After 30 years of fighting fires throughout California, Cal Fire Battalion Chief Chad Zrelak keeps keep a wary eye on the sky. So far this year, San Luis Obispo County has been spared major wildfires, but many people have vivid memories of years past, including the Highway 41 Fire.
So far this summer a persistent upper-level, low-pressure trough in the upper reaches of the atmosphere has allowed cool and moist air from the Pacific to penetrate farther into the coastal valleys and the North County than normal, producing one of the coolest summers on record in western San Luis Obispo County.
Many mornings this summer have seen measurable precipitation from the heavy drizzle along our immediate coastline.
This in turn has produced a quiet fire season with moisture contents of vegetation higher than average. The National Fuel Moisture Database indicates black sagebrush, a common shrub in the Irish Hills and throughout the western United States, had a moisture content of 101 percent this August compared to about 96 percent in August of 2008 and 2009.
Vegetation or fuel moisture content is the percentage of the total weight of the plant including its water content divided by its oven-dry weight. Moisture content is often greater than 100 percent because the water in a plant may weigh considerably more than the dry weight itself.
The greater the amount of water in the plant, the more heat will be required to evaporate the moisture before it will burn. The role of vegetation or fuel moisture, along with meteorological conditions, is critical in determining potential fire risk.
Another cause of the quiet fire season has been San Luis Obispo County’s near total lack of the North American monsoon, which can bring lightning. On July 11, subtropical moisture interacting with an upper-level low off our coastline produced a few scattered rain showers and thunderstorms throughout San Luis Obispo County. A particularly intense band of thunderstorms moved through New Cuyama and sparked a fire that was quickly contained.
However, the cool weather pattern could change in a hurry if the position of the jet stream changes. Last year’s above-normal rainfall produced abundant vegetation and California’s wildfire season typically peaks during the late summer and early fall months.
Serious wildfire risk still exists, and climate records show that lightning storms become more prevalent in California during this time.
“The annual grasses are more abundant this year, allowing more fire fuels to exist,” Zrelak said. He added that common causes of wildfires are “dragging metal on paved roads, such as a chain or rebar, grinding or welding with inadequate clearance, burning in burn barrels. Burn barrels are now illegal in this county.”
Fire prevention and protection information can be found at www.fire.ca.gov. For other emergency preparedness tips, go to www.pge.com.
Today will be a transition day as high pressure builds in the upper atmosphere from the east, producing warmer temperatures in the North County, coastal valleys and southwesterly facing (Avila Beach and Cayucos) beaches. Fresh to strong (19 and 31 mph) northwesterly (onshore) winds will keep the northwesterly- (Los Osos and Morro Bay) facing beaches cooler.
This area of high pressure will also squash the marine layer, allowing for abundant sunshine during the late morning and afternoon hours along the coast.
Today’s temperatures will range from the mid- to high 60s along the northwesterly facing beaches and mid- to high 70s along the southwesterly-facing beaches. The coastal valleys will also range from the mid- to high 70s, with the North County reaching the low 90s. To the east, California Valley is forecast to reach the low 100s.
Monday will see the winds shift out of the north. This condition will really warm things up. Expect highs in the 80s near the coast, 90s in the coastal valleys, and the low 100s in the interior of San Luis Obispo County.
Southerly winds in the mid- to upper levels of the atmosphere will bring in monsoon moisture from Mexico later on Monday through Wednesday, producing variable mid- to high-level clouds and a chance of thunderstorms over the Santa Lucia Mountains.
Tuesday will be very similar to Monday with winds blowing from the north in the morning. But by Tuesday afternoon, the northwesterly (onshore) winds will increase, and this will mark the beginning of the end of the short heat wave.
On Wednesday, the northwesterly winds will pick up, which will cool the coastal valleys. It will take through Thursday and Friday to finally see the cool air make it well inland.
Surf and sea report
Increasing northwesterly (onshore) winds will generate a 4- to 6-foot northwesterly (320-degree deep-water) sea and swell (with a 5- to 11-second period) this afternoon and will remain at this height and period through Thursday.
Strong to gale force (25 to 38 mph) northwesterly winds along the entire Northern and Central California coastline will generate a 6- to 8-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 11-second period) on Friday through next Sunday.
Arriving from the Southern Hemisphere: A series of storms developed about 2,000 miles to the west of Chile last week. Today and tomorrow’s 2- to 3-foot Southern Hemisphere (195-degree deep-water) swell (with a 16- to 18-second period) will be overlapped by another 3- to 4-foot Southern Hemisphere (190-degree deep-water) swell (with an 18- to 20- second period) on Tuesday.
This swell will peak on Wednesday at 3 to 5 feet (with a 15- to 17-second period), gradually decreasing on Thursday and Friday.
Seawater temperatures will range between 52 and 55 degrees through Friday, decreasing next weekend.