El Niño Helps Fuel String of California Storms

Drought-plagued California is in for considerable rain and snow this week as the impacts of one of the strongest El Niños on record begin to be felt. Those much needed rains, however, come with the potential for flooding and debris flows in areas scorched by wildfires.

Unlike earlier storms this season, which mostly affected Northern California, the entire state is expected to see precipitation from a trio of storms moving eastward across the Pacific Ocean, guided by a strong jet stream.

The first storm was set to move through Monday, followed by the second on Monday evening into Tuesday and then a third on Wednesday.

Successive train of storms expected over the next two weeks in California. El Niño is expected to bringing heavy precipitation to the whole state.

Credit: Weather.cod.edu

“We’re in one of those patterns where we have an active Pacific jet” continually bringing systems in, National Weather Service meteorologist Andrew Orrison said.

While every weather situation has multiple causes, a strong El Niño is “absolutely influencing” the current situation, he said, as it tends to bring wetter, cooler weather to the southern tier of the U.S., including Southern California.

Other, natural climate cycles, such as the Arctic Oscillation, are also playing a role in this particular weather setup, California state climatologist Mike Anderson said in an email.

While it is unclear how those factors might shift as the season progresses, the wetter California weather is favored to hold for the next few weeks — as well as the season as a whole — because of El Niño’s influence, Mike Halpert, deputy director of NOAA’s Climate Prediction Center, said in an email.

That is welcome news in a state that has spent four years mired in a record-breaking drought after successive winters where storms were largely kept away and the snowpack melted out early thanks to record-warm temperatures.  

With these storms, rains will fall in coastal and inland areas, while snows will fall in the inland mountain ranges, particularly in the southern Sierra Nevada.

The storms so far this season have mainly benefited the northern reaches of the mountain range, which is measuring an about-average snowpack so far this year. These latest storms could bring some particularly heavy snowfalls to the southern Sierras, possibly up to 2 feet.

Locally heavy amounts of rain are possible and could lead to flash flooding. Concerns for floods and debris flows are particularly high in the coastal areas of Southern California where wildfires have left behind burn scars devoid of rain-trapping vegetation.

“So when it rains hard, there’s not really much to stop it,” Orrison said.

While the rains are overall a welcome sight, they will only put a small dent in the ongoing drought because of the sheer magnitude of precipitation California has missed out on in recent years — about a year’s worth from 2012 to 2014, according to one estimate.

To make up that deficit and replenish reservoir and groundwater supplies will take many more storms and likely several years, experts have said.