The first few days of the Virginia Spring Fire Season have already produced a rash of fires across the area. Last Saturday’s fire at Ragged Mountain produced a smoky hue to the sky that was seen as far away as Waynesboro. Speaking of the Valley, it was Augusta and Rockingham Counties that were particularly hard hit with numerous fires. With a rainfall deficit over 17 inches below normal since the start of 2010 and very little rain ahead for the next seven days, these dry times will only breed more fires which will have the potential to eat up more wood- and grasslands in the coming months.
There are several factors that affect the wildfire danger for a particular region. The first of those factors is the dryness of the air. Low relative humidities – or air with a low moisture content – will yield a much faster burn. The water in air acts as a inhibitor; as a result, humid and muggy conditions are favorable in either fighting fires or preventing. Another factor is the fuel moisture. In a similar fashion as dry air, dry fuels will not have water inside to slow the burn. Therefore, grasslands, brushlands, and drought-stricken areas are prime breeding grounds for fires. The third major factor in determining wildfire danger is the speed of the winds. Simply put, faster winds will drive fires. It should also be noted that fires will grow faster when burning up a hillside as opposed to burning down a hillside.
In the case of the fires we saw this past weekend, all of the ingredients were in place. Very dry air with relative humidities (RHs) below 20%, combined with fuel moistures below 6% and winds over 50 miles per hour, led to fast-spreading fires that burned for over 24 hours in some instances. Fortunately, some breaks in the dangerous conditions are ahead as there will be rain late tonight into tomorrow, and again late Thursday into Friday, though we still need a LOT more to make up ground in our deficit.
The unfortunate sides of these drought conditions are that dryness breeds dryness, and it takes a LOT to overcome. I was always taught in my college classes: “when in drought, leave rain out.” This means that it’s very difficult to have a very sudden end to a particular pattern; drought-busting rains rarely happen quickly. Even so, heavy rains in a drought would merely run off the hard, dry ground, proving to be ineffective. It’ll take a lot of steady, soaking rain over several weeks to ease us of our dry times. Sadly, the wet pattern we so desperately need is not looking to happen anytime soon.
Some pictures of the Dick Woods Road fires I took on Saturday afternoon can be found here.
Reminder: open burning in Virginia is now illegal from midnight until 4:00 PM until April 30. Be safe!
3, 2, 1, fade out…
~Chief Meteorologist Travis Koshko
(This blog written while listening to "Fire" by Jimi Hendrix.)