First El Niño storms to soak Bay Area all week

A girl holding a Hello Kitty umbrella walks with her guardian near the California Academy of Sciences building in San Francisco, California, on Sunday, Jan. 3, 2016. A girl holding a Hello Kitty umbrella walks with her guardian near the California Academy of Sciences building in San Francisco, California, on Sunday, Jan. 3, 2016. Photo: Connor Radnovich, The Chronicle Buy photo Photo: Connor Radnovich, The Chronicle Image 1 of / 48 Caption Close First El Niño storms to soak Bay Area all week 1 / 48 Back to Gallery

Round one in a series of storms set to soak the Bay Area this week moved into the region Sunday — the first predominant El Niño weather pattern that forecasters have predicted for months.

While the Bay Area has been hit over the past few weeks with several good rain storms from the north, this week’s back-to-back soakings are coming fast across the Pacific Ocean from west to east, an indicator of an El Niño system, said Jan Null, a meteorologist with Golden Gate Weather Services.

“We’re starting to see a hint of what we’ve been talking about for months as far as the potential for a really strong El Niño,” he said. “What we expect to happen, if this holds true, is this will be the predominant pattern for the next few months.”

Some forecast models show up to 15 inches of rain in the next 16 days in drought-parched California’s most desperate areas. The state’s depleted reservoirs will get much-needed recharging this week and hopefully more in the weeks to come, Null said.

The first wave of rain started with light showers Sunday morning before heavier rain was expected to arrive overnight into the Monday morning commute. Forecasters said the rain won’t relent until next weekend.

“What people are going to experience is persistent rainfall for the next couple days and for most of the week,” said Mark Strudley, a hydrologist with the National Weather Service.

The first concentrated pulse of rain was to hit overnight Sunday before tapering off into scattered showers Monday morning. By Tuesday morning, a heavier bout of precipitation will sweep into the region from the Pacific Ocean.

Between Monday and Tuesday morning, forecasters are looking at roughly a half inch of rain on the Peninsula and East Bay. Around a half inch is forecast with each following storm.

The pattern of steady rain turning to scattered showers and then back to steady rain won’t ease until Friday, when Bay Area skies could clear for the weekend, Strudley said.

But it’s tough to gauge whether the rain will even ease as storms continue to build over the western Pacific Ocean.

“With as fast as these storms are coming off the Pacific, a storm leaving off the coast of Asia will be here about Friday,” Null said.

Pacific Ocean temperatures have been rising for months to the highest levels since the strongest El Niño event in modern history in 1997 and 1998. That winter saw torrential downpours, flooding and landslides around much of the state.

Drought watchers and meteorologists are eagerly waiting to see whether this week’s weather continues for the next three months, which has historically happened during strong El Niño years.

In the Sierra, skiers and snowboarders have rejoiced as wave after wave of fresh powder continues to dump on Tahoe’s mountain resorts. This week’s storms should deliver a decent amount of snow to the Sierra, with up to a foot falling in some areas through Tuesday night.

Evan Sernoffsky is a San Francisco Chronicle staff writer. E-mail: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky