Where's the rain? 2013 is third-driest on record for SLO County

pgeweather@pge.comMarch 23, 2013 

Countless cold fronts have washed out over San Luis Obispo County this year, leaving behind cirrus clouds composed of fibrous webs of ice crystals that have gently curved or straight filaments, but little rain. This photo was taken at the Point San Luis Lighthouse on Wednesday when a weak cold front washed out.

JOHN LINDSEY

For those that track rain fall each year, it will come as no surprise that so far this January-February-March period is one of the driest on record in San Luis Obispo County.

In fact, it’s the third driest since 1870 at Cal Poly (home of climatology for San Luis Obispo).

The driest January-February-March on record occurred in 1972, when only 1.9 inches of rain fell. This was in stark contrast to the 41.7 inches of rain that fell in this January-February-March time frame in 1969.

So why has it been so dry this year? A large-scale high pressure ridge has dominated our weather at a longitude that has never fluctuated far from the western edge of North America. This condition hasn’t allowed the normal winter-time storm systems to progress southward into California. However, another area of high pressure about 3,700 miles away as the crow flies may be the real culprit.

According to PG&E senior meteorologist Ted Schlaepfer, this year’s drought pattern across California is related to a strong and persistent area of high pressure in the upper atmosphere near Greenland.

The “Greenland Block” is a blocking high pressure ridge that has forced the polar jet stream southward over the Midwest and East Coast. For the majority of the winter months we have seen a “seesaw” affect causing a lasting high pressure ridge along the West Coast.

Greenland block could be related to the Pacific Decadal Oscillation in the North Pacific Ocean or another phenomenon called the Arctic Oscillation, but no really knows for sure.

To add to the uncertainty, the U.S. Climate Prediction Center is predicting that the current neutral conditions — the infamous El Nothing — will continue through summer. Neutral conditions generally don’t produce any reliable seasonal rainfall predictions along the Central Coast.

One thing for sure, even though it’s still March, many people, including Robert Lewin, Cal Fire chief for San Luis Obispo County, have noticed the grasses are already going to seed and showing yellow. Chief Lewin has kept a close eye on this year’s rainfall totals and the amount and type of vegetation in San Luis Obispo County in anticipation of bringing in their fire season staffing in early.

“When we get dry windy weather under these drought conditions it will push us into critical fire conditions early. We may be in for a long fire season,” he said.

He went on to say that “There are three factors that influence wildfires: topography, fuels (the type of vegetation), and weather. Of those three factors weather is the least predictable and most dangerous factor for firefighters to contend with. A sudden wind shift has killed many firefighters.”

To help prepare for this upcoming fire season, Cal Fire has an informative website that can be viewed at http://calfire.ca.gov/fire_prevention/fire_prevention.php. •••

Did you know? PG&E delivers some of the nation’s cleanest power. Nearly 60 percent of the electricity the company provides to customers comes from sources that are renewable and/or emit no greenhouse gases.

John Lindsey’s column is special to The Tribune. He is a media relations representative for PG&E and a longtime local meteorologist. If you have a question, send him an email at pgeweather@pge.com.

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