California’s Next Chance of Rain

Monday, 160215, 2200 PST———

Tonight, as Storm 46 heads across Washington State (WA) at a fast clip,  and is well inland by morning, barely grazing California’s far north, the next storm, Storm 47, is coming to life in the mid-Pacific.

Tomorrow, a polar cyclone (low pressure) southwest of the Storm 46 polar cyclone off the coast of British Columbia, spins counter-clockwise as cyclones do in the Northern Hemisphere, blasting cold air from north of its center to south of its center, creating a mid-ocean gale, while on the east side of the cyclone, a flow of warm, moist subtropical marine air gets pulled towards the cyclonic core. Where the two air masses rub each other along the way is a cold front, which takes a curving spiral path.

storm-47-1.jpg
Tuesday 160216 Forecast – Ocean Prediction Center

On Wednesday, the gale pushes the front southeast towards California while the bands of moist air  east of the front travel northeast towards California, bringing rain and snowfall over California ahead of the front when the moisture encounters increasingly unstable conditions that cause it to lift upwards, become cooler, hit dewpoint, form clouds and release precipitation.

Storm-47-2.jpg
Wednesday 160217 Forecast – Ocean Prediction Center

By Thursday, the major rain bands have crossed California, but over California is the most unstable atmosphere, in which convection clouds that cause hail and lightning form. Eventually the cold air front arrives, clearing away all the moisture. Storm over.

Storm-47-4
Thursday 160218 Forecast – Ocean Prediction Center

On Friday, dry conditions are back. How long until the next rain and snow is apparently unguessable right now. I can see why – the Jet Stream meanders all over the place on the model prediction.

JetStream160219
San Francisco State University GFS Model prediction for the Jet Stream on Friday, 160219.

As the eastern Pacific jet continues to break apart and reform repeatedly, it seems anyone’s guess how significant the precipitation for the rest of the wet season will be.

This has been an El Niño where most of the energy has happened offshore, in the western and central Pacific. This has resulted in very high surf during the winter along the West Coast, which is typical of an El Niño, but not the 250% of normal precipitation.

California precipitation has been above average in the north and below average in the south, below average in the coastal Central, and above average in the inland Central. Bottom line, a big El Niño for California it has not been, except for surfers riding all those amazing waves. A big El Niño typically brings 200-250% of average precipitation to SoCal and CenCal.

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