California drought: High pressure ridge to blame, not likely to change soon

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Weather watchers say there's a slight chance of rain Thursday in Southern California.

If it comes, it'll be the brief exception to an unusually dry winter.

Meteorologists blame a massive ridge of high pressure air that parked over the west this fall and hasn't budged since.

The pattern has been so persistent some are calling it the "ridiculously resilient ridge."

Persistent dryness

Mark Jackson with the National Weather Service says, the high pressure zone essentially acts like a wall that blocks wetter weather from entering the region.

It will occasionally wobble at its edges, allowing rainstorms from the ocean to reach land, but these are usually weaker storms with minimal rain.

Jackson adds that in the past some high pressure zones have lasted long periods of time.

"We're talking multiple years," he said.

California's current dry spell dates back three winters, with 2013 coming in as LA's driest year on record. Water reserves are so low that Governor Jerry Brown issued a drought emergency earlier this month.

Breaking the pattern

Alexander Gershunov with the Scripps Institution of Oceanography says the high pressure ridge is part of a much larger weather pattern currently in play over the  Northern Hemisphere that includes the polar temperatures chilling parts of the Midwest and East Coast.

For things to change, Gershunov pointed out, this bigger system has to "break up and change to a different pattern."

That doesn't seem likely to happen any time soon though.

Gershunov speculates - totally hypothetically - if scientists could inject a Great Lakes-sized amount of cold water into the ocean off the coast of Washington and Oregon, it would possibly alter patterns enough to break up the high pressure ridge.

"I don't know who has a syringe big enough to do that," he said, adding it would be a very bad idea to attempt any such weather manipulation.

"We don't really understand what the unintentional consequences would be."

Perhaps that's why such schemes are usually associated with villains in James Bond movies.

Marty Ralph, also with the Scripps Institution of Oceanography says Thursday's chance of rain could provide some temporary relief though, possibly even doubling the total amount of rain fall so far this season.

"Which isn't saying much because it's been so paltry," he said.

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