Weather and Natural Disasters

California braces for new 'pineapple express' storm as drought shrinks in state

Traffic is diverted around flooded areas in Mill Valley, Calif. last month.
Eric Risberg | AP

The state's historic drought isn't over but portions of Northern California have seen their parched lands relieved of the worst conditions and now are enjoying rainfall totals that are well above normal for this time of year.

At the same time, a new batch of storms are forecast to drop substantial rainfall and snow starting this weekend and could set the stage to become a drought-buster for other parts of the state. One of the storms is known as the "pineapple express" because it's tropical in origin.

"They are expecting some heavy snow up in the high Sierras," said David Gomberg, a meteorologist with the Oxnard/Los Angeles National Weather Service Office. "That's good news for our water supply."

On Tuesday, the state reported its first official snowpack survey of the season in the Sierra Nevada mountain range. It showed water content of just 53 percent of the early-January average.

That said, there's still enough time to improve the frozen water supply in the Sierras. January, February and March are historically some of the wettest months for the state.

The snowpack supplies about 30 percent of the state's water needs and melts in the spring and sustains the state during the summer when there's typically little to no rainfall.

A much-hyped El Nino last year failed to produce enough precipitation statewide to end the drought although it did leave California in better shape than 2015.

Yet as the state enters its sixth year of drought, the rainfall so far this season seems to be helping mostly Northern California while the central region remains largely under dry conditions. Some of the central areas are agricultural communities where farmland has been left fallow in recent years due to cutbacks in irrigated water.

"At this point it's been Northern California receiving the bulk of the precipitation," said Ted Thomas, spokesman for the California Department of Water Resources in Sacramento.

As of Thursday, San Francisco was at about 130 percent of the historic average rainfall for this time of year and Sacramento was at about 160 percent. Also, there are some communities further north that have seen 170 percent more than normal precipitation for this time of year.

In fact, there's been so much rain that federal and state water projects this week have been conducting controlled releases of water from major reservoirs to make room for the upcoming storm flows. Releases have been done at Folsom Reservoir near Sacramento and at Shasta Reservoir north of Redding, California.

Shasta, the state's largest surface reservoir, this week held 118 percent of its historical average while a year ago it was just 50 percent of its average.

"We're not by any means out of drought conditions," said Thomas. "You could say we're doing better."

Indeed, the latest U.S. Drought Monitor released Thursday shows large swaths of the north, including portions of San Francisco Bay area, no longer suffering from drought. A year ago portions of the Bay region were still considered in severe drought. Overall, 38 percent of California is currently in what the monitor calls "extreme" or "exceptional drought" while that number a year ago was almost 70 percent.

It's a different story further south in Central and Southern California. Portions of Southern California, including Los Angeles and San Diego, have received above average rainfall this season but remain under some of the Drought Monitor's worst drought conditions.

As of Thursday, downtown LA was about 140 percent more than normal rainfall for this time of year. LA has already received more than double the amount of rainfall it received last year at this point.

"This is a great start but we've seen years where we got a fair amount of precipitation through the end of December then it was almost like nature turned off the spigot," said Devon Upadhyay, manager of the water resource management group at the Metropolitan Water District of Southern California. The agency is a large water wholesaler serving about 19 million people in six counties.

Meantime, forecasters are predicting California will get substantial precipitation starting this weekend by what's called an atmospheric river, or what's known as a "pineapple express" because they often originate off the Hawaiian Islands and draw up moisture from the tropics.

"The 'pineapple express' has been pretty much absent the last five years," said Mark Moede, lead forecaster for the National Weather Service in San Diego. "That's why the drought has been so persistent."

The tropical storm is expected to dump up to 12 to 15 inches of precipitation in some higher elevations, and the forecast is for a colder system to impact California on Tuesday and Wednesday.

Over the decades, there have several times when these "pineapple express" storms have produced costly flooding in the state and led to fatalities as was the case in January 2005. There also were major floods statewide in the 1980s and 1990s from similar tropical storms.

The National Weather Service on Friday issued a flood watch ahead of the approaching storm for portions of Northern California. The agency said already saturated soils could also lead to flash flood conditions of some streams and rivers.