Out of the dryer, into the rinse

jlindsey@thetribunenews.comMarch 31, 2012 

Bob Blanchard of Old Creek Ranch near Cayucos gazed at the dry coastal hillsides this winter with great concern. The Santa Lucia Mountains and Irish Hills took on a bronze hue that looked more like their appearance during summer than the Celtic green normally visible during winter.

“This winter’s dry spell was grim. We were looking at a disaster and trying to figure out how we would keep our herd together this summer.” Blanchard told me.

The Blanchards and many other coastal ranchers were evaluating purchasing feed, selling their cattle or even moving their herds northward along the Oregon coast this summer.

December, January and February, historically our wettest months of the year, only produced a combined total of 2.5 inches of rain this season along the Pecho Coast at Diablo Canyon nuclear power plant. Normally, the rainfall total for that period at the power plant is about 13.5 inches.

This year’s La Niña cycle was partly to blame. La Niña cycles produce stronger-than-normal trade winds across the equatorial Pacific. This condition triggers a greater amount of upwelling along the North and South American Pacific coastlines, which gives rise to cooler surface seawater temperatures.

These cooler waters tend to keep a persistent ridge of high pressure over California that often forces the storm track toward the Pacific Northwest, leaving the Central Coast with less rain.

What a difference a month can make. Thankfully, the ridge of high pressure moved southward and a trough of low pressure parked off the California coast this March and allowed a series of storms to produce much-needed rain.

“The rains over the last two weeks have changed our outlook tremendously” Blanchard said. “When it rains like this in March or April we usually get decent amounts of rye grasses which allow the cattle to flourish.”

This March, about 3 inches of rain fell at Cal Poly, home of climatology for San Luis Obispo. From 1893 through 2012, March averages 3.4 inches of rainfall. In the North County, Paso Robles has seen 2.3 inches of precipitation or about 105 percent of normal.

For San Francisco, which experienced some of the driest Decembers and Februarys on record, March turned out to be the fifth wettest March in 85 years, with almost 6 inches of rain recorded or about 200 percent above average. Farther north, Fort Ross along the Sonoma County coast has recorded a little more than 12 inches of rain this March, normally it receives about 5 inches.

All this late rain could be a good thing for the snowpack. Right now, April snowpack surveys are in progress. On March 1, the statewide snowpack was only about 30 percent of normal. Preliminary data indicate that the snowpack has increased to between 49 and 50 percent of normal. That’s a 20 percent increase in the snowpack in just one month, according to PG&E principal hydrologist Gary Freeman. April 1 is historically considered the maximum point of accumulation for the snowpack, before the longer and drier days start to melt the snow.

This is reminiscent of water conditions in 1991 when a wet March significantly tipped the balance in what would have been one of the driest years on record.

More rain is likely in April. The Climate Prediction Center is predicting this winter’s La Niña will transition to El Niño/La Niña-Southern Oscillation-neutral conditions later this month. This condition will produce an equal chance of normal rainfall during April. Unfortunately, according to Cal Poly rainfall records only about 1.5 inches of rain usually falls in April, as the rain season gradually ends.

As we move into April, recovery from this year’s rainy seasons deficit will be nearly impossible. The wettest April on record at Cal Poly was 1967, which produced 6.9 inches. It would take more than 10 inches to put us at near-normal for the year.

What does the next rainy season hold for Central California? According to experts at NOAA, of all the historical two-year La Niña events between 1900 and 2009, 60 percent of those events transitioned to El Niño conditions in the tropics during the following winter season. Additionally, climate models are indicating an El Niño condition developing late this year, which normally produces average or above average rainfall along the Central Coast. So, the trends seem to indicate that we’ll see normal to slightly above-normal precipitation here next winter.

Today’s forecast

This morning will start out partly cloudy but dry as fresh to strong (19- to 31-mph) northerly winds sweep over San Luis Obispo County. Fresh gale- to moderate gale-force (32- to 46-mph) northwesterly winds will develop along the coast this afternoon, decreasing tonight.

Fresh to strong (19- to 31-mph) northeasterly (offshore) winds Monday will produce clear skies and warmer weather with many locations reaching the low 70s.

Moderate to fresh (13- to 24-mph) northwesterly (onshore) winds along with night and morning low clouds and fog will develop Tuesday.

A classic spring type of weather pattern with the Eastern Pacific High stationed off the coast will produce strong to gale force (25- to 38-mph) northwesterly winds Wednesday through Friday. These onshore winds will allow night and morning low clouds and fog to develop during this time.

Today’s surf report The highest waves since January 2010 are arriving along the San Luis Obispo County coast this morning.

A 978-millibar (28.86 in/Hg) storm off the Northern California coast combined with a 1,031-millibar Eastern Pacific High about 700 miles to the southwest of this intense low-pressure system produced a 800-mile west-northwesterly fetch (distance of water over which the wind blows) about 600 miles west-northwest of Diablo Canyon on Saturday. West-northwesterly winds in this fetch have reached near hurricane-force levels.

This west-northwesterly swell generated by the storm reached 33 feet at the NOAA California Marine Buoy (Station 46059) 357 miles west of San Francisco Saturday.

This west-northwesterly (283-degree deep-water) swell is arriving this morning at 16 to 18 feet (with a 14- to 17-second period). The projected peak of this swell is expected to occur between 5 and 9 a.m. today.

Note: Wave heights at the NOAA offshore marine buoys will reach more than 24 feet during this period. If you’re planning to watch these large waves, please practice a great deal of caution and never turn your back to the ocean. Remember, individual waves can be nearly twice as high as what is being reported by the marine buoys.

This west-northwesterly swell will gradually decrease this afternoon to 13 to 15 feet (with a 7- to 15-second period), further lowering to 12 to 14 feet by tonight.

A 10- to 12-foot (300-degree deep-water) northwesterly swell with an 11- to 14-second period) is forecast Monday, decreasing to 5 to 7 feet (with an 11- to 13-second period) Tuesday.

A 7- to 9-foot northwesterly (320-degree deep-water) sea and swell (with a 5- to 12-second period) is forecast Wednesday and will remain at this height and period through Friday.

Arriving from the Southern Hemisphere: Today’s 2- to 3-foot Southern Hemisphere (200-degree deep-water) swell (with a 15- to 17-second period) will continue at this height and period through tonight.

• • •

Join PG&E employees April 14 to celebrate Earth Day at Montaña de Oro State Park. The event is sponsored by PG&E and the California State Parks Foundation. Please register at the California State Parks Foundation website, www.calparks.org/ programs/earth-day/

Be sure to dress for outdoor work with long pants, long-sleeved shirts, sturdy shoes, hats, gloves and sunscreen. Snacks and lunch will be provided. Bring your own refillable water bottle. Rangers will provide tools and supervision.

John Lindsey is a media relations representative for PG&E. He is also a local weather expert and has lived along the Central Coast for more than 25 years. If you would like to subscribe to his daily weather forecast or ask him a question, send him an email at pgeweather@pge.com.

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