[californiadisasters] Wildfire threat could soar if weather warms

Wildfire threat could soar if weather warms

By John Lindsey - SLO Tribune

Published: Sunday, Aug. 22, 2010

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.

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Read entire article here: http://www.sanluisobispo.com/2010/08/21/1259149/wildfire-threat-could-soar-if.html

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