has issued a La Nina Watch for the coming fall and winter seasons. Sea-surface temperatures have dropped by several degrees to below-normal levels in the tropical Pacific from the coast of South America to the International Date Line. This cooling of such a large area of ocean water results in lower evaporation rates and fewer thunderstorms which, in turn, affects upper level wind patterns.
Traditionally, there is a statistical correlation between La Nina conditions and colder winters in our region. However, the relationship is not a perfect one. Furthermore, long-range winter predictions in recent years have been muddled by the presence of much warmer than average ocean temperatures in the Bering Sea and the Arctic Ocean. This means that should the La Nina continue to develop, its effect on our upcoming winter is unknown.