One of the strongest El Niño weather systems in recorded history is forecast to bring warm, dry weather to Washington State this fall and winter, leading to a possible repeat of last summer’s drought.

The El Niño Southern Oscillation (ENSO) is a pattern that causes sea surface temperatures in the Pacific Ocean to fluctuate between warm and cold.

The warming phase–called El Niño–pushes warm water towards the western coast of the United States, while the cooling phase–La Niña–moves water back towards Southern Asia.

Essentially, ENSO’s behavior turns the Pacific Ocean into a large, swirling, bathtub, filled with both warm and cold water.

“El Niño happens about every five years or so when the trade winds–which normally blow from north east and south east at the equator–weaken,” said Biology professor Clay Arrango. “When they weaken, all the warm water that was pushed up towards the western pacific actually sloshes back towards the eastern pacific.”

The sloshing of warm water towards the west coast causes the Pacific Northwest to experience a relatively mild winter during El Niño years.

“We typically get a dryer year with less snow pack,” said Arrango. “Whatever precipitation we do get is likely to fall as rain, but it’s probably not going to be a lot.”

This comes as bad news for the state’s water reservoirs which replenish themselves primarily with snow melt.

After the Cascade Mountains received record-low snowfall last winter, the state’s water supply dried up alarmingly fast. In response,Governor Jay Inslee to declare a statewide drought emergency.

If El Niño forecasts are correct, ski resorts, farmers, and fishermen alike can all plan on struggling through another business year of water shortage.

“Having this El Niño come on the tail end of a prior drought is the worst thing for our region,” Arrango said.

The timing of this upcoming El Nino adds even more stress on Washington’s agricultural sector which is dependent on a sufficient water supply.

The Yakima River Basin is one of the state’s most valuable economic drivers. Serving as the nation’s top supplier of apples and hops, the region exports over $1.8 billion in farm products annually, all nourished by Yakima’s water.

Timothy Hay farmers in Ellensburg can also expect another tough season due to El Niño.

During last summer’s drought, junior water rights owners had their flows reduced to 46 percent of their normal allocation. The current projections for this summer say those same flows could be reduced even further, all the way down to 36 percent.

While El Niño is expected to bring much needed rains to a parched California, Clay Arrango explained that Washington’s water shortage can only be alleviated by snow.

“The western water infrastructure is set up to catch snow melt that melts in the spring and the summer,” Arrango said. “The problem with getting rain is that it doesn’t sit in the mountains. It just goes down and it fills up [the reservoirs] right away, and then we have to let everything else pass through.”

As global warming continues, El Niño-like winters could eventually become the norm in the pacific northwest.

An inefficient water infrastructure has prompted the state to propose a massive project called the Yakima Basin Integrated Plan (YBIP).

Kittitas County Commissioner District three Obie O’Brien says that one of the projects main priorities is to take advantage of the accumulated rainfall, rather than just snow.

“Since we’re not having as much snow, we need to store the water that falls as rain.” O’Brien said.

The YBIP would also construct a new water reservoir south of Ellensburg, raise dam levels, upgrade irrigation systems, and improve fish passages for salmon and steelheads.

The YBIP would cost $3.8 billion and be completed over a course of 30 years.

“The [YBIP] is vital because agriculture is a major economic driver,” O’Brien said. “We need to accommodate the fact that there’s not enough water during drought years.”