La Niña likely to grow stronger this winter
Published: Sunday, Sep. 25, 2011
Long-range weather predictions are notoriously inaccurate. Most weather models will give you predictions out no more than 10 days. However, what if you want guidance for months out?You can turn to the National Oceanographic and Atmospheric Administration, with its predictions about the El Niño/La Niña-Southern Oscillation, or to alternative folk claims of uncertain accuracy.
One of the key influences on our weather is El Niño and its sister, La Niña, which are triggered by changing conditions in the Pacific Ocean. NOAA recently predicted that the current La Niña will continue to strengthen into this winter. This condition produces cooler surface seawater temperatures in the central and eastern equatorial Pacific.
Jan Null, a former National Weather Service lead forecaster and PG&E meteorologist, is recognized as an expert on La Niñas and El Niños and their relationship to California's weather.
According to Null's studies (see his Web page at http://ggweather.com/enso.htm), weak, moderate or strong La Niña periods usually produce below-normal rainfall — typically about 87 percent of normal on the Central Coast, and even less in Southern California as the storm track is shifted northward.
However, last year's La Niña cycle serves as a reminder that not all such events are created equal. Most locations throughout San Luis Obispo County recorded above-normal rainfall. Diablo Canyon had 28 inches, or 118 percent of normal. SLOweather.com in western San Luis Obispo recorded nearly 38 inches of rain, or about 158 percent of normal. Despite the above-average rain last season, the strongest storms with their destructive winds remain mostly north of the county in a classic La Niña fashion.
Because we never had above-normal precipitation from back-to-back La Niña cycles, I believe we will probably have below-normal rainfall this year.
Many folks base their long-range forecasts on strange natural events that seem to correlate with weather changes. For instance, several readers have commented on the early migrations of tarantula spiders in the North County, which may mean a wet winter.
Other cold winter indicators are pigs gathering sticks and heavier coats of fur on animals. A few people have told me that the county's oak trees are overloaded with acorns, which also suggests we are going to have a wet winter. Another source of weather prediction is the Farmers' Almanac. It claims that its longtime weather forecaster, "Caleb Weatherbee," can predict weather 16 months in advance for seven different U.S. climate zones. According to the Farmers' Almanac website, Weatherbee uses a "top secret mathematical and astronomical formula that relies on sunspot activity, tidal action, planetary position and many other factors."
The formula is locked up in a black box, much like the secret recipe for Kentucky Fried Chicken. Quoting the website, "Since 1818, this carefully guarded formula has been passed along from calculator to calculator and has never been revealed."
Many meteorologists are skeptical, but the almanac sells nearly 4 million copies per year and does have a large climate database, so it can be a great tool in knowing when to plant your garden.
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