The conditions in the tropical areas of the Pacific Ocean are gearing towards the end to one of the strongest El Niño periods in decades and the start of a La Niña cycle.
Climatologists at NOAA expect La Niña to kick in and shift global climate and weather patterns. The El Niño in the Pacific has quickly weakened in recent weeks, and it is expected that neutral conditions will arrive by early this summer, eventually transitioning to La Niña in the fall months.
“Nearly all models predict further weakening of El Niño, with a transition to ENSO-neutral likely during late spring or early summer 2016,” reads a bulletin by NOAA. “Then, the chance of La Niña increases during the late summer or early fall. The official forecast is consistent with the model forecasts, also supported by a historical tendency for La Niña to follow strong El Niño events.”
Within the Pacific Northwest of North America, El Niño typically brings above seasonally warm and dry conditions, but La Niña ushers in the opposite – cold and wetter conditions. The chance of winter snow in the Lower Mainland increases with a La Niña phenomenon.
El Niño is fuelled by the expansion of the equatorial Pacific’s warm body of water off the coast of South America, which reduces the upwelling of cold water and induces warmer and drier weather. The so-called Walker Circulation that moves water and air heated by the sun to the west through easterly trade winds slows down.
In contrast, a La Niña period occurs when this circulation accelerates. Warm water in the equatorial Pacific is much farther west than usual, allowing colder waters to drive weather patterns.
El Niño conditions in B.C. decimated the 2014/2015 winter ski and snowboard season and there were predictions last summer that warm and dry conditions would continue and worsen throughout the 2015/2016 winter, but that did not materialize. Precipitation and snowpack levels across B.C. were closer to average historic levels over the past winter.
This past El Niño period ranks as one of the top three strongest ever recorded. The last extreme El Niño event was in 1997/1998 while the 2009/2010 event that hampered Cypress Mountain’s Winter Olympic skiing and snowboarding competitions was deemed as a moderate event.