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El Niño May Be Juicing SoCal’s First Atmospheric River Of The Rainy Season
Anywhere from 1 to 5 inches of precipitation could fall across Southern California this week, as we get hit by our first atmospheric river in some time.
The storm's showing up about three weeks before our expected rainy season. Rains shouldn't be that intense, but residents should be on the lookout for the typical hazards that can pop up, as isolated, heavy pockets of rain can result in debris flows and obstructions on canyon roads.
El Niño’s influence
A strong El Niño is likely exerting some level of influence on the storm, according to Marty Ralph, director of the Center for Western Weather And Water Extremes at the Scripps Institution of Oceanography.
The climate pattern results in warmer ocean temperatures, which can influence storm tracks and help strengthen storms.
“When a storm like the one that’s in the forecast now enters the area between California and Hawaii, it has the potential to have more water vapor in it, because the ocean can evaporate more water into the atmosphere when the sea surface temperatures are warm,” said Ralph.
“By having more water vapor it’s possible for the atmosphere to produce more rain or snow in the higher mountains. And because water vapor is the fuel of the atmospheric river, it has the fuel to strengthen the atmospheric river, essentially.”
An end to fire season?
This storm doesn’t look like it’ll bring enough rain to put an end to our fire season, according to the National Weather Service in Oxnard. They typically look for 3 to 5 inches of widespread, across-the-region rainfall before they can call it.
That said, fire and weather agencies will have a better idea of where things stand after the storm, because then they'll be able to assess where soil, live and dead fuel moistures stand.
Dead fuel is quick to dry out with Santa Ana winds, which peak between December and February. If we don’t get any additional rain (as has happened in recent years) for much of winter, expect fire risk to rise again.