By Michael Beveridge '17

As one of the strongest predicted weather patterns ever recorded gathers in the Pacific Ocean, many people are left wondering: what is the El Niño and why should I care?

El Niño patterns alternate with La Niña patterns which essentially are differential movements in warm waters driven by strengthening or weakening trade winds (pictured above). Nothing in climate ever has a simple explanation, and El Niño weather patterns are no exception. Due to Earth’s shape and variable rotation speeds-wider parts rotate faster-there are wind patterns that prevail across the Earth’s surface; this phenomena is known as the Coriolis Effect.

Pictured to the right in a simplified diagram, are the wind patterns in the Northern Hemisphere. In La Niña years, warm water from the area around Indonesia is blown northwards past Japan where it is eventually caught in a westerly wind that pushes it towards North America. This causes warm and wetter rainy seasons in South Asia and drier, cooler winters in North America. In El Niño years, those winds weaken for some reason, causing warm water to accumulate off the coast of Central and South America. These warm conditions cause the inverse of La Niña years and instead North America has wetter winters. This coming El Niño is predicted to be one of the strongest on record due to the abnormally large, warm mass of water.

So what does this mean for the United States? The Northeast should see some relief from the bitterly cold “Arctic Vortexes” it’s been suffering from the past few years. While this may be a downside for skiing enthusiasts, the wetter conditions will most certainly benefit the western part of the country.

California is suffering from one of the worst droughts in a century and snowpack is at a record low. This weather pattern should bring much needed rain to many parts of the parched state, however, since the ground is so dry, there are concerns as to how much will be absorbed. When the ground gets as dry as it is, the soil loses its ability to absorb moisture as effectively. Not only does this spell trouble for California’s ailing groundwater reserves, but it could also mean damaging flash floods and mudslides as precarious situations become more volatile.

Sources:

http://www.tampabay.com/specials/2010/graphics/la-nina-vs-el-nino/la-nina-vs-el-nino.jpg

http://faculty.washington.edu/kessler/TALKS/ENSO-AMSteachers2.pdf

http://earthguide.ucsd.edu/virtualmuseum/Glossary_Climate/images/ocean_currents_gyres.gif

http://www.scientificamerican.com/article/strong-el-nino-to-usher-in-lots-of-winter-rain/