Relative humidity, not rain, helps contain fire
Published 5:59 am Sunday, June 22, 2008
Dry conditions helped spark Evans Road wildfire
By GREG KATSKI
While many have been praying for rain to quell the Evans Road fire, relative humidity could play even more of factor in fire containment.
John Jacobsaon, senior meteorologist with the National Weather Service, attributes the recent advances in containment of the fire partly to “a shift in the weather pattern.”
When the fire started on June 1, it was aided by a prolonged heat wave. The high temperatures and low relative humidity were uncommon to the area “for this time of year,” according to Jacobson.
The current weather pattern is considered “tropical” and much more beneficial in fighting a wildfire, even a ground fire.
One tool that meteorologists use to track wildfire conditions is “the probability of ignition.” The current probability of ignition is 30 percent, down from over 80 percent just a few days ago, according to Jacobson.
This is especially important in controlling containment lines. Embers have been causing spot fires outside the lines, but this is much less likely with the high relative humidity.
The fire is less effective in spreading with high relative humidity, according to Bruce MacDonald, an information officer with the IMT.
It also reduces the potency of the pocosin fuels, which sustain the ground fire.
The shift in weather gives those working on the fire some much needed down time.
The high relative humidity, coupled with scattered thunderstorms, such as those that hit the fire early Saturday morning, will help reduce the fire.
According to Jacobson, the western edge of the fire area got a quarter-inch of rain on Saturday.
The area will receive more relief in coming days, Jacobson said.