Chris Mackie posted this video on July 15, 2018 of spectacular fire behavior at a wildfire on the Arizona side of the Colorado River near Blythe, California. It is not uncommon to see dust devils and fire whirls during unstable weather conditions on a fire, but as you can see beginning at about 1:10 the rotating vortex over this fire intensifies into what some might call a fire tornado (or “firenado”) as trees are uprooted and debris is thrown into the water as it moves over the river (and transforms into a waterspout?).
“The news media sometimes calls any little fire whirl a “fire tornado, or even a “firenado”. We found out today that these and related terms (except for “firenado”) were, if not founded, at least documented and defined in 1978 by a researcher for the National Weather Service in Missoula, David W. Goens. He grouped fire whirls into four classes:
Fire Devils. They are a natural part of fire turbulence with little influence on fire behavior or spread. They are usually on the order of 3 to 33 feet in diameter and have rotational velocities less than 22 MPH.
Fire Whirls. A meld of the fire, topograph, and meteorological factors. These play a significant role in fire spread and hazard to control personnel. The average size of this class is usually 33 to 100 feet, with rotational velocities of 22 to 67 MPH.
Fire Tornadoes. These systems begin to dominate the large scale fire dynamics. They lead to extreme hazard and control problems. In size, they average 100 to 1,000 feet in diameter and have rotational velocities up to 90 MPH.
Fire Storm. Fire behavior is extremely violent. Diameters have been observed to be from 1,000 to 10,000 feet and winds estimated in excess of 110 MPH. This is a rare phenomenon and hopefully one that is so unlikely in the forest environment that it can be disregarded.”
Technosylva has released a new free app for smart phones that can help predict fire behavior. It is called Wildfire Analyst Pocket and is available for Android phones. It will soon be on the Apple app store as well.
In a video filmed May 21, 2018, the president of the company, Joaquin Ramirez, introduces us to the app.
Above: screenshot from the Wall Fire time-lapse video below.
This time-lapse video of the Wall Fire condenses one hour of high intensity fire behavior into a one minute video. It was photographed using the camera system operated by the Nevada Seismological Lab between 7 p.m. and 8 p.m. on July 8, 2017, the day after the fire started. Since then it has burned 5,800 acres and destroyed 41 homes and 55 other structures southeast of Oroville, California.
If you are interested in wildland fire behavior, you may be fascinated by the occasionally counter-rotating as well as single horizontal and vertical vortices as the fire rapidly spreads across the landscape.
This phenomenon is important to firefighters because of the extreme fire behavior that can put personnel in immediate danger.
The Southern California Geographic Area Coordination Center has issued a Fuels and Fire Behavior Advisory for the central and southern areas of California due to a heavier than usual grass crop brought on by above average winter rains. Because of the vegetation and climate in Southern California it seems like we hear similar warnings often — heavy rains bring lots of flashy grass fuels, and a dry winter results in low fuel moistures. An average winter can mean typical fire potential, which in this area can still mean large devastating wildfires. But as we often say, the most important factor that affects the number of acres burned is the weather during the fire season.
Below is an excerpt from the Advisory. Following that is the entire document.
“Due to the heavy winter rains, a significant grass crop has developed across much of California in the recent months. These light, flashy fuels have now cured across most of the southern and central portions of the state, which has led to a significant increase in fire activity across much of the Southern California Geographic Area. Despite the volatility of these grass fires, the heavier fuels are less supportive of fire as moisture levels in the larger diameter materials is near normal for this time of year. In addition, live fuel moisture remains above average in many areas. Therefore, while significant acreage consumption will continue to occur on future fires within the grassy fuel beds, large fires among the heavier fuels are less likely.”
Thanks and a tip of the hat go out to Ken. Typos or errors, report them HERE.
Above: The U.S. Forest Service tests burning pine straw in an IBHS wind tunnel earlier this year. Screen grab from IBHS video.
The Insurance Institute for Business and Home Safety (IBHS) will host a live wildfire-related event on Facebook Wednesday November 9 at 10:30 a.m. EST. They have not provided a ton of information about but it will “open up the curtain a bit on wildfire studies”. (Link to the IBHS Facebook Page.)
Dr. Steve Quaries will discuss the wildfire research that they have been doing in the huge wind tunnel. In 2011 using 105 huge fans and spark-generators, they launched embers at a structure to demonstrate what can happen when a wind-driven fire approaches a poorly prepared structure.
The video below shows embers igniting flammable material on and around a structure in the IBHS wind tunnel.
Earlier this year the U.S. Forest Service used the facility to study the relationship between wildland fire rate of spread and wind speed used in the U.S. wildland fire behavior decision support systems. Previous experiments have been conducted in the Missoula Fire Sciences Laboratory wind tunnel that is more limited in size and wind speed than the IBHS wind tunnel.
This research is a collaborative effort with researchers at UNC Charlotte, University of Maryland, University of Texas Austin, and USDA Forest Service, and is funded by the Joint Fire Science Program.