The European Seasonal Forecast System 5 (SEAS5) forecasts above average precipitation across California for the month of January.
The Sacramento Bee, ECMWF SEAS5
As El Niño breaks news records one week after the next, a new suite of data points to a wetter winter for the entire state of California, even wetter than previously thought.
New this week, two new runs of climate model products have been released, and both point to rain and snow on the way. The National Multimodel Ensemble (NMME), which we highlighted as one of the leading signs of a wet winter earlier this week, and the European Seasonal Forecasting System 5 (SEAS5), which has been shown to be more accurate than others across the western United States.
The sign is pretty unambiguous, rain is coming, and in some places quite a lot more.
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Forecast percent above average winter precipitation (SEAS5). The Sacramento Bee, ECMWF SEAS5 .png "precip_pct_djf_nmme_oct_ca (1).png")
Forecast percent above average winter precipitation (NMME). The Sacramento Bee, NOAA CPC NMME
Most of the state, and the vast majority of populated areas, looks primed for rainfall of at least 150% of normal throughout the winter months, with some areas likely receiving double their winter average along the coast, where El Niño is already expected to raise sea levels thanks to warmer ocean temperatures and an ongoing marine heat wave.
This isn’t just limited to Southern California either. The strongest rainfall signal extends from Sacramento and the Bay Area south to San Diego, with the larger above average signal extending statewide and into Nevada and southern Oregon.
The numbers become even more stark when considering what “normal” is for any location. Consider, Sacramento typically sees about 11 inches of rain across December, January, and February. The data here point to this winter being 16–18 inches. San Francisco normally sees 15 inches and this winter would see 24–28 inches. Fresno is typically much drier at 5.5 inches, but here would close in at 9 inches. Farther south, Los Angeles and San Luis Obispo each see about 10 inches during any given winter. This data would about double that — 20 inches.
The most intense raw amounts look to be along the mountains of the north coast, where warm coastal water collides with steep terrain. Widespread winter totals over 30 inches are a decent bet here.
Forecast above average winter precipitation (SEAS5). The Sacramento Bee, ECMWF SEAS5 
Forecast above average winter precipitation (NMME). The Sacramento Bee, NOAA CPC NMME
Of course, reality is never exactly like what a climate model describes. Climate models look at trends across the entire globe. Not on any given hour or day, but across weeks and months to pinpoint overall patterns. They do have real skill, and are not the same as the weather models on your phone that forecast rain.
This means the rain that falls won’t be nearly as smooth. Predicted rainfall will be irregular, characterized by heavy bursts alternating with dry periods rather than a steady, continuous drizzle. Showers and atmospheric rivers will band together to produce more moisture in some areas and less in others. This pattern is likely to be even more pronounced in rugged terrain, where some rain totals could verge on the extreme.
This is a steady increase in the numbers from early August, when rain was looking elevated statewide, but not to the degree predicted for some areas which could see more than double the typical winter rainfall.
Mountain snow also looking heavy, especially in January
Despite a warmer than expected winter from El Niño, snow will still fall at elevation.
Fitting the new European climate data to terrain, a clear picture emerges: a bit less snow in the foothills, but significantly more snow at elevation. This is especially true for the Klamath Mountains and the Sierra.
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Forecast above or below average winter snowfall (SEAS5). The Sacramento Bee, ECMWF SEAS5
Just as with the rain, the snowfall will not be smooth. Expect this trend to be potentially greatly amplified along mountain peaks and ridges, even for portions of Southern California.
The strongest month for both rain and snow statewide is undoubtedly January.
El Niño still not slowing down, and may linger longer
The latest European climate data shows a troubling sign, El Niño could last longer than anticipated.
Earlier estimates put the peak of El Niño’s warmth in November, but a picture of a longer lasting event is emerging that shows the peak coming later in December, with irregular periods of warmth lingering into March and realistically into April and May. That is likely to stretch the wet pattern into the spring.
The European SEAS5 climate model points to an event peaking later and stronger in December, with the effects on California’s weather likely lingering into the spring. The Sacramento Bee
This El Niño is already the strongest and most east-based event of its kind on record at this point in the year, both factors are strong predictors for increased rainfall across California and the southeastern United States.
The next run of these climate products is not until November, at which point El Niño’s rains may already be starting to sneak into southern California.
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Sean Macaday covers the weather for McClatchy Media in California. Originally from Chicago, Sean worked 6 years covering the weather on local television in Minnesota. He holds a bachelor’s degree in meteorology and marine science from the University of Miami.