by Ellen Gray / BOISE, IDAHO/
Each morning Amber Soja gets up at 5:00 a.m. to check the fire weather. She’s an associate scientist from the National Institute of Aerospace based at NASA’s Langley Research Center in Virginia, one of the lead forecasters for FIREX-AQ with one of the most important jobs: distilling the information from the National Weather Service, the National Interagency Fire Center, and other satellite and model info into a short list of fires for the DC-8 to visit the next day. All by 8 a.m.
Understanding fire weather is a big part of the job. Fire weather is the term used to describe weather conditions favorable for fires to start or burn, a mixture of high temperature, low humidity, zero to low rainfall, and high winds.
“Fire weather is the potential to have the fire behavior that we want to see,” Amber said. Hot, dry and windy conditions build over the course of a day’s worth of sunshine, so that where fire weather conditions are present in the morning, fires in the same area are likely to become active in the late afternoon. And for the FIREX-AQ science team, active usually means a smoke plume to fly through.
At 10:00 a.m., Amber presents her team’s short list of fires to the science team at the daily morning briefing. This is the meeting where decisions are made about where and when to fly the DC-8. In a neat table projected on the wall, the fire short-list also takes into account the types of fuel on the ground – the second major ingredient for wildfires, and one that can change the chemistry of the plume whether its grassland or timber – as well as location, size, and what action is being taken to monitor and fight the fire, among other considerations.
While Amber is putting together the fire outlook, David Peterson from the U.S. Naval Research Laboratory in Monterey, California, is working with a team of meteorologists and forecasters to monitor and forecast weather systems. It’s a slightly amped up version of a local weather newscast, and includes current conditions and outlooks for high and low pressure systems, moisture, and cloudiness that could hamper the DC-8. By 9:00 a.m. they’re analyzing their model results, and at the 10 a.m. briefing, David shares the forecast with the science team.
He’s also on the lookout for the potential for a different type of weather – weather generated by the fires themselves.
“A fire is a heat source. It’s creating a strong updraft,” David said. The smoky air above a large, hot fire shoots upward like going up a chimney, and in the void left behind, more air is sucked in from the sides, which gets heated and lofted. When this fire-generated circulation lofts the smoke high enough, from 15,000 to 30,000 feet, and there’s moisture at the higher altitudes, pyrocumulonimbus clouds can form – also known as smoke-infused thunderstorms.
These billowing, smoke-polluted storms don’t really produce rain, but lightning strikes are possible. They can also, in some cases, loft a large smoke plume into the upper atmosphere (stratosphere), where it can circulate around the globe, similar to the impact from a volcanic eruption.
With each daily forecast, David is on the lookout for conditions that might produce pyro-clouds and thunderstorms. In the coming week, the weather over the Shady Fire looks promising, but only time – and a little luck – will tell.
UPDATE Aug 13, 2019: The DC-8 flew through a pyrocumulous cloud on August 8 generated by a fire in eastern Washington. David got to sit in the cockpit and see the cloud from the air. See the stunning pictures and read more about it at NASA’s Earth Observatory Image of the Day.