With last year's wildfire season dominating headlines for being the deadliest and most destructive wildfire season on record in California – with over 8,500 fires burning almost 2 million acres – public interest in the phenomenon and the importance of public safety awareness is understandably increased. As such, here is a quick summary of everything you should know about the meteorological causes and impacts of wildfires and extreme fire weather.
What is fire weather?
Fire weather describes meteorological and environmental conditions that make the spark and spread of wildfires more likely. Conducive weather conditions are low relative humidity (usually less than 25%), high winds and lightning. There also needs to be an environmental source of fuel, such as dry brush, dry forest or drought-stricken areas.
How can damage be limited?
The clearing of tall grasses and bushes (referred to as ladder fuels) from urban-to-forest transition areas can prevent small grass fires from spreading into the tree canopy and becoming larger wildfires, which are more difficult to contain.
What warnings, watches and alerts can be expected?
The National Weather Service issues red flag warnings, fire weather watches and alerts about extreme fire behavior.
Red flag warnings indicate that conditions are favorable for fires to start. These warnings urge the inhabitants of a warned area to take action and not create conditions that may spark a wildfire (like using open flames, smoking cigarettes, etc).
A fire weather watch calls for the inhabitants of the areas under that watch to be prepared in the event of a wildfire. Under a watch, conditions for wildfires may become favorable but are not yet occurring. Extreme fire behavior means that fires are occurring and are likely to become uncontrollable.
Fire weather conditions can impact summertime roadway operations. Maintenance personnel should be aware that mowing dry areas of grass could create sparks and start a fire, especially during a red flag warning. Many agencies will cease their mowing activities until the warning has been lifted.
Is fire weather only hazardous when fire is present?
The dangers from fire weather are not always isolated to the fires themselves. The aftermath of fires can be just as dangerous. An area that has been burned by a wildfire is identified as a burn scar. Areas with burn scars have a higher likelihood of flooding and landslides. These areas must be monitored by roadway maintenance professionals as rainy conditions, especially heavy rain, can cause flash flooding or landslides in a short amount of time.
The Bottom Line
Wherever your operations take place, fire weather conditions can occur. Stay up to date on fire weather watches and warnings from the National Weather Service. Take appropriate action to mitigate the risk of sparking a fire. If fires have occurred in your area, especially along roadways, remember to monitor those areas during and after rain events, particularly near burn scars.
About the Author:
Brianna Kump is a road weather meteorologist at Iteris.