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Atmospheric rivers helping San Diego rainy season

With 3 atmospheric rivers already in the rain barrel, would this next one be considered a drought buster?

SAN DIEGO — San Diego's rainy season is off to a good start thanks to a series of atmospheric rivers according to Alex Tardy who is a meteorologist with the National Weather Service.

"Well, for this year, this is our third. The one in late October was strong for Northern California, weak for us, then there was December 14th and that was strong for Southern California," Tardy said.

Then there was the Christmas storm cycle that brought record-breaking snow to Lake Tahoe. 

So are we seeing more atmospheric rivers happening in California compared to the past? Tardy said the short answer is no.

"We only typically average 3 to 4 a year and maybe 5 or 6 that are weak atmospheric rivers," he said. 

The moisture in them originates in the Intertropical Convergence Zone and plays a key role in California's rainfall totals. 

"The research shows that 50% - 70% of our rain comes from some form of the atmospheric rivers," Tardy said.

For an atmospheric river to happen you need a plume of moisture from the sub-tropics, a slow-moving low pressure to pull it northward and the jet stream to enhance it. When they all come together you can have incredible amounts of rain and snow. 

"If you have an atmospheric river with everything else... it's kind of icing on the cake," Tardy added.

There was a huge episode in 2010 when it rained for three days starting on December 20 in San Diego. Qualcomm Stadium was flooded and the San Diego River was over 14' high. Tardy said that the one in 2010 was pretty rare.

With three atmospheric rivers already in the rain barrel, would this be considered a drought buster?

"With recent winters since 2000, I would hesitate to call it a drought buster. Most of our rain come in January and February and if we go dry, which could happen in a La Nina year," Tardy said. "I would like to see average at least in January and February before we can say drought buster."

WATCH RELATED: Will the December snow and rain help CA drought? (Dec 2021)

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