Weather Watch

El Nino's late arrival may bring average rainfall

The El Niño/Southern Oscillation (ENSO) can have a profound effect on our local weather. Since April 2010, this cycle has either been in a La Niña or neutral condition that has probably contributed to California’s severe drought.

Predictions back in July 2014 indicated a 70 percent chance of a weak to moderate El Niño onset last August, and an 80 percent chance that it would occur by November.

Unfortunately, it didn’t happen until last month when a weak El Niño condition developed, according to the National Oceanic and Atmospheric Administration’s Climate Prediction Center (CPC).

As I’ve written before, the primary driver of “ENSO” (pronounced “en-so”) are sea surface temperature anomalies across the western and central equatorial Pacific. However, this cycle is an interplay between the ocean and atmosphere. In other words, before a weak, moderate or strong El Niño is declared, the atmosphere must show signs that it is responding to above normal sea surface temperatures.

In February, the atmosphere finally responded to the relatively warm seawater temperatures with increasing low-level westerly winds over the equatorial Pacific and enhanced rainfall over the western equatorial Pacific. Thus, the Climate Prediction Center declare a weak borderline El Niño last week.

So what does this mean for Central Coast rainfall?

Jan Null, a former National Weather Service lead forecaster and PG&E meteorologist, is recognized as an expert on El Niños and La Niñas and their relationship to California’s weather. According to Null’s studies, weak and moderate El Niños give near average rainfall along the Central Coast. However, strong El Niño events can produce about 140 percent of above-normal rainfall for our area. 

But here’s the problem, El Niño conditions at this time of year — March, April and May — has only produced above average rainfall in three of the last 10 El Niño years or about 30 percent of the time. It just may be too little, too late.

Currently, the CPC is advertising a 50-60 percent chance that El Niño conditions will continue through the Northern Hemisphere into this summer. In fact, the climate models are indicating that El Niño conditions could continue into next winter. Historically, the ENSO has been notoriously difficult to project.

Nevertheless, we can say that El Niño has finally arrived.

If you would like to learn more about El Niño, and its sister, La Niña, which are triggered by changing conditions in the Pacific Ocean, I will give a presentation at the Central Coast Aquarium at the “Sharks After Dark: Lecture Series” at 7 p.m. March 27.

Spend an evening exploring the Aquarium after hours, enjoying drinks and appetizers. Tickets are $20 at the door and space is limited. RSVP by March 20 by emailing Taylor@CentralCoastAquarium.com or calling (805) 595-7280. Proceeds will support the Central Coast Aquarium’s mission to cultivate a community dedicated to ocean stewardship. ** Safety is at the heart of everything that PG&E employees do. To learn about electric and gas safety to protect yourself and your family, please visit www.pge.com/safety.

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