Can long anticipated ‘Super El Niño’ save California?

El Niño has officially arrived.

Recent trends in the tropical Pacific are catching the eyes of meteorologists and climate watchers. A long anticipated strong El Niño event finally shows signs of life.

For Minnesota, a strong El Niño favors a mild winter. For drought-stricken California, a strong El Niño next fall and winter could be a historically significant event.

Sea surface temperature (SST) anomalies  in the tropical Pacific show strong warming in recent weeks. There is now an unbroken continuous band of +1C SST anomalies from the western Pacific to the coast of South America.

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The National Oceanic and Atmospheric Administration has recognized the trend (.pdf), increasing the probability this El Niño event will linger this year to 60-70 percent.

ENSO Alert System Status: El Niño Advisory Special Notice:

Synopsis: There is an approximately 70% chance that El Niño will continue through Northern Hemisphere summer 2015, and a greater than 60% chance it will last through autumn.

By the end of March 2015, weak El Niño conditions were reflected by above-average sea surface temperatures (SST) across the equatorial Pacific (Fig. 1), and by the expected tropical atmospheric response.

The latest weekly Niño indices were +1.1°C in the Niño-4 region, +0.7°C in the Niño-3.4 region, and +0.6°C and +1.4°C in the Niño-3 and Niño-1+2 regions, respectively (Fig. 2). Subsurface temperature anomalies increased substantially during the month (Fig. 3) in response to a downwelling oceanic Kelvin wave, which resulted in strong positive subsurface anomalies across most of the Pacific (Fig. 4).

Consistent with ocean-atmosphere coupling, enhanced convection shifted eastward to the central equatorial Pacific (Fig. 5), while low-level westerly wind anomalies continued over the western equatorial Pacific and upper-level easterly wind anomalies continued in the central Pacific.

Also, both the traditional and the equatorial Southern Oscillation Index (EQSOI) remained negative during the month. Collectively, these features reflect weak El Niño conditions. Compared to last month, more models predict El Niño (3-month values of the Niño-3.4 index equal to or greater than 0.5°C) to continue throughout 2015 (Fig. 6).

These forecasts are supported by the increase in subsurface temperatures, enhanced convection over the Date Line, and the increased persistence of low-level westerly wind anomalies. However, model forecast skill tends to be lower during the Northern Hemisphere spring, which limits the forecast probabilities of El Niño through the year.

At this time, there is also considerable uncertainty as to how strong this event may become. In summary, there is an approximately 70% chance that El Niño will continue through the Northern Hemisphere summer 2015, and a greater than 60% chance that it will last through autumn.

Strong El Niño ahead?

There are still questions about the peak magnitude of the still blossoming El Niño event. Many of the forecast models are now pushing the eventual SST average above +2C this fall.

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If the climate model consensus is right, SST's reaching above +2C this fall could bring the strongest El Niño event in 18 years since the El Niño of 1997-98. 

The Super 1997-'98 El Niño event brought the mildest winters on record to Minnesota and much of the Upper Midwest.

It also delivered one of the wettest winters on record to California.

A series of storms pounded the Golden State as a relentless Pineapple Express fed a fire hose of moisture from the tropical Pacific. Some parts of California received well over 20 inches of rain that fall and winter.

Mild Midwest and wet California and Gulf Coast winters are typically favored in strong El Niño years.

Indeed, NOAA's Climate Forecast System is favoring heavy rainfall in California and the southern states this fall.

Some scientists at NASA's Jet Propulsion Laboratory are starting to talk about the coming El Niño as a potential drought buster for California next fall and winter. The long trend of negative Pacific Decadal Oscillation (PDO) phase has shifted into positive territory. That could also help strengthen El Niño this fall.

Will the developing El Niño be enough to end the exceptional drought in California next winter?

Stay tuned.