Last week, Los Angeles County dams and spreading ground captured 1.8 billion gallons of water, enough to meet the needs of 44,000 people in one year. That's a relative drop in the multi-year drought bucket, but a start.
While this all sounds like good news, more flooding, rock/mudslides, debris flows and even damaging winds are possible with this upcoming storm. The National Weather Service in Monterey, California, said Monday that this storm is "expected to be one of the strongest storms in terms of wind and rain intensity" since storms in October 2009 and January 2008.
Setup: An Atmospheric River
What has finally opened the door to drought relief in California?
Last winter, the Pacific jet stream was diverted well to the north of the U.S. West Coast by blocking high pressure in the upper-levels of the atmosphere.
(MORE: 2013 Was California's Record Driest Year)
Now, an energetic Pacific jet stream will point squarely over the West Coast this week. This Pacific jet will tap a narrow, deep plume of tropical moisture over 3,000 miles long known as an atmospheric river.
According to NOAA's Earth System Research Laboratory, these atmospheric rivers (ARs) are important:
- About 30-50 percent of annual precipitation in the West Coast states occurs in just a few AR events.
- The strongest ARs can transport as water vapor up to 15 times the average flow of liquid water at the mouth of the Mississippi River, triggering flooding when stalling or making landfall.
In this case, an AR known as the Pineapple Express, so named due to the origin of the moist plume in the central Pacific Ocean near Hawaii, will slide down the West Coast through the week, wringing out the heaviest rainfall from western Washington to northern California.
http://www.weather.com/forecast/regional/news/california-rain-flood-threat-drought-relief-middec2014
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