Research & Application

Much-needed mountain snow and rain returned to California this winter, but fell short of expectations amid a super El Niño.

The official snow season for California’s Sierra Nevada came to an end at the start of April on a below-normal note and one that AccuWeather Senior Meteorologist Ken Clark called “disappointing.”

The amount of water stored in the snow for the entire mountain chain averaged 14 percent below normal on April 1, according to the California Cooperative Snow Surveys.

The above images, provided by NOAA’s National Operational Hydrologic Remote Sensing Center, show the amount of water stored in the Sierra Nevada on April 2, 2015, (left) and on April 2, 2016 (right).

The northern Sierra fared better than the southern Sierra with the amount of water in the snow averaging only 5 percent below normal, compared to the 27 percent below normal in the south.

“The numbers are not anywhere near what many had wanted going into the winter,” Clark said. “The much-heralded El Niño brought more snow than the previous four years, but that was not hard to accomplish.”

El Niño occurs when ocean water temperatures rise above normal across the central and eastern Pacific Ocean, near the equator, and typically leads to more storms targeting California.

“The snow that falls over the Sierra Nevada in the winter is crucial during the spring and summer as melting snow accounts for roughly 30 percent of California’s water supply,” AccuWeather Meteorologist Brian Lada said.

Outside of the mountains, the northern-third of California benefited from near- to above-normal rainfall this wet season (since October 1). However, rain was held well below normal in Southern California.

Downtown Los Angeles only received 6.59 inches of the 13.54 inches that typically falls.

“That’s not a great deal better off than last year,” Clark said.

The U.S. Drought Monitor reported that 55 percent of California is suffering from extreme to exceptional drought as of March 24. This is a far cry from what some had hoped would be a drought-busting season due to the strong El Niño.

The anticipation of a super El Niño winter raised hopes of substantial rain and mountain snow, but AccuWeather meteorologists cautioned last summer that such a scenario may not unfold.

The storm track into the Northwest this winter allowed Portland, Oregon, to set a new record for the wettest meteorological winter (December to February) with 26.57 inches.

Clark added that the lackluster super El Niño impacts aren’t all bad news.

“The reservoir levels in the big three reservoirs of northern California are far better off to date this year than last.

Frank Gehrke, chief of the California Cooperative Snow Surveys Program for the Department of Water Resources, leaves the snow covered meadow after conducting the snow survey at Phillips Station near Echo Summit, Calif., Wednesday, March 30, 2016. (AP Photo/Rich Pedroncelli)

“This will help some going into the late spring and summer,” Clark said, “But with the great lack of rain in much of central and Southern California, it is highly doubtful water restrictions will be less severe than last year.”

While Californians may have hoped for a season similar to 1997-98 when the last super El Niño occurred, one major factor hindered those chances.

“A lot goes into the forecast,” AccuWeather Meteorologist Ed Vallee said, “and just because it is an El Niño winter does not necessarily result in excessive rainfall for California.”

“Much like AccuWeather meteorologists foresaw last summer, a strongly positive Pacific Decadal Oscillation (PDO) had an influence in the overall weather pattern, preventing this winter from being a repeat of the last super El Niño of 1997-98,” Vallee said.

A strongly positive PDO refers to anomalously warm waters off the west coast of the United States.

“The strong PDO contributed to the overall storm track being over Washington and Oregon instead of California, which was much farther north than what was seen in 1997-98,” Vallee said.

Both Los Angeles and San Francisco received nearly twice the normal rainfall from fall 1997 to spring 1998. February 1998 remains the wettest February on record in downtown Los Angeles with a total of 13.68 inches. That is more than double what the city received so far this rainy season.

Before the drier late spring and summer months take hold, a turn to a wetter weather pattern later this week will give California an opportunity to see reservoir levels rise some and the snowpack in the higher elevations further build.