El Niño: Relief or Ravage for the Dry West Coast?

This year may be the strongest El Niño in over fifty years, and we can expect changes to global wind and precipitation patterns. Here on the West Coast, where drought has led to regional water shortages, there is hope that a wetter winter will provide some relief to the parched landscape. But rather than relief, El Niño may bring chaos to the region; last week rainstorms in southern California created massive mudslides that swept through northern L.A. County and closed regional highways. So will El Niño relieve or ravage the west coast?

Heavy rain in California triggered mudslides October 16, 2015, closing parts of I-5 (http://indefinitelywild.gizmodo.com/inside-californias-disastrous-mudslides-1737348762)

Heavy rain in California triggered mudslides October 16, 2015, closing parts of I-5 (http://indefinitelywild.gizmodo.com/inside-californias-disastrous-mudslides-1737348762).

Wait, wait, wait… remind me what El Niño is again?

El Niño is the warm phase of the El Niño-Southern Oscillation (ENSO), a naturally occurring phenomenon that cyclically affects weather patterns. During El Niño years (every ~2 to 7 years), an ocean-atmosphere interaction leads to warmer ocean temperatures and alters precipitation and temperature patterns. On the West Coast, this means warmer and often drier winters in Oregon and Washington, but much wetter winters in California.

El Niño is predicted to increase precipitation in California from January to March 2016 (http://www.latimes.com/local/lanow/la-me-ln-el-nino-drought-20151016-story.html).

El Niño is predicted to increase precipitation in California from January to March 2016 (http://www.latimes.com/local/lanow/la-me-ln-el-nino-drought-20151016-story.html).

Okay, so will a wet winter relieve the dry west coast??

A wet winter in California sounds helpful for the drought-plagued region. And rainfall from El Niño is expected to help refill reservoirs. However, ~80% of California’s water supply comes from groundwater, which needs to be recharged. If rainfall comes in the form of torrential downpours and flash storms, the ground may not be able to efficiently soak up the water. The warmer temperatures associated with El Niño may also mean less snowpack, which reduces the ability for groundwater recharge. Because of this, experts believe El Niño is unlikely to end California’s drought.

On the upside, warm ocean temperatures mean that Californians may be able to observe the tropical sea snake (look but don’t touch!).

Warm ocean temperatures are bringing tropical sea snakes north to California (Aloaiza / Wikimedia Commons, http://www.iflscience.com/plants-and-animals/el-ni-o-brings-venomous-sea-snakes-california).

Warm ocean temperatures are bringing tropical sea snakes north to California (Aloaiza / Wikimedia Commons, http://www.iflscience.com/plants-and-animals/el-ni-o-brings-venomous-sea-snakes-california).

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