Weather Watch

Wind offers lesson in renewable energy

More than 1,200 fourth- grade children throughout San Luis Obispo County will have the opportunity to attend the San Luis Obispo Farm Bureau’s Great Ag Adventure at the Paso Robles Event Center on Wednesday, during National 4-H Week.

This event allows students to explore different aspects of agriculture in San Luis Obispo County. Each year, volunteers from the local farm community share their expertise with students by providing different demonstrations. This year’s science experiment will be “Wired for Wind,” which will introduce students to the possibilities of using wind as one source of clean and renewable energy.

Farmers and ranchers have been harnessing the wind for centuries. Windmills were first used to grind grains and produce flour for baking bread. Those windmills were later modified to run water pumps and eventually to generate electricity. Today, modern windmills called wind turbines generate large quantities of electricity.

According to the California Energy Commission website, there are more than 13,000 utility-scale wind turbines in California. About 95 percent of these are located in three primary regions: Altamont Pass in the eastern Bay Area, Tehachapi near Bakersfield and San Gorgonio near Palm Springs. All of these sites have yearly average wind speeds of more than 12 mph. Additionally, many farms and ranchers are using smaller wind turbines to produce electricity.

If you’re planning to install a wind turbine to produce electricity, you need hourly wind speeds of at least 12 mph for six hours a day.

A precise understanding of wind resources at your location is critical.

Wind speeds in San Luis Obispo County vary greatly from one location to another. Wind speeds also change from season to season and even from hour to hour. For example, as the inland warms during the day, so does the air directly above it. As this warm air rises, cooler air from over the Pacific rushes through the coastal valleys and passes toward the interior during afternoon hours to fill this void. At night, the land cools more rapidly than the water and the winds rapidly decrease.

At the Diablo Canyon meteorological tower, the strongest winds occurred during April at the zenith of the northwesterly (onshore) spring winds. The month with the least winds is November. The windiest time of the day is 5 p.m. and the winds are calmest at 7 a.m.

If you’re curious about wind resource at your home, you can review existing wind maps at the Department of Energy website at www.windpoweringamerica.gov/wind_maps.asp.

However, the best method of determining average wind speed at your location is to install an anemometer (a device that measures wind speed) on a tower at the height you plan to install your wind turbine.

Weather forecast

Mostly clear and dry weather, except for a few areas of morning low clouds along the beaches, will continue through tonight.

Today’s temperatures will range from the low to mid-70 along the southwesterly beaches (Cayucos, Avila Beach and Shell Beach). The westerly facing beaches (Pismo Beach and Oceano) will be a little cooler, ranging from the high 60s to low 70s, while the northwesterly facing beaches (Cambria, Morro Bay, Los Osos, Montaña De Oro and Nipomo Mesa) will range from the mid- to high 60s.

The coastal valleys (San Luis Obispo) and will reach the mid-70s, while the North County (Paso Robles) will hit the low to mid-80s today.

We are still on track for cool and wet weather this week, with rain first arriving in Northern California tonight before spreading southward toward the Central Coast.

The first cold front will weaken as it moves down the coastline Monday and is expected to produce heavy drizzle/light rain late Monday night into Tuesday morning.

Unlike the first cold front, the following cold front will intensify due to upper-level support as it moves toward the Central Coast. This vigorous cold front will pass the Central Coast on Wednesday with strong to gale force (25 to 38 mph) southeasterly winds and periods of moderate rain.

Accumulated precipitation should range between 0.25 and 0.75 inches Wednesday.

Even heavier precipitation is forecast across the Sierra with snow above 6,000 and 7,000 feet.

At this time, it appears there will be a return to dry weather with strong to gale-force (25 to 38 mph) northwesterly winds and near normal temperatures Thursday through Friday.

Surf and sea report

Arriving from the Northwest:

Today’s 3- to 5-foot northwesterly (305-degree deep-water) sea and swell (with a 7- to 11-second period) will become a 2- to 4-foot (with an 8- to 10-second period) Monday.

A 5- to 7-foot west-northwesterly (285-degree deep-water) swell (with an 11- to 14-second period) will arrive along the Pecho Coast on Tuesday and remain at this level through Wednesday.

Combined with this west-northwesterly swell will be 4- to 6-foot southerly (195-degree shallow-water) seas Wednesday.

A 988-millibar storm is forecast to move into the Pacific Northwest on Monday. An 8- to 10-foot northwesterly (300-degree deep-water) swell (with an 11- to 15-second period) is expected to arrive along our coastline Thursday, decreasing to 5 to 7 feet Friday.

Combined with this west-northwesterly swell will be 3- to 5-foot northwesterly (310-degree shallow-water) seas Thursday.

Arriving from the Southern Hemisphere:

A large and intense storm developed about 700 miles southeast of New Zealand earlier this week. This storm produced hurricane force winds and southwesterly seas of nearly 45 feet in height.

Southern Hemisphere (210-degree deep-water) swell from this storm can be expected to reach the NOAA SE Hawaii marine buoy stationed about 185 nautical miles southeast of Hilo on Monday.

This buoy will provide a good indication of final swell height and period along the Central Coast a few days later.

If the swell develops as advertised, a 2- to 4-foot Southern Hemisphere (220-degree deep-water) swell (with a 20- to 22-second period) can be expected to arrive along the Central Coast shoreline Wednesday, peaking Thursday at 3 to 5 feet (with an 18- to 20-second period).

Note: A few beaches in Southern California may see wave faces reaching more than 12 feet.

The relaxation the northwesterly winds has produced much warmer seawater temperatures along the Central Coast. The Diablo Canyon waverider buoy is reporting a sea surface temperature of 63.5 degrees.

Seawater temperatures will range between 60 and 63 degrees through Wednesday, decreasing Thursday through Friday.

Open house events

PG&E is inviting the public to attend open houses next week to learn more about the Diablo Canyon Power Plant.

The events take place Thursday in San Luis Obispo from 4 to 6:30 p.m. at the San Luis Obispo Library, 999 Palm Ave., and Saturday in Morro Bay from from 1 to 4 p.m. at the Morro Bay Community Center, 1001 Kennedy Way.

Diablo Canyon employees will discuss a variety of topics, including safety and security, license renewal, emergency preparedness, seismic safety and the economic benefits of the plant. All are welcome and refreshments will be served.

John Lindsey is a media relations and nuclear communications representative for PG&E. He is also a meteorologist who specializes in forecasting for San Luis Obispo County. Send him questions to pgeweather@pge.com.

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