As the sun begins to set on the west coast, gray smoke from wildfires can be easily distinguished from white clouds. In the photo, the largest smoke plume is coming from the the Dixie Fire in Northern California. Smoke from other fires was being generated in northeast Washington, Southern Oregon, British Columbia, Northern Idaho, and Western Montana. NOAA, GOES 17.
A reporter for CNN, Rachel Ramirez, wrote an “explainer” article about some of the phenomena associated with wildfires that are part of the common parlance among wildland firefighters, but might seem strange to normal people. Some of the topics covered are fire whirls, fire tornadoes, pyrocumulus clouds, and fires “creating their own weather.”
Ms. Ramirez has quotes from Janice Coen, a scientist at the National Center for Atmospheric Research and at least one other name that will be familiar to our readers.
Here is a brief excerpt from the article:
And as climate change accelerates, these wind patterns will continue to shift.
“With the changing climate, the projected change is that the jet stream will shift towards the north,” Coen told CNN, which means that “we might see fewer of these events in California, and see more in Oregon and Washington if these wind events, the regional weather pattern, coincide with underlying dry periods in fortuitous ignitions.”
Using the Coupled Atmosphere-Wildland Fire Environment modeling system
CAWFE
The Coupled Atmosphere-Wildland Fire Environment modeling system was used to produce the video below to show how it would predict the spread of the Camp Fire that burned through Paradise, California November 8, 2018.
This simulation of the first 8 hrs of the #CampFire was created using our CAWFE model (Coupled Atmosphere-Wildland Fire Environment).
The animation will help us understand the factors that made this #fire so deadly.#Paradise#CalFire
The CAWFE modeling system combines a numerical weather prediction (NWP) model that predicts how weather varies in time and space even in complex terrain with wildland fire behavior modules. These components are connected in two directions such that the evolving wind, along with fuel properties and terrain slope, directs where the fire grows and how fast, while heat released by the fire modifies its atmospheric environment thereby creating its own weather (e.g., fire-induced winds). The model is described in Clark et al. (2004) and Coen 2005a. Coen (2013) documents the model equations.
CAWFE was developed recognizing that fires interact with the atmosphere surrounding them and that this produces many fundamental fire behaviors. Research applying CAWFE showed that fire-atmosphere interactions produce numerous wildland fire phenomena, including the commonly-observed bowed shape (below); the heading, flanks, and backing regions; fire whirls; horizontal roll vortices.
The CAWFE was developed by Janice Coen and other scientists at the University Corporation for Atmospheric Research, as well as Don Latham (formerly USFS, Missoula), Francis Fujioka (formerly, USFS Riverside), Phil Riggan (USFS), and David Packham (Bureau of Meteorology in Australia).
“Hurricane force” winds, according to the National Weather Service, are sustained winds or frequent gusts of 74 mph.
Above: Fine-scale weather model simulation (horizontal grid spacing of 370 meters) analyzing the surface wind when the Northern California fires started, 8 p.m. local time October 8, 2017. The darkest brown areas (with cross-hatching) indicate wind speeds greater than 40 m/s (~90 mph). The red shapes indicate heat from active fires first detected by a satellite (VIIRS) at 3:09 a.m. local time October 9, 2017. Simulation by Dr. Janice Coen, a Project Scientist at the National Center for Atmospheric Research in Boulder, Colorado. Simulated with the Coupled Atmosphere Wildland Fire Environment model.
(Originally published at 10:40 a.m. MDT October 30, 2017.)
More research into the weather conditions when the devastating October 8 wildfires started in Northern California indicates that hurricane force wind was one of the factors responsible for the extremely rapid spread of the fires that killed at least 43 people and destroyed more than 8,900 structures.
Dr. Janice Coen, a Project Scientist at the National Center for Atmospheric Research in Boulder, Colorado ran fine-scale weather model simulations (horizontal grid spacing of 370 meters) analyzing the wind during the time the fires started. Her research (see chart above) showed significantly higher surface wind speeds than previously thought — 75 to 90 mph just upwind of the major fires.
CAL FIRE has not released the causes of the October 8 conflagrations, but at about the same time firefighters were first responding to numerous fires, they also received multiple calls about fallen power lines and electrical transformers exploding.
California law dictates that power lines are supposed to be able to withstand 56 mph.
In an email Dr. Coen told us more about the October 8 wind simulation and her research related to fire weather:
“These early simulations suggest that within a wide area of strong winds, these small, local bands of extreme winds occurred where winds were perpendicular to the local ridge. And, that the location of the peaks and their peak speeds evolved throughout the event as the wind direction changed, in part due to the high pressure over the Great Basin moving along.
“I don’t have a lot of confidence that we’d be able to find evidence to prove or disprove if/when a particular simulated wind speed maximum occurred. And, although there is a lot of theoretical and laboratory work on stably stratified flow over objects, this three-dimensional terrain is too complicated to apply much of that.
“We’ve seen a sequence of devastatingly destructive fire events each driven by strong wind events – 2007 fires in southern California driven by Santa Anas, surprising destruction from a mountain downslope wind-driven fire in Gatlinburg, TN, and now this – yet fine-scale investigations of the mechanisms producing the peak winds and how they are distributed, particularly in relation to potential ignition sources, don’t really exist. And, though our forecast models may indicate strong gusty winds are possible, explicitly predicting how extreme the winds might be and where the most dangerous spots are with the detail shown here is beyond their capabilities.
“I hope to learn and share more about the mechanics of these events by visualizing these simulations, so we can see inside these events, prepare and anticipate, contribute to firefighter awareness and safety (as Diablo winds in general are a regional fire issue), and perhaps help potential ignition sources such as utilities manage the risk.”
Fine-scale weather model simulation (horizontal grid spacing of 370 meters) analyzing the weather during the time the Northern California fires started, 8 p.m. local time October 8, 2017. The darkest brown areas indicate wind speeds greater than 40 m/s (~90 mph). Simulation by Dr. Janice Coen, a Project Scientist at the National Center for Atmospheric Research in Boulder, Colorado.
File photo of power lines near a wildfire in Portugal, 2012.
Following the Witch Creek, Guejito, and Rice Canyon fires that destroyed more than 1,300 homes and killed two people in Southern California in 2007, state officials began attempting to force the utility companies to produce maps designating areas where their power lines present the highest risk for starting wildfires. The three large fires in 2007 were sparked by issues with lines operated by San Diego Gas and Electric.
CAL FIRE has not released the causes of the huge fires that started in Northern California October 8 during very strong winds, but at about the same time firefighters were first responding to numerous fires, they also received multiple calls about fallen power lines and electrical transformers exploding. In the next week, the stock price of the company that provides electrical service for large areas of Northern California, Pacific Gas and Electric, dropped 22 percent.
According to the Mercury News, PG&E has been fighting the efforts to map powerline risk areas since 2007. Below is an excerpt from their article:
A review of the mapping project by the Bay Area News Group shows that utilities have repeatedly asked to slow down the effort and argued as recently as July that, as PG&E put it, certain proposed regulations would “add unnecessary costs to construction and maintenance projects in rural areas.”
On Oct. 6, two days before the start of the deadliest outbreak of wildfires in California history, two administrative law judges assigned to oversee the project granted yet another delay at the request of PG&E and other utilities.
[…]
[PG&E] claimed there was no evidence that wildfires had been caused by poles not being able to withstand high winds.
The Northern California fires killed at least 43 people and destroyed about 8,900 structures.
Dr. Janice Coen, a Project Scientist at the National Center for Atmospheric Research in Boulder, Colorado ran fine-scale simulations (horizontal grid spacing of 370 meters) analyzing the wind during the time the fires started. Her research showed significantly higher surface wind speeds than previously thought — 75 to 90 mph just upwind of the major fires.
California law dictates that power lines are supposed to be able to withstand 56 mph.
Pioneer Fire northeast of Boise, Idaho, August, 2016. USFS photo.
High Country News has an excellent article written by Douglas Fox that looks under the hood, so to speak, at the science that causes wildfires to burn the way they do. There are forces, unknown until the last decade or two, that are major influences on the spread of a fire, such as the 100 mph flamethrower-like jets of flame that may have contributed to the deaths on the 1994 South Canyon fire near Glenwood Springs, Colorado.
Mr. Fox writes in illuminating detail about state-of-the-art research being conducted by Janice Coen, David Kingsmill, Craig Clements, Mark Finney, Michael Reeder, and Brian Potter, as well as legacy research done by the the U.S. military in the 1940s that provided data on how to design incendiary bombs to burn down many of the buildings in Hamburg, Germany on July 27, 1943 in order to demoralize the workers in Germany’s critical U-boat industry.
Most of the article is about recent research on wildfires, but here is an excerpt about the military’s work in the 1940s in northwest Utah that facilitated the attack on Hamburg by the British that killed at least 42,000 people.
…The U.S. Army’s Chemical Warfare Service had commissioned Standard Oil Development Company to construct a row of steep-roofed European-style apartment buildings. Erich Mendelsohn, an architect who had fled Nazi Germany, specified every detail: 1 1/4-by-2-inch wood battens, spaced 5 7/8 inches apart, to hold the roof tiles; 1-inch wood flooring underlain by 3 1/2-inch cinderblocks, and so on — all to replicate the dwellings of German industrial workers. The wood was maintained at 10 percent moisture to mimic the German climate. Rooms were outfitted with authentic German curtains, cabinets, dressers, beds and cribs — complete with bedding — laid out in traditional floor plans.
Then, military planes dropped various combinations of charges on the buildings, seeking the most efficient way to penetrate the roofs and lace the structures with flame.
Those experiments offered clues on what factors could cause firestorms. And in the years following World War II, scientists would study Hamburg and other bombing raids to derive basic numbers for predicting when a firestorm might form: the tons of munitions dropped per square mile, the number of fires ignited per square mile, and the minimum area that must burn. They concluded that Hamburg’s unusually hot weather set the stage for the firestorm, by making the atmospheric layers above the city more unstable and thus easier for a smoke plume to punch through. Scientists theorized that this powerful rise had drawn in the winds that whipped the flames into even greater fury.
NASA released a video this week that explains some of the features of the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite that was launched October 28, 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the satellite is a 22-band radiometer designed to collect infrared and visible light data to observe wildfires, movement of ice, and changes in landforms. It has a resolution of 375 meters, much better than the MODIS satellite data with 1,000-meter resolution. The MODIS was launched in 1999.
The combination of the VIIRS data (that is updated twice a day), weather forecasts, and fire behavior modeling software developed by Janice Coen and Wilfrid Schroeder, can result in more useful fire spread forecasts for fire managers.
