Driving in the rain to Paso Robles on Saturday to participate in the 2011 Endeavour Institute STEM Education (science, technology, engineering and math) Balloon Fest at Tobin James Cellars, I kept thinking how out of whack our weather seems to be lately.
These students from the North County had to release their tethered balloons with their payload of science experiments in the rain. Normally at this time of the year, the North County would be clear and dry with temperatures well in the 80s or even the 90s.
Our climate is classified as Mediterranean, meaning the annual rainfall pattern includes a dry summer and wet winter. The predominant weather feature is the Eastern Pacific High — an area of high pressure over the northeastern Pacific Ocean. The clockwise circulation around this high brings cooler and relatively drier air from the Gulf of Alaska and produces the weather conditions we appreciate along the Central Coast.
Along the East Coast, the predominant weather feature during the summer is the Bermuda High — a semipermanent area of high pressure over the Atlantic Ocean near the Bermuda Islands. The clockwise circulation around this high brings warm, humid air from the Gulf of Mexico and the Caribbean Sea and produces the three H’s — heat, humidity and haze. Often, the southeastern part of our country gets little or no relief from the hot and humid conditions. So far this spring, the eastern part of the country has seen record-breaking warm temperatures and tornado activity.
Usually by June, the Eastern Pacific High has shifted northward, keeping the storm track far to the north. The average total precipitation for June is only 0.07 inches in San Luis Obispo.
Since the year 2000, it has only rained three times in June at the Diablo Canyon Power Plant. On June 5, 2009, a slow-moving and vigorous upper-level low-pressure system produced 0.37 inches at the power plant and 0.44 inches at SLO Weather.com and in Los Osos. The wettest June on record occurred in 1991 when 0.80 of an inch fell in San Luis Obispo.
So far this spring, a strong area of high pressure has remained over western Canada. This condition has probably caused the eastern Pacific high to shift farther to the west out over the Pacific than normal. A few climatologists are blaming the residual effects of La Niña and the negative phase of the Pacific Decadal Oscillation, a long-lived El Niño-like pattern for the weather pattern.
Regardless, this weather pattern has allowed a series of cold Gulf of Alaska low-pressure systems to move southward along the eastern side of the Eastern Pacific High and down the California coast producing below-normal May and early June temperatures across much of California and above-normal rainfall.
The below-normal temperatures have slowed the snowmelt of this year’s nearly record-breaking snowpack.
“This year’s melt may extend past that of 1998 which was a former record snow year for Northern California and could very well extend into July,” said Gary Freeman, a Pacific Gas and Electric Company water-management specialist.
“This type of cool, snowy late-spring weather is great for growing glaciers on the slopes of Mount Shasta. These glaciers have increased in size in recent years due to the increased moisture available with warming temperatures. Mount Shasta has excellent orographic cooling and can take advantage of the increased moisture that accompanies a warming climate,” he said.
Not only have the below-normal temperatures slowed the snowpack melt, but they have also affected many farmers throughout California.
“The below-normal temperatures have slowed the ripening of many fruits in the San Joaquin Valley this year,” said a local grocer, John Spencer.
With all this being said, The National Climate Prediction Center is forecasting normal seasonal temperatures in San Luis Obispo County this summer. However, as you move farther eastward, the San Joaquin Valley is forecast to have above-normal temperatures. A greater chance for above-normal seasonal temperatures is forecast in southern Nevada and Arizona.
This week’s forecast
A tightly wound 1,006- millbar low-pressure system will gradually dissipate and move eastward over the Central Coast today. This system will continue to give widely scattered rain showers, at times heavy, through tonight. Breaks in the cloud cover today will allow the strong June sun to produce surface heating creating an unstable atmosphere and the chance for thunderstorms.
A few rain showers will linger into Monday morning as the storm will slowly exit the region. Snow is expected in the higher elevations of the Sierra into Monday above 7,500 feet.
The northwesterly (onshore) winds and dry weather will return Tuesday. Gradually warmer temperatures will occur through the week with Paso Robles reaching the high 80s by Friday.
Surf and sea report
This morning’s 6- to 8-foot west-southwesterly (260-degree deep-water) sea and swell (with a 7- to 11-second period) will decrease to 3 to 5 feet by tonight and will continue at this height and period through Monday.
Increasing northwesterly winds will generate a 4- to 6-foot northwesterly (300-degree deep-water) sea and swell (with a 7- to 13-second period) Tuesday.
A 5- to 7-foot northwesterly (290-degree deep-water) swell (with a 10- to 12-second period) is forecast along our coastline Wednesday through Thursday.
Strong to gale force (25- to 38-mph) northwesterly winds will generate 6- to 8-foot northwesterly (310-degree deep-water) sea and swell (with a 7- to 11-second period) Friday through next Sunday.
Arriving from the Southern Hemisphere:
A 1- to 3-foot Southern Hemisphere (225-degree deep-water) swell (with an 18- to 20-second period) is forecast along our coastline Tuesday, increasing to 2 to 3 feet (with a 16- to 18-second period) Wednesday. Seawater temperatures will range between 51 to 53 degrees through Monday, decreasing to 50 to 52 degrees Tuesday and will remain at this level for Friday.
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John Lindsey, media relations representative for PG&E and local weather expert, has lived along 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.