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Pineapple Express’ Is Bringing Rain To Northern California

Water vapor imagery of the eastern Pacific Ocean showing a large atmospheric ...

Credit: United States Naval Research Laboratory, Monterey

Above: Water vapor imagery of the eastern Pacific Ocean showing a large atmospheric river aimed across California in December 2010.

Heavy precipitation is predicted for Northern California this weekend. But don't expect the so-called "Pineapple Express" to end California's historic drought, say San Diego climate scientists.

This weekend, Scripps Institution of Oceanography sent Marty Ralph on flights straight into an "atmospheric river" over Northern California. Atmospheric rivers are narrow but powerful plumes of moisture. The ones that hit the West Coast tend to originate in Hawaii, hence their fruity nickname. These storms are responsible for delivering a huge amount of California's annual precipitation.

Scripps climate researcher Dan Cayan contributed to the research while staying grounded in La Jolla. He says if we think of normal storms like lawn sprinklers, then atmospheric rivers are more like fire hoses. They can cause floods, but can also replenish drought-stricken regions.

"They carry with them a hazard as well as a water resource," Cayan said. "So we're really interested in understanding them and tracking them."

A river pouring down on California sounds like a good thing in this time of historic drought, right? Well, don't start thanking the rain gods yet, says Cayan.

"It's very unlikely that we're going to be able to achieve the amount of precipitation we need in order to essentially bring us back to normal. You would just need tremendously active and copious rainfall."

Unless many more atmospheric rivers build up soon, we could be experiencing drought until El Nino, which is predicted to hit California late this year.

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