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Fuel Moisture II

posted Jul 6, 2014, 4:36 PM by Joe Christy
I wouldn't put too much faith in the the BNDC1 sensor as representing a good overview the totality of fire risk.

As I pointed out in late April, that sensor measures 10 hour, dead fuel moisture. Most of the dangerous fuel on our mountain is 100- and 1000-hour fuels, which are infeasible to measure accurately. Moreover, in most area outside the parts of the Lockheed and Martin fire footprints there is far more live fuel than dead fuel, which is by definition impossible to measure.
To reiterate, outside of burn season, when empirical observation is legal, if not always prudent, the best and most useful way to get a feel for the fire risk is is the following.
"The common rule of thumb for determining when live fuel moisture is perilously low is when it's crunchy. Take a live leaf or a small branch from a manzanita or a scrub oak and bend it with your hand. In the winter it will bend before breaking, if it breaks at all. In wildfire season, leaves crackle in your hand and sticks snap."

This week I've been out with the Ben Lomond Camp crews and their CAL FIRE captains at least part of every day working on the Cotoni Fuel Break. On Tuesday, when the mountaintop was in the clouds, the relative humidity was as high as possible. Fog is equivalent to 100% relative humidity, else the water wouldn't condense of out the air. By Wednesday afternoon, it was dry as dust again.