This gigantic mass of water, with its strong winds and powerful currents, profoundly influences our weather and climate.
As the temperatures and currents of the Pacific change, so does our Central Coast weather.As I mentioned in last week's column, the National Oceanic and Atmospheric Administration's Climate Prediction Center in Camp Springs, Md., indicated that the current La Niña would peak strongly until next spring.
That will bring cooler surface temperatures to seawater in the central and eastern equatorial Pacific.
Jan Null, a former National Weather Service Lead forecaster and Pacific Gas and Electric Company meteorologist, is recognized as an expert on El Niños and La Niñas and their relationship to California's weather.
According to Null's studies (see his web page at http://ggweather.com/enso.htm), weak and moderate El Niños give average rainfall along the Central Coast.
However, strong El Niño events can produce about 140 percent of above-normal rainfall for our area and even greater amounts in other parts of the state.
In 1982-83, El Niño produced huge ocean swells and periods of intense rain and flooding. There were more than 43 inches of rain at Cal Poly.
Just 15 years later, an even greater El Niño event occurred and produced 44 inches of rain at the Diablo Canyon Power Plant Ocean Lab. Most of these rain events were evenly spaced and created few flooding problems.
On the other side of the coin, however, La Niña periods usually produce below-normal rainfall, on average about 87 percent of normal on the Central Coast, and even less in Southern California as the storm track is shifted northward.
This La Niña condition can be amplified or reduced by another large-scale ocean water temperature cycle called the Pacific Decadal Oscillation, or PDO.
The PDO is found primarily in the North Pacific. The phases of the PDO are called warm phases or cool phases.
Unlike El Niño and La Niña, the PDO stays in one phase for a lot longer — between 10 and 40 years. The El Niño and La Niña phases usually last for about a year or so.
It appears that we are still in the cool phase of the PDO, which should increase the La Niña effect and produce a greater chance of below-normal rainfall.
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