Extraordinary storm events last week and during summer offer a glimpse of what we could face on a broader scale during the coming El Niño Winter, state and local officials warned Monday.
"I think we've seen a pretty good hint of what we're likely to see," said Bil Croyle, deputy director of emergency preparedness for California's Department of Water Resources.
Last week, in what has been considered the fourth year of drought, flooding and mud flows trapped hundreds of motorists in northern Los Angeles County and forced the temporary closure of the 5 Freeway through the Tehachapi Mountains. In August, flash flooding west of Desert Center washed out a 10 Freeway bridge.
Pacific Ocean conditions described as El Niño are associated with a greater chance for a wet winter in California, particularly the southern half of the state, but the effect historically is not felt until January and February.
The probability of a strong El Niño continuing through winter is placed at 95 percent by the federal Climate Prediction Center. That is "about as confident as you will ever see in a climate forecast," said the center's Mike Halpert during a webinar Monday morning.
"We could see upward of 200 percent of normal rainfall," Croyle said. "There's going to be those key areas that have been problematic in the past ... but this could be widespread."
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High among concerns for Southern California are developed areas downslope from burn zones. It was the Powerhouse fire two years ago in the Angeles National Forest that left the Elizabeth Lake Road Corridor so vulnerable last week.
Even during the drought, there were mudflows in Ventura County last winter from the Camarillo Springs burn zone. The slopes in Glendora have yet to recover from the Colby Fire a year ago January.
The drought also causes additional concern for area slopes destabilized by dieback of vegetation and fallen trees.
Strong El Niño winters also tend to bring heavy surf and cause flooding along low-lying coastal areas.
Climate scientists recognize six strong El Niño events since the 1950s, said Andrea Bair of the National Weather Service. Effect on ocean temperatures in the equatorial Pacific is how it is measured. By that signal, this El Niño is developing as second only to 1997-98.
Four of the six El Niños were accompanied by significantly more precipitation in Southern California — but two were not, in 1965-66 and 1072-73, Bair said.
At the Monday briefing, officials urged what they called "neighborhood preparedness," encouraging meetings with neighbors to develop plans dealing with localized flooding, wind damage and power outages, as well as arrangements to evacuate.
"Really we want to get into this neighborhood preparedness model," said Jeanne O'Donnell of the Los Angeles County Office of Emergency Management. "We start looking at not just our house, and ourselves and our family, but start looking at where you are ... getting to know your neighbors a little bit more to prevent that isolation effect, to pull in that network and that safety net so that you can really sustain yourself for a while."
As the kick off for "flood preparedness week," Monday's briefing had been scheduled before Thursday's flash flooding. The Department of Water Resources unveiled a new flood preparedness website.
Though El Niño stands ready to be the antithesis of drought — the bane of the Department of Water Resources the past four years — Croyle encouraged Californians to continue practicing water conservation, noting that recovering from so many low-water years will require more than refilling the state's portfolio of reservoirs, most well under half of capacity.