Weather Watch

La Niña likely to grow stronger this winter

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.

This week’s forecast

A Pacific weather system will cross Northern California today and will produce extensive coastal low clouds, fog and drizzle this morning throughout San Luis Obispo County.

The North County will have clear to partly cloudy skies by this afternoon. However, the beaches and the coastal valleys will see mostly overcast to partly cloudy skies for most of the day.

Maximum temperatures today should range from the low to mid-60s along the beaches. The coastal valleys should range from the high 60s to the low 70s, while the North County will only reach the low 80s.

This August and September have seen extensive drizzle along the beaches, especially the northwesterly facing beaches of Morro Bay, Los Osos and Montaña De Oro.

The SLOWeather.com weather reporting station in Baywood Park has recorded 0.18 inches of precipitation from fog and drizzle this season.

A trough of low pressure will pass over the Central Coast tonight into Monday morning and will produce a steep pressure gradient along the coastline.

This gradient will give strong to gale force (25- to 39-mph) northwesterly winds along the coastline and a greater amount of sunshine along the beaches Monday.

Fair skies and warmer temperatures are on tap for Tuesday, then warm temperatures Tuesday through Thursday as a high pressure ridge builds across California and a northerly (offshore) flow develops.

Sunny and warm beach weather, along with a high northwesterly swell is expected Wednesday.

Cooler temperatures are expected later this week with another round of increasing clouds and areas of drizzle next weekend.

The remnants of Hurricane Hillary could produce another round of thunderstorms by the first part of October.

Surf and sea report

Arriving from the Northwest:

Today’s 3- to 5-foot northwesterly (290-degree deep-water) swell (with an 8- to 11-second period) will remain at this height and period through Monday morning.

Strong to gale force (25- to 38-mph) northwesterly winds will produce a 4- to 6-foot northwesterly (310-degree deep-water) sea and swell (with a 4- to 11-second period) Monday afternoon through Tuesday.

A 970-millibar low-pressure system moving into British Columbia with hurricane-force winds will produce a 7- to 9-foot northwesterly (290-degree deep-water) swell (with an 8- to 15-second period) along our coastline Wednesday, decreasing to 5 to 7 feet Thursday.

This swell will further lower to 4 to 6 feet (with an 8- to 11-second period) Friday.

Arriving from the Southern Hemisphere:

A large storm is expected to develop off the coast of New Zealand next week. If this storm develops as advertised, another Southern Hemisphere swell should arrive along our coastline by Oct. 4.

Seawater temperatures:

They’ll range between 58 and 61 degrees through Monday, decreasing to 57 and 60 degrees Tuesday, and will remain at this level through Friday.

Pastor Doug’s passing

Our dear friend Doug Carroll lost his epic battle with multiple sclerosis last week.

Pastor Doug, you were a greater shepherd than most ever realized.

If you have any questions or comments about weather or this column, I would love to hear from you. Please write to me at PGEweather@pge.com.

John Lindsey, media relations representative for PG&E and local weather expert, has lived on the Central Coast for more than 25 years. To subscribe to his daily weather forecast or ask him a question, email him at pgeweather@pge.com.

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